Misumena vatia (Clerck 1757)

Misumena vatia és una espècie d'aranya araneomorf de la família Thomisidae, bastant comuna en tota Europa i present a Àsia i Amèrica del Nord. El mascle mesura entre 4 i 5 mm mentre que la femella aconsegueix 10 mm.

Freqüentment associada amb el Solidago, que atreu molts insectes als quals caça i devora. Viu en les flors, especialment les de color blanc i groc. El seu abdomen és arrodonit i es va allargant cap a la part posterior. El mascle és alguna cosa més fosc que la femella, encara que l'espècie és d'un color molt variable, blanc, crema, groc o verd, segons la flor en la qual caça (homocromia).

Běžník kopretinový (Misumena vatia) je pavouk spadající do čeledi běžníkovití (Thomisidae). Je velmi hojný ve střední Evropě, zdržuje se na suchých loukách, zahradách a poblíž polních cest.

U tohoto druhu běžníka jsou nápadné rozdíly mezi pohlavími (dimorfismus) . Zatímco samice může dosáhnout velikosti až 10 mm, samec je nanejvýš 4 mm dlouhý. Samice je barevně velmi proměnlivá, projevuje se zde paleta od bílé, přes žlutou až k zelené, po stranách zadečku se mohou vyskytovat červené pruhy. U samců je zbarvení jednotné – hlavohruď je tmavě hnědá s úzkým světlým podélným pruhem, zadeček je kontrastně bíle a hnědě pruhovaný, na rozdíl od samice jsou nohy vždy světle a tmavě proužkované.

Běžník kopretinový číhá na svou kořist většinou na květech rostlin, může se ale vyskytovat i na listech. Své zbarvení obvykle přizpůsobuje barvě podkladu – tento proces se uskutečňuje na základě přesunu tělesných pigmentů hlouběji do těla. Této barevné proměny, která je řízena zrakem běžníka, je schopná jenom samice, přičemž tento proces trvá několik dní, než je zcela dokončen. Zaměnit se dá za běžníka květinového, od kterého se liší oblým zadečkem. B. květinový má na zadečku výrazné růžky.

Běžník kopretinový

Běžník kopretinový – samice

Odkazy

Literatura

• Zoologická encyklopedie – pavoukovci a jiní bezobratlí. Praha: Knižní klub, 2003.

Externí odkazy

• Obrázky, zvuky či videa k tématu běžník kopretinový ve Wikimedia Commons
• Článek na www.european-arachnology.org, česky
• Běžník kopretinový na biolibu
• běžník kopretinový na prirodakarlovarska.cz

Veränderliche Krabbenspinne mit Honigbiene als Beute

Männchen

Weibchen mit Beute

Vorderkörper eines Weibchens

Die Veränderliche Krabbenspinne (Misumena vatia) ist eine Spinnenart aus der Familie der Krabbenspinnen (Thomisidae). Die Art ist in Mitteleuropa weit verbreitet. Die Veränderliche Krabbenspinne wurde zur Spinne des Jahres 2006 gewählt.

Merkmale

Die Art zeigt einen starken Geschlechtsdimorphismus bezüglich Größe und Färbung. Männchen erreichen nur eine Körperlänge von 4 mm, während die Weibchen bis zu 10 mm lang sind. Das Männchen hat einen schwärzlichen Vorderkörper (Prosoma); der Hinterkörper (Opisthosoma) ist weiß bis gelblich gefärbt und zeigt zwei dunkle Längsstreifen. Die beiden vorderen Beinpaare sind breit schwarz und braun geringelt, die beiden hinteren Beinpaare zeigen die Grundfarbe des Opisthosomas.

Bei den Weibchen variiert die Färbung des gesamten Körpers zwischen leuchtend gelb, gelbgrün und weiß. Sie können zur Tarnung ihre Körperfarbe aktiv wechseln. Die Seiten des Hinterkörpers tragen häufig zwei rote Längsstreifen.

Verbreitung und Lebensraum

Die Art besiedelt die arktischen bis subtropischen Zonen der Holarktis von Irland und Portugal bis Japan sowie Amerika von Alaska bis zur Südgrenze der USA. Sie kommt mit Ausnahme Islands in ganz Europa vor.^[1] Die bisherigen Funde für Deutschland deuten eine annähernd flächendeckende Verbreitung im südlichen und mittleren Teil des Landes an, während die Art nördlich der Mittelgebirge deutlich seltener gefunden wird.^[2]

Die Art bewohnt offene, blütenreiche Lebensräume aller Art. Adulte Tiere können von Mai bis Juli angetroffen werden.

Ernährung

Zum Beutefang hält sich die Veränderliche Krabbenspinne auf Blüten auf. Sie ist in der Lage, die Körperfarbe an die jeweilige Blütenfarbe anzupassen. Allerdings sind zu diesem Farbwechsel nur adulte Weibchen befähigt. Der Farbwechsel wird dabei über den Gesichtssinn gesteuert. Bei einer Gelbfärbung wird ein flüssiger, gelber Farbstoff in die Epidermiszellen eingelagert, während die Weißfärbung auf die Verlagerung des Pigments ins Körperinnere zurückzuführen ist. Der gelbe Farbstoff kann bei einem längeren Aufenthalt auf weißen Blüten auch teilweise mit dem Kot ausgeschieden werden.

Die Beute von Misumena vatia besteht aus blütenbesuchenden Insekten aller Art, z. B. Schwebfliegen, Bienen, Wespen, Schmetterlingen oder kleineren Käfern. Diese sind oft um ein Mehrfaches größer als die Spinne. Diese ergreift ihre Beute blitzschnell mit den beiden kräftigen und stark vergrößerten Vorderbeinpaaren und tötet sie meist durch einen offensichtlich sehr schnell wirkenden Biss in den Hinterhals.

Fortpflanzung

Die Paarung erfolgt im Frühsommer. Wenn ein Männchen ein Weibchen gefunden hat, klettert es von vorn auf dessen Rücken. Zur Kopulation klettert es über das Hinterende des Weibchens auf dessen Bauchseite und führt in einer Bauch-an-Bauch-Position abwechselnd seine Pedipalpen in die Geschlechtsöffnung des Weibchens ein. Danach klettert es wieder auf den Rücken des Weibchens, um dann nach einer Pause erneut zu kopulieren. Schließlich verlässt das Männchen das Weibchen. Zur Anlage des Eikokons werden offenbar Verstecke abseits der Blüten aufgesucht. Die Jungspinnen überwintern am Erdboden.

Gefährdung

Die Art ist weit verbreitet und in geeigneten Habitaten mittelhäufig. Sie wird in Deutschland in der Roten Liste als „ungefährdet“ eingestuft.

Quellen

Literatur

• Heiko Bellmann: Kosmos Atlas Spinnentiere Europas. 3. Aufl., 2006. Kosmos, Stuttgart. ISBN 978-3-440-10746-1
• Ralph Platen, Bodo von Broen, Andreas Herrmann, Ulrich M. Ratschker & Peter Sacher: Gesamtartenliste und Rote Liste der Webspinnen, Weberknechte und Pseudoskorpione des Landes Brandenburg (Arachnida: Araneae, Opiliones, Pseudoscorpiones) mit Angaben zur Häufigkeit und Ökologie. Naturschutz und Landschaftspflege in Brandenburg 8, Heft 2 (Beilage); 1999.

Einzelnachweise

1. ↑ Karte zur weltweiten Verbreitung der Veränderlichen Krabbenspinne von der British Arachnological Society
2. ↑ Atlas der Spinnentiere Europas: Nachweise von Misumena vatia

Weblinks

– Sammlung von Bildern, Videos und Audiodateien

Misumena vatia im World Spider Catalog

• Weiterführende Informationen und Fotos auf www.natur-in-nrw.de

Misumena vatia is a species of crab spider with a holarctic distribution. In North America, it is called the goldenrod crab spider or flower (crab) spider,^[1] as it is commonly found hunting in goldenrod sprays and milkweed plants. They are called crab spiders because of their unique ability to walk sideways as well as forwards and backwards. Both males and females of this species progress through several molts before reaching their adult sizes, though females must molt more to reach their larger size. Females can grow up to 10 mm (0.39 in) while males are quite small, reaching 5 mm (0.20 in) at most. Misumena vatia are usually yellow or white or a pattern of these two colors. They may also present with pale green or pink instead of yellow, again, in a pattern with white. They have the ability to change between these colors based on their surroundings through the molting process. They have a complex visual system, with eight eyes, that they rely on for prey capture and for their color-changing abilities. Sometimes, if Misumena vatia consumes colored prey, the spider itself will take on that color.

Misumena vatia feed on common insects, often consuming prey much larger than themselves. They use venom to immobilize their prey, though they are harmless to humans. They face threats due to parasites and larger insects. For Misumena vatia, survival depends on the choice of hunting site. The spiders closely monitor multiple sites to see if others nearby are frequented by greater numbers of potential prey. The primary sex ratio is biased toward females. Females are stationary and choose a flower to settle on, while males cover great distances searching for mates. Females do not emit pheromones, rather, they leave "draglines" of silk behind them as they move, which males follow. Females live longer than males, on average. After mating, females guard their nests until the young have hatched, after which they die.

Taxonomy and phylogeny

The species Misumena vatia was first described by Swedish arachnologist and entomologist Carl Alexander Clerck in his book Aranei Svecici.^[2] Misumena vatia belongs to the family Thomisidae, or spiders known as crab spiders. The family includes more than 2000 species, which are found all over the world.^[3] The genus Misumena includes many other species which are found worldwide.^[4] Misumena vatia falls into the Thomisus clade. Other clades in the family Thomisidae include the Borboropactus clade, the Epidius clade, and the Stephanopis clade.^[5]

Similar species

Close relatives include Mecaphesa asperata, which is also found in North America, as well as Central America and the Caribbean. It is similar in size and shape but is light-gray to brown with pink stripes on the abdomen and cephalothorax. It is also coated with hairs that are short and stiff.^[6]

Similar species of the Misumenoides and Misumenops genera tend to be found south of Misumena vatia’s home range, but some species, such as Misumenoides formosipes, are found in North America as well. Philodromidae is a closely related family of wandering spiders.^[7] These spiders differ from those in the family Thomisidae in that their front legs are of a similar length as their back legs. Thus, their hunting style is quite different.^[3][8]

Description

This species has a wide, flat body that is short and crab-like. It can walk sideways in addition to being able to move forward and backward. Of its eight legs, the first two pairs are the longest. These sets of legs are usually held open, as the spider uses them to capture its prey. Misumena vatia is harmless to humans, as its fangs are not powerful enough to penetrate human skin and its venom is too weak to harm larger animals.^[1]

Color

These spiders may be yellow or white. This ultimately depends on the flower on which they are hunting (active camouflage). Younger females especially, which may hunt on a variety of flowers such as daisies and sunflowers, have a strong tendency to adapt to the color of the surrounding flower. However, the color-changing process is not instant and can require up to 25 days to complete.^[9] Older females need large amounts of relatively large prey to produce the best possible clutch of eggs. In North America, they are most commonly found in goldenrods, bright yellow flowers which attract large numbers of insects, particularly in autumn. It is often very hard even for a searching human to spot this spider on a yellow flower.^[9] These spiders are sometimes called 'banana spiders' because of their striking yellow color.^[10]

Females have light complexions, either white or yellow with darker sides. They may have some markings on the abdomen that can be brown or red. These markings are genetically determined and not affected by a background color change.^[11] Males are darker than females, with red or brown outer shells. They have a characteristic white spot in the middle that continues through the area around the eyes. Males specifically have two sets of red and white bands both dorsally and laterally.^[12][13] Similar species of the crab spiders appear in a variety of colors such as those of the genus Diaea, which can be lime green, or some species of Xysticus and Coriarchne which are brown.^[3]

Color change

Because of their photoreceptors, arthropods see the white form of the spider only as a dark shape against a dark background when it sits on pink flowers.

These spiders change color based on visual cues. The color-change is most obvious on females of this species. The ability of males and juveniles to change color has not been documented.^[3] Two other known spiders with this color change ability include Thomisus onustus and Thomisus spectabilis. Depending on the color of flower they see around them, they can secrete a liquid yellow pigment into the body's outer cell layer. The baseline color of the spider is white. In its white state, the yellow pigment is sequestered beneath the outer cell layer so that inner glands which are filled with white guanine are visible.^[14] They are able to match with greater accuracy to white flowers, such as Chaerophyllum temulum (the rough chervil) in particular, compared to yellow flowers based on the spectral reflectance functions.^[15] While the spider is residing on a white plant, it tends to excrete the yellow pigment instead of storing it in its glands. In order to change back to yellow, the spider must first produce enough of the yellow pigment. For this reason it takes these spiders much longer to turn from white to yellow than it does for them to go from yellow to white. The color change from white to yellow can take between 10 and 25 days while the opposite color change takes only about six days. The yellow pigments are kynurenine and 3-hydroxykynurenine.^[16] Color changes are induced by visual cues and spiders with impaired vision lose this ability.^[17]

Notably, spiders of this species sometimes choose to hunt on flowers that, to the human eye, they do not appear to match in color. For instance, they can be found hunting on the pink petals of the pasture rose (Rosa carolina). The spider appears white, or changes to white, causing it to stand out to human observers. Arthropods, on the other hand, serve as both predators and prey to Misumena vatia, and have photoreceptors that allow them to see ultraviolet, blue, and green light but oftentimes lack red receptors altogether. As a result, Misumena vatia is camouflaged, appearing dark on a dark background.^[3]

Sexual dimorphism

Misumena vatia is highly sexually dimorphic. Females are larger than males and tend to fall between 6–9 mm (0.24–0.35 in) in length. Males, on the other hand, are only 3–4 mm (0.12–0.16 in) long. The female's legs are white or yellow, while the male's first and second legs are brown or red and the third and fourth are yellow. Additionally, in concurrence with the male’s smaller size, the male Misumena vatia molts two fewer times than the female.^[3]

Female, imitating a flower

Other physical characteristics

Misumena vatia has two rows of eyes. Those in the anterior row are equally spaced and curved backward while those in the second row vary in appearance from animal to animal, and can be curved more or less than the first. The area around the eyes is narrower in the front than the back. The spider's hair is erect and can be either filiform or rod-shaped.^[18] The legs do not have spines, except under the tibia and metatarsal bones of the first two sets of legs. The appearance of the clypeus and the structure of the cephalothorax can be used to distinguish the genus Misumena within its subfamily.^[12][13]

Habitat and distribution

A misumena vatia in Germany

Misumena vatia is found only in North America and Europe. Other species of crab spiders, however, can be found all over the world.^[18] The species prefers a temperate climate and generally inhabits forest biomes.^[13] Misumena vatia is terrestrial and can be found on several plants and flowers such as milkweed and goldenrod in North America, as well as trillium, white fleabane (Erigeron strigosus),^[13] ox-eye daisy (Chrysanthemum leucanthemum), red clover (Trifolium pratense) and buttercups (Ranunculus acris)."^[19]

Home range

Females of this species do not travel more than a few yards (meters) from their feeding location. They are attracted by the fragrance of flowers, though other visual and tactile clues also help them choose a territory.^[5] Their survival depends on their ability to choose a small area home to flowering plants which will attract prey. Males are highly motile and may disperse great distances as they search for mates. Additionally, spiderlings may travel great distances by ballooning, if they find the area around their nest to be lacking in resources. However, this is risky as there is no guarantee that the search for a new territory will be successful.^[20]

Patch choice

Misumena vatia hunts large prey with a low rate of success. Hunting success rate is highly dependent upon the spider's choice of hunting site. Before they lay their eggs, females are heavy and slow, which necessitates that they choose a hunting site on which to stay. When hunting on their preferred plant of milkweed, they monitor nearby umbels to see if another site would be more profitable. Over the course of a few hours, Misumena vatia may recognize and move to another nearby hunting site. Most often, they move to flowers that produce more nectar and attract more prey, however occasionally some intentionally and consistently pick less profitable sites to hunt on. Thus, the population is dimorphic in terms of patch choice behavior. The reason a minority might choose poorer hunting sites on purpose remains unknown.^[3]

Diet

Hunting patterns

Misumena vatia with prey

Crab spiders are carnivorous, feeding on invertebrate insects such as flies, bees, butterflies, grasshoppers, dragonflies, and hoverflies.^[3][21] Bumblebees (Bombus appositus)^[22] provide the spider with the most biomass, but small syrphid flies (Toxomerus marginatus) are the prey captured most frequently. Other frequently captured prey include honeybees (Apis mellifera) and moths.^[21] Immature Misumena vatia commonly feed on smaller-sized prey such as thrips, aphids in the family Aphididae, and dance flies in the family Empididae. They may also use nectar and pollen as food sources when prey is scarce.^[20]

Misumena vatia is primarily dependent on its vision to hunt, so it typically finds and captures food during the day.^[23] Adult males search the upper stratum of field vegetation, where females are commonly found hunting, for potential mates. The spider can hunt bugs and insects larger than itself because it has the ability to use paralyzing venom to immobilize its prey. Misumena vatia waits, camouflaging itself on a flowering plant or on the ground, for prey to pass by, and then grabs the prey with its forelegs and quickly injects its venom. Unlike many spiders which wrap their prey in silk, Misumena vatia forgoes wrapping prey and instead allows its venom alone to subdue insects before eating them. It then uses its fangs to inject the immobilized prey with digestive enzymes before sucking out the rendered bodily liquids.^[18] This is a form of external digestion. As a result, prey size is not a limiting factor for consumption.^[20]

Although Misumena vatia most often hunts during the daytime, there is evidence that it is sometimes driven to hunt at night due to an increase in nocturnal prey activity. This behavior occurs most commonly in response to increased night-time activity by moths in early September.^[23]

Misumena vatia has the ability to retain its excretions for at least 50 days and will not excrete when confined to small spaces or near its hunting sites. Excretion may alert predators to the spider's whereabouts.^[24]

Diet-induced color change

Misumena vatia can also change color as a result of prey consumption. Once consumed, colorful prey can show through the thin, transparent epidermis of the abdomen, affecting opisthosomal coloration. Ingestion of red-eyed fruit flies cause the abdomen to turn pink. Coloration changes caused by prey consumption revert to the normal white or yellow within 4–6 days after prey ingestion. Color change intensity is positively correlated with the amount of colorful prey consumed. Color change intensity also decreases with the spider's age. These spiders have been observed to have pink, orange, yellow, brown, green, or white opisthosomas depending on the prey consumed.^[25]

Reproduction and lifecycle

Sex ratios among Misumena vatia vary from a ratio of 1.5 females per male at hatching to a ratio of 2.5–5.1 females per male by the time they reach adulthood. Since males must spend considerable time searching for females, they face danger from the environment, reducing their numbers. Males cannot mate multiple times in quick succession but require a two-day interval between matings.^[26] In nature, Misumena vatia produces a single brood. However, females are capable of producing another brood if artificially induced.^[27]

Nests

Female Misumena vatia prefer common milkweed (Asclepias syriaca) over spreading dogbane (Apocynum androsaemifolium), pasture rose (Rosa carolina), and chokecherry (Prunus virginiana) for nest construction. Females who lay eggs on milkweed have higher nesting success, which correlates with early survival of clutches.^[28] The nest appearance can vary widely, depending on the type of plant on which it is constructed. In the case of the pasture rose and the sensitive fern (Onoclea sinsibilis), nests consist of several small leaves bound together. These nests are more vulnerable to predators though, because they are not as tightly bound as those created on milkweed, and have a greater area that is covered only by silk.^[29][3]

Mate-guarding

A minority of males—only about ten percent—guard pre-reproductive females as they molt into their adult stage. Almost all males who guard such females mate with them after they have molted. The low level of mate guarding is related to the female-leaning sex ratio expressed by Misumena vatia. Males of this species tend to guard less frequently and exhibit less aggression than other closely related species, such as Misumenoides formosipes, which do not have a female-biased sex ratio.^[30]

Female on Achillea millefolium

Lifecycle

In May and early June, males molt into adulthood, with the number of adult males peaking between June 5 to July 15. Females do not molt into adulthood until mid to late June, with numbers of adult females peaking around June 25. After males molt, their body mass does not increase, remaining at about 4 mg (0.00014 oz). Males, however, do undergo body changes as they enter the adult stage. Their front legs lengthen while the abdomen shrinks.^[19] Females live an average of two years and spend most of this time guarding their eggs sacs and the territory (flowers) on which they hunt. Males have shorter lifespans by about a month.^[31] Only near the end of the female's second year of life will she allow males onto her territory to mate. Females lay their eggs most commonly in the middle of the summer; these hatch after 3.5 weeks.^[3] Females usually die very soon after their eggs have hatched, during their second winter.^[20] Young undergo one molt within the egg sac, and emerge after hatching as second instars. They can sustain themselves for a few days with the nutrients from their yolk sacs.^[3]

Mating

Mate-searching behavior

The much smaller males scamper from flower to flower in search of females and are often seen missing one or more of their legs. This may be due either to near misses by predators such as birds or to fighting with other males.^[32] Males exhibit a random pattern of searching for mates until they discover a female dragline.^[19] Females leave these draglines behind them as they search for prey. Males follow the draglines in search of potential mates. Unlike many spider species, the females do not deposit any pheromones on these lines. Males follow the lines mechanically rather than chemically. The tendency for a male to follow a line is highly influenced by its life stage and the stage of the female of interest. Adult males preferentially follow adult female and juvenile female draglines, while penultimate males do not display a specific preference. Male Misumena vatia are also more likely to follow lines laid by their own species than those of a related species.^[33]

Male–male interactions

Two males interested in the same female may compete, since encounters with females are relatively rare. This may include light touching, chasing, foreleg lashing, grappling, and biting between males. If the female is being guarded by an existing male, the guarding male may either fend off the challenger or be replaced. The male which finds the female of interest first has an advantage in any ensuing contest. In this species, unlike many other species of spider, older and younger males are generally the same size. While older males initiate contests more frequently than younger males, the nature of their attacks is less likely to include extensive bodily contact. Younger males win significantly more contests than older males. After a contest between males, the winner immediately mates with the female while the loser retreats.^[31]

Female–male interactions

When a male finds a female, he climbs over her head, over her opisthosoma and onto her underside, where he inserts his pedipalps to inseminate her.^[26] The male may wrap the female loosely with silk during copulation. Females have a pair of gonopores which the male pedipalp may enter for copulation. When the male inserts his pedipalp into the female's gonopore he will make rhythmic, vibratory movements that can last from 1–2 seconds. Gonopore contacts of less than 30 seconds will result in unfertilized eggs and a failed copulation.^[34] Matings last an average of four minutes.^[34]

Males can accurately identify the reproductive condition of potential mates. They prefer to mate with virgin females over those which have previously mated. Males mate for longer with virgin females and produce more pedipalp movements than during copulation with previously-mated females. Males are most likely to enter both gonopores of a virgin female, while they may only enter one gonopore of a previously-mated female. Females have a low probability of mating with a second male, but have a higher probability of mating with a second male than they do a third one.^[34]

The female then lays her eggs preferentially on plants from the Asclepias genus (milkweeds).^[22] When preparing to lay eggs, she first identifies a suitable location for her brood. She descends the plant stalk down to the leaf that she chooses and then rolls up the end of a leaf. She secures the leaf by spreading silk, creating a cocoon-like structure, and lays her eggs inside the nest she has created.^[20] She tends to lay her eggs at night.^[35] The young grow to be about 5 mm (0.20 in) by autumn and remain on the ground through winter. Their final molt, from penultimate instars to adults, occurs during May of the next year.^[36]

Because Misumena vatia employs camouflaging, it can focus more energy on growth and reproduction rather than on finding food and escaping from predators. As in many Thomisidae species, there is a positive correlation between female weight and egg clutch size, or fecundity.^[37] Selection for larger female body size thus increases reproductive success.^[38]

Sperm quantity

This species exhibits a high first-male sperm precedence, so providing a virgin female with a large sperm quantity is advantageous. Because there is a very limited number of virgin females available at any given time, there is strong selective pressure that favors males that provide large sperm quantities. The need to produce a large sperm quantity for each copulation prevents males from remating quickly. Additionally, females are likely to deny subsequent males after their first mating as further reproduction will interfere too strongly with the female's foraging success. More matings are also unfavorable because they can increase the risk of infection with sexually transmitted parasites or diseases.^[34]

In some cases, males can tell whether a female has mated previously from a distance. This may be due the female's heightened aggression that manifests after she has mated once. It is more common, however, that in order to assess the reproductive history of a given female, the male must first mount her, which is dangerous for the male as there is a chance the female may attack, capture, and kill him. Since females are difficult to locate and the cost of searching for them is so high, the risk is usually worthwhile to the male. In addition, since locating females is difficult, there is a low chance that another male has previously inseminated a given female, so it is therefore beneficial for males to provide large quantities of sperm. This adaptation is also beneficial in the case that a female loses her first brood. When a female has been inseminated with a large quantity of sperm, she may have enough to fertilize a second brood to replace the lost first brood.^[34]

Preying on Trigona fulviventris

Sexual cannibalism

Like many other arachnids and insects, Misumena vatia may express sexual cannibalism; however it is only considered moderately common. In cases of precopulatory sexual cannibalism, older males are more likely than younger males to be targets of attack, and are more likely to suffer death or injury as a result of such an attack, especially during the latter half of the mating season. This could be a result of a decreased ability among older males to evade attack from females. Older males do not tend to display riskier mating behavior than younger males. The size of the male does not influence its likelihood of being cannibalized during copulation. Females increase cannibalistic attacks as the mating season progresses. More males tend to be cannibalized after mid July, which could be a result of male aging but is more likely a result of increased female aggression during this time.^[39] Non-reproductive cannibalism is uncommon among Misumena vatia. However, it has been observed in individuals in roughly one percent of broods. In these broods, cannibalism tends to occur among spiderlings. Cannibalistic individuals can be up to three times larger than those who are non-cannibalistic.^[40]

Parental care

Egg-guarding

Like many other species, Misumena vatia guards its nest to protect its vulnerable eggs from attack. Nest guarding increases the spider's overall reproductive success by protecting against predation from ichneumonid and dipteran egg predators. These spiders are usually observed guarding the nest by standing on its underside, the most vulnerable face of the nest. Most guarding spiders will remain by the nest until the young have begun to emerge from their eggs—about three weeks. A minority of spiders abandon their nests before spiderlings have hatched, while some may remain until all the young have hatched or longer. Most die within a few days of the hatching of their young.^[35]

Enemies

Parasitization by the ichneumonid wasp, Trychosis cyperia, an egg predator, is common.^[28] The wasp deposits an egg in the nest and its larva feeds on the eggs. One attack can destroy the nest completely. Misumena vatia experience strong selection to minimize attack from wasps, which is why egg guarding by the female is important for reproductive success. Wasps tend to feed on small egg masses guarded by small spiders, as small spiders cannot defend their nests as effectively.^[35] Other known predators include ants, other spiders, birds, lizards, and shrews.^[41] When defending the nest from an approaching predator, females typically raise their front legs in a display otherwise observed when they are attacking prey.^[35]

Physiology

Sensation

These spiders respond quickly to motion that is both within and outside of their visual range. To do so, they rely heavily on several types of mechanoreceptors. Tactile hairs sense touch, trichobothria sense air currents, and slit sensilla are sensitive to vibrations and mechanical stresses. While still important, vision plays a less important role in prey detection. Remarkably, Misumena vatia fail to notice prey when it is stationary.^[3]

Vision

Close-up showing eyes

These spiders have two rows of four eyes each for a total of eight eyes. The antero-lateral (75 μm diameter) and postero-lateral (65 μm diameter) eyes are the larger in size of the four sets of eyes. The antero-median (59 μm diameter) are considered the principal eyes and along with the postero-median (55 μm diameter) constitute the smaller of the sets. All of the eyes other than the principal eyes are considered the secondary eyes. The antero-median eyes appear the clearest, while the other sets of eyes appear darker. The postero-median eyes look directly upward, and their field of view overlaps somewhat with that of the postero-lateral eyes. The antero-lateral and postero-lateral eyes also share a slight overlap in their visual fields. The antero-lateral eyes give these spiders a region of binocular vision. The organization of the antero-lateral, postero-median, and postero-lateral eyes allows these spiders to see nearly their entire upper visual environment.^[17]

The four pairs of eyes are similar in structure, all containing a retina, a dioptric apparatus, and a cellular vitreous body. The outermost layer of the eye is the lens. The columnar cells of the vitreous body stand between the lens and the retina, and their nuclei rest next to the retina. Three layers of pigment cells surround the vitreous body. The epidermis is the outer layer, and it contains electron-dense granules and electron-lucent inclusions of micro-crystals.^[17] The middle layer contains dark, pigment granules, and the innermost layer contains larger, dark, pigment granules inside glial cells. These layers prevent light that may enter through a nearby transparent cuticle from reaching the retina, keeping each eye isolated. The retina contains photoreceptor cells and other supporting cells.^[17]

The principle eyes have a complex and unique organization. They have three different photoreceptive segments. The periphery contains a half-circle of one type of rhabdomere, while the center is pigmented and contains two types of rhabdomeres. These spiders also have a "giant rhabdom" in the lowest layer of the center of the retina. Only the light entering along its optic axis stimulates this giant rhabdom, so the visual information comes in the shape of a dot. Misumena vatia can control the trajectory of the giant rhabdom by moving their eye muscles, which means these single points of visual information are integrated to generate the spider's visual field.^[17]

Vision plays an important role in the spider's substrate color matching. Misumena vatia have the necessary physiological machinery to see color, and are most sensitive to wavelengths of light between 340-520 nm. Misumena vatia's principle eyes have tiered retinas, with four layers containing different types of photoreceptors. These spiders have been proven to have green and UV photoreceptors, and likely have many other types which allow them to see a full range of colors. The secondary eyes are dichromal, meaning that they have two types of photoreceptors. Since Misumena vatia use their visual systems to inform color changes, they must be able to see color in their environment and on their own bodies. The visual field of the antero-lateral and antero-medial eyes allow the spider to see its legs, while the postero-lateral eyes see the opisthoma. Since the visual fields are so wide, these spiders see their own bodies and the color of their surroundings, which supports the idea that color matching is facilitated by the visual system.^[17]

Autotomy

Autotomy, the loss of one leg, can happen in a variety of critical situations, including fleeing from predators, fighting, and getting rid of parasites. The disadvantage is obvious, but most spiders can grow back lost limbs if the loss occurs during a juvenile stage and before the final molting.^[42]

The loss of an anterior leg is common among males. Over their lifetimes, approximately 30 percent of males will lose one of their anterior legs. One direct disadvantage of losing a leg is a decrease in mobility. Spiders with all eight legs have considerably higher body weights, showing that losing legs negatively impacts foraging and significantly decreases the speed with which they can move along lines.^[42] Since females are widely dispersed, the impairment of mobility adversely affects the male’s reproductive success.^[42]

References

Misumena vatia es una araña cangrejo (familia Thomisidae) bastante común en el holártico: Eurasia y América del Norte. El macho mide entre 4 y 5 mm mientras que la hembra alcanza 10 mm. Esta especie fue descrita por el aracnólogo sueco Carl Alexander Clerck en 1757. El nombre del género Misumena proviene de las palabras en griego “misoúmenus” que significa odiado. El nombre específico vatia proviene del latín que significa doblado hacia afuera.^[1]​^[2]​

Descripción

La hembra mide de 8 a 12 mm de largo total. El carapacho es blanco amarillento con una banda longitudinal y rayas saliendo de los lados de la región del prosoma; clípeo de color blanco; región de los ocelos rojizos, forma de disco con pelos fuertes, región de la cabeza con setas; ocelos no muy desarrollados; ocelos laterales, posteriores y anteriores sobre el tubérculo ocular; surco medial y surco cervical fusionados y diferenciados, surcos radiales visibles; quelíceros amarillo claro; endito, labium y esternón de amarillo claro a marrón amarillento; patas amarillo claro con 5 a 6 pares de espinas en la parte ventral del metatarso de las patas I y II; pedipalpo verde amarillento; abdomen blanco amarillento con setas cortas y robustas; sin patrón distinto en el dorso; parte posterior redondeada y más ancha; tres pares de impresiones musculares distintas; con coloración variable entre blanco, amarillo y verde claro, algunas veces con rayas rojizas del lado dorsoventral; epiginio con capucha central presente, espermateca globular. Macho con un largo total de 2,5 a 4 mm. La coloración del cuerpo es más obscura que en las hembras; carapacho marrón amarillento con márgenes oscuros; abdomen marrón grisáceo y alargado con forma ovoide; pedipalpo del macho con la tibia con apófisis ventral, retrolateral e intermedia.^[3]​

Misumena vatia

Misumena vatia hembra

Distribución

Corea, China, Japón, Rusia, Mongolia, Europa, América del Norte.^[3]​

Hábitat

Frecuentemente asociada con Solidago, que atrae muchos insectos a los que caza y devora. Vive en las flores, especialmente las de color blanco y amarillo. El macho es algo más oscuro que la hembra, aunque la especie es de un color muy variable, blanco, crema, amarillo, verde o con manchas y bandas de color según la flor en la cual caza (homocromía).^[3]​

Estado de conservación

No se encuentra dentro de ninguna categoría de riesgo en las normas nacionales o internacionales.

Referencias

• World Spider Catalog (2016). The world spider catalog, version 17.5 Natural History Museum Bern, Misumena vatia. Acceso: 22 de noviembre de 2016.

Kukkahämähäkki (Misumena vatia) on yleinen ja melko kookas rapuhämähäkkeihin lukeutuva hämähäkkilaji.

Koko ja ulkonäkö

Kukkahämähäkin naaras on kookas, 9–11 mm pitkä. Koiras huomattavasti pienempi, vain 3–4 mm:n pituinen. Naaras on lähes yksivärinen, vain takaruumiin sivuilla saattaa olla punaiset juovat tai täplät. Erikoisena piirteenä aikuinen naaras kykenee vaihtamaan väriään keltaisesta valkoiseen ympäristönsä mukaan. Myös vihertävänsävyisiä yksilöitä tavataan ja nuoret kukkahämähäkit ovat vihreitä. Hämähäkin värin vaihtumiseen kuluu pari vuorokautta. Koiraan eturuumis ja etummaiset raajat ovat laajalti tummanruskeat ja takaruumiin selkäpuolella on kaksi punaruskeaa pitkittäisjuovaa. Muilta osin koiras on kellertävä tai valkoinen. Kaksi etummaista raajaparia ovat huomattavasti taaempia raajoja pitemmät ja väijyvä hämähäkki pitää niitä leveälti ojennettuna ruumiin sivuilla.^[1][2][3]

Levinneisyys

Laajalti levinnyt laji, jota tavataan suurimmassa osassa Eurooppaa, Aasian pohjoisosissa sekä Pohjois-Amerikassa. Suomessa sitä tavataan ainakin eteläiseen Lappiin saakka, mutta laji on selvästi yleisempi maan eteläosissa.^[2][4]

Elintavat

Kukkahämähäkit elävät niityillä, kedoilla, tienpientareilla ja muilla avoimilla paikolla. Heimolleen tyypilliseen tapaan se ei kudo pyyntiverkkoa vaan saalistaa väijymällä. Hämähäkki istuu kukassa suojavärinsä turvin ja odottaa kukkaan lentävää hyönteistä. Tavallisimmin hämähäkin tapaa valkoisesta tai keltaisesta kukasta, mutta sen havaitseminen on vaikeaa, ellei hämähäkin väri satu poikkeamaan kukan väristä. Kukkahämähäkit parittelevat alkukesällä ja naaras munii munat seitistä tekemäänsä munakoteloon, jonka se piilottaa kasvien lehtien väliin. Poikaset talvehtivat karikkeen joukossa ja aikuistuvat seuraavana keväänä.^[2]

Hämähäkin värinmuutoksen mahdollistava kemia on monimutkaista, eikä mekanismia tunneta kovin hyvin.^[5]

Lähteet

Aiheesta muualla

• BugGuide.net (englanniksi)
• UK Safari (englanniksi)

Misumena vatia, la Thomise variable, est une espèce d'araignées aranéomorphes de la famille des Thomisidae^[1].

Elle est aussi appelée araignée-crabe en français^[2],[3].

Distribution

Cette espèce se rencontre en zone holarctique^[1].

Description

Les mâles mesurent de 3 à 5 mm et les femelles de 7 à 11,5 mm^[4].

L'abdomen va en s'élargissant vers l'arrière, et reste plus ou moins arrondi postérieurement. Chez la femelle le céphalothorax est blanc ou jaune avec une large bande brun-jaune de chaque côté et l'abdomen blanc, jaune ou vert très pâle avec de façon inconstante dans la moitié antérieure deux bandes longitudinales rouges. Par homochromie, la couleur de la femelle peut varier entre le jaune et le blanc, voire vert pâle, suivant la fleur sur laquelle elle chasse.

Chez le mâle le céphalothorax est brun-rouge ou noir avec une large bande jaunâtre dans la partie céphalique et l'abdomen blanc mat, orné de deux lignes parallèles bordées de noir^[5].

Les deux premières paires de pattes sont plus longues ; elles marchent sur le côté comme les crabes^[6].

• Une femelle sur fond blanc

• Femelle sur fond multicolore

• Une femelle sur fond jaune

• Femelle de face

• Un mâle, beaucoup plus petit

• Un mâle aux pédipalpes renflés

• Une misumena vatia se restaurant d'un insecte sur une fleur.

L'homochromie adaptative est connue chez les araignées dans deux cas : les Misumena et les Thomisus^[5]. Le changement de couleur est rendu possible en 24 heures par la sécrétion d'un pigment liquide jaune composé de kynurénine et de 3-hydroxykynurenine dans les couches de cellules extérieures du corps^[7]. Lorsque l'araignée est sur un fond blanc, ce pigment est transporté dans les couches profondes laissant apparaître les glandes de guanine blanche^[8].

Si l'araignée séjourne longuement sur une plante blanche, le pigment jaune est souvent excrété. Pour repasser au jaune, il faudra donc que l'araignée prenne le temps de sécréter à nouveau ce pigment^[9].

Éthologie

Mâle sur l'abdomen d'une femelle qui mange un Bourdon des champs.

Femelle imitant une fleur

Les adultes sont visibles de mai à juillet.

Les mâles, beaucoup plus petits que les femelles, parcourent les fleurs à la recherche de femelles et sont souvent vus avec une ou plusieurs pattes en moins, probablement du fait d'attaques de prédateurs ou d'autres mâles en compétition. Quand un mâle trouve une femelle, il grimpe sur son céphalothorax à la recherche de son orifice sexuel, où il insère son pédipalpe pour l'inséminer.

Les juvéniles atteignent une taille de 5 mm à la fin de l'automne et hivernent sur le sol. Ils muent une dernière fois au mois de mai de l'année suivante.

Misumena vatia se tient tapie sur les fleurs pour se précipiter sur les proies. Elle est fréquemment associée au Solidago qui lui sert de support à la chasse à l'affût, et qui a l'avantage d'attirer beaucoup d'insectes^[10].

Systématique et taxinomie

Cette espèce a été décrite sous le protonyme Araneus vatius par le naturaliste suédois Carl Alexander Clerck en 1757^[11].

Cette espèce admet de nombreux synonymes^[1] :

Publication originale

• Clerck, 1757 Svenska spindlar, uti sina hufvud-slågter indelte samt under några och sextio särskildte arter beskrefne och med illuminerade figurer uplyste. Stockholmiae, p. 1-154.

Notes et références

Misumena vatia Clerck, 1757 è una specie di ragno della famiglia thomisidae^[1]. Esso viene comunemente chiamato ragno granchio.

Distribuzione e habitat

Misumena vatia è diffuso in nord America ed Europa. Predilige un clima temperato. Vive tra la vegetazione ed è solito posizionarsi sui fiori^[1]. è comunemente presente in Italia, comprese le isole maggiori^[2].

Descrizione

Vista ravvicinata di misumena vatia. Si notano le zampe anteriore più grosse rispetto alle posteriori, le due file di occhi e i piccoli cheliceri.

M. vatia deve il suo nome comune alla sua somiglianza con un granchio. Il suo corpo è infatti corto, largo e schiacciato e le prime due paia di zampe, più larghe delle altre, vengono tenute divaricate, facendo assomigliare il suo aspetto e la sua postura a quelli di un granchio. Questa specie presenta dimorfismo sessuale, ed infatti le femmine sono più grandi dei maschi e variano per colorazione e disegni. Le femmine sono lunghe dai 6 ai 9mm, mentre i maschi dai 3 ai 4mm. Le femmine hanno una colorazione chiara: le zampe e la parte superiore del corpo sono bianchi o gialli, con aree più scure e dei segni rossastri sull'addome. I maschi sono più scuri, ed infatti il corpo è rosso o marrone rossastro, con punti bianchi che partono dall'area degli occhi e si estendono nella parte centrale del dorso. Le prime due paia di zampe sono marroni rossastre, mentre le ultime due gialle. i maschi hanno inoltre due paia di bande, dorsali e laterali parallele, rosse. i cheliceri sono piccoli e sottili. possiede due file di occhi. La fila anteriore è leggermente ricurva con occhi equidistanti. la fila posteriore può essere più o meno ricurva, con occhi equidistanti^[1].

Misumena vatia cattura una vespa

Biologia

Riproduzione e crescita

Le femmine depongono delle uova che proteggono con la loro seta. I piccoli che nascono hanno già l'aspetto generale identico a quello di un adulto, salvo per le ridotte dimensioni. Come tutti i ragni, compiono delle mute durante la crescita, per liberarsi dell'esoscheletro, troppo piccolo per ospitarli ancora^[1].

Locomozione, dieta e predazione

Al pari di molte specie di Tomisidi, sono ragni cacciatori; essi, infatti non costruiscono la tela, ma tendono agguati sulle piante e sui fiori, sfruttando l'omocromia dei loro colori con il luogo dove decidono di nascondersi, (che sia un fiore, una foglia o un oggetto), per mimetizzarsi. Questa abilità è possibile grazie alla variazione nella distribuzione dei pigmenti del corpo, che avviene in pochi giorni dopo essersi stanziati nel luogo di caccia. Quando una preda capita loro a tiro, la afferrano con le prime due paia di zampe e le iniettano il veleno attraverso i cheliceri per immobilizzarla. Non avvolgono la preda nella seta prima di mangiarla. Si nutrono di invertebrati, come mosche, farfalle e cavallette. Attaccano abitualmente prede grandi e temibili come le api e le vespe, e sono regolatori naturali delle popolazioni di insetti. Essi sono in grado di muoversi abilmente sia in avanti che lateralmente e all'indietro^[1][2].

Veleno

Il suo morso è innocuo per i vertebrati, essendo il veleno debole e i cheliceri piccoli^[1].

Predatori

Può essere predato da: vespe, formiche, altri ragni, lucertole, uccelli e roditori carnivori, come i toporagni^[1].

Un esemplare femmina di misumena vatia

Note

Geltonasis žiedvoris (lot. Misumena vatia; vok. Veränderliche Krabbenspinne, Gelbe Krabbenspinne) – krabvorių šeimos gentis.

Vorų dydis: patelė 9,0-11,0 mm, patinėlis – 3,0-4,0 mm. Šoninės akys yra ant mažų apvalių pakilimų, užpakalinės eilės akys viena nuo kitos išsidėsčiusios vienodu atstumu. Pilvelis apvalus.

Lytiškai subrendusių patelių spalva labai varijuoja: ant geltonų žiedų aptinkami vorai su geltonu pilveliu, ant baltų žiedų – su baltu, ant dobilų – su raudona dėme ant pilvelio. Spalvų įvairovė tokia didelė, kad kai kurie autoriai šiuos spalvinius variantus laikė atskiromis rūšimis. Šis persidažymas vyksta negreitai, o trunka apie 3 dienas (vorų mimikrija).

Patinėlio galvakrūtinė tamsiai ruda, su šviesia medialine juosta. Pilvelis šviesiai rudas, su tamsiais kraštais ir dviem tamsiomis medialinėmis linijomis. Kojos šviesios, su tamsiai rudais žiedeliais.

Geltonasis žiedvoris užpuola bites ir vapsvas, kurias paralyžuoja įkąsdamas į sprandą ir voratinklinėmis gijomis pritvirtina po žiedu. Po to iščiulpia taip, kad lieka tik tuščias kiautas.

Lytiškai subrendę individai aptinkami V-IX mėn. Kiaušinėlius deda 2 kartus. Rudenį jaunikliai skraido voratinkliais.

Dažniausiai sutinkamas žolėje, ant žydinčių augalų, tačiau dėl prisitaikėliškos spalvos yra beveik nematomas.

• Geltonasis žiedvoris

• Geltonasis žiedvoris ♀
• Geltonasis žiedvoris užpuolęs drugį

• Geltonasis žiedvoris užpuolęs musę

• Misumena Vatia

Vikiteka

De gewone kameleonspin (Misumena vatia) is een goed gecamoufleerde spin uit de familie der krabspinnen.

Kenmerken

Kameleonspinnen hebben, zoals de meeste krabspinnen, een relatief klein kopborststuk en een groot, haast bolvormig achterlijf. De vrouwtjes kunnen 10 mm lang worden, terwijl de mannetjes niet langer dan 5 mm worden. Jonge mannetjes kunnen vroeg in de zomer vrij klein en moeilijk te ontdekken zijn. Kameleonspinnen zijn geel of wit, afhankelijk van de kleur van de bloem waarin ze zich ophouden. Dankzij deze camouflage kunnen ze hun prooien verrassen.

Leefwijze

Kameleonspinnen maken geen web, maar verschuilen zich in bloemen, waar ze bezoekende insecten bij verrassing grijpen en leegzuigen. De leeggezogen prooi blijft soms aan de bloem hangen, wat de aanwezigheid van de spin kan verraden.

Verspreiding en leefgebied

De spin komt overal op het noordelijk halfrond voor. In Noord-Amerika komt de spin veel voor op guldenroede (Solidago sp.). Deze heeft heldergele bloemen die veel insecten aantrekken, vooral in de herfst.

Voortplanting

De oudere vrouwtjes hebben grote hoeveelheden naar verhouding grote prooien nodig om goed ontwikkelde eieren af te kunnen zetten. De mannetjes draven van bloem tot bloem op zoek naar de veel grotere vrouwtjes. Vaak missen ze een of twee van hun poten. Dit kan komen door roofdieren, zoals vogels, of door gevechten met andere mannetjes. Als een mannetje een vrouwtje heeft gevonden, klimt hij over haar kopborststuk naar haar achterlijf, waar hij zijn pedipalpen in de geslachtsopening van het vrouwtje steekt om zijn sperma af te zetten. De jonge spinnen zijn in de herfst meestal ongeveer 5 mm lang en brengen de winter op de bodem door. In mei van het volgende jaar vervellen ze voor de laatste keer.

Kleurverandering

Kameleonspinnen kunnen in kleur variëren tussen wit en geel, vandaar hun naam. De kleurverandering wordt mogelijk veroorzaakt door een vloeibaar geel pigment in de buitenste cellaag van het lichaam. In een witte omgeving wordt het gele pigment naar diepere cellagen verplaatst, zodat de binnenste laag, die gevuld is met het witte guanine, zichtbaar wordt. Als de spin lang in een witte omgeving verblijft, wordt het gele pigment op een bepaald moment afgebroken. Het zal de spin daarna relatief veel tijd kosten om weer geel te kleuren, omdat het pigment dan opnieuw aangemaakt moet worden. De kleurverandering van wit naar geel duurt dan 10 tot 25 dagen, terwijl van geel naar wit maar 6 dagen duurt. De gele pigmenten staan bekend als kynurenine en 3-hydroxykynurenine.

Afbeeldingen

• Vrouwtje

• Mannetje

• Mannetje

• Vrouwtje in witte fase

• Vrouwtje dat een bloem imiteert

• subadult mannetje

Zie ook

• Krabspinnen

Externe links

• (en) Foto's van de gewone kameleonspin
• (en) Nog meer foto's

• Dit artikel of een eerdere versie ervan is (gedeeltelijk) vertaald vanaf de Engelstalige Wikipedia, die onder de licentie Creative Commons Naamsvermelding/Gelijk delen valt. Zie de bewerkingsgeschiedenis aldaar.
  

Misumena vatia er en av edderkoppene i gruppen krabbeedderkopper (Thomisidae). De er predatore og jakter på mindre dyr. Vanligvis sitter de stille og venter på byttedyret. Navnet krabbeedderkopper, har de fått på grunn av sin sidelangs gange, ved en sammenligning med krabber.

Utbredelse

Misumena vatia er ganske vanlig og er utbredt i holarktis. Den finnes i Norge.

Utseende

Som voksne (imago) er hunnen mellom 7 og 10 mm, mens hannen er mellom 3 og 5 mm lange (kroppens lengde). Hunnen er fargevariabel, vanligvis gul eller litt gulgrønn, men kan være mørkere eller nesten helt hvit. Hun kan ha rødlige fargeflekker, men disse kan mangle. Hannene er mer kontrastrikt farget i gult og mørk brunsvart.

De har en kompakt todelt kropp, bakkroppen og forkroppen «overlapper» hverandre. Forkroppen er bred og flat sett ovenfra. Foran på hodet er det åtte øyne. Beina er kraftige og korte. Hos alle krabbeedderkopper er de to fremste beina lengre enn de to bakerste beina.

Misumena vatia er den eneste norske arten fra slekten Misumena, så forveksling med andre arter skulle ikke by på et problem. Flere av artene i slekten Misumena er ganske lik hverandre. For sikker artsbestemmelse kreves ofte nærmere undersøkelse av de kjønnsmodne edderkoppens genitalier, hos hunner epigynet og hos hanner pedipalpenes siste ledd.

Bildegalleri

• Hannen er mindre enn hunnen og mer kontrastrikt farget.

  Foto: James K. Lindsey
• Ett lyst eksemplar

  Foto: James K. Lindsey
• Med en honningbie, (Apis mellifera)

  Foto: Michael Apel
• Med røde flekker på bakkroppen. byttet er en blomsterflue

• Klart gult farget.

  Foto: D. Gordon E. Robertson
• En hunn i venteposisjon for et passende bytte

Litteratur

• W. Nentwig, A. Hänggi, C. Kropf & T. Blick (Hrsg.): Spinnen Mitteleuropas – Bestimmungsschlüssel, slekten (gattung) Misumena (tysk)
• Bergersen, Ove. 1981. Forsidedyret. (Krabbeedderkopper). Insekt-Nytt 6 (4) side 6-7
• Aakra, Kjetil. 2004. En innføring i edderkoppenes verden. Insekt-Nytt 29 (1/2) side 43

Eksterne lenker

• (sv) Misumena vatia hos Dyntaxa
• (en) Misumena vatia i Encyclopedia of Life
• (en) Misumena vatia i Global Biodiversity Information Facility
• (en) Misumena vatia hos Fauna Europaea
• (en) Misumena vatia hos NCBI
• (en) Misumena vatia hos ITIS
• (en) Kategori:Misumena vatia – bilder, video eller lyd på Wikimedia Commons
• (en) Misumena vatia – galleri av bilder, video eller lyd på Wikimedia Commons
• Misumena vatia – detaljert informasjon på Wikispecies
• Misumena vatia - europspiders.com (flotte bilder)
• Krabbeedderkopper – edderkopper.net (norsk)

Samiec

Samica

Misumena vatia

Kwietnik (Misumena vatia) – gatunek pająka z rodzaju Misumena, liczącego około 40 gatunków. Nazwa rodzajowa pochodzi od greckiego słowa misúmenos - znienawidzony.

Występowanie

Jest szeroko rozprzestrzeniony. Występuje w Europie od Morza Śródziemnego aż po Skandynawię, w Azji i Ameryce Północnej. W Polsce jest dość pospolity.

Środowisko

Występuje na otwartych terenach: pola uprawne, łąki, bagna, ogrody, obrzeża lasów i ścieżek. Spotkać go można głównie od maja do lipca.

Morfologia

Długość ciała samicy 7–10 mm, samca 3–5 mm. Ma ukośnie, podobnie jak krab rozstawione odnóża, przednie są dłuższe od tylnych. Na głowotułowiu cztery pary oczu; dwie z przodu, dwie po bokach wzgórka ocznego. Charakteryzuje go zdolność do zmiany ubarwienia – ubarwienie dostosowuje do miejsca, w którym przebywa, a także do rodzaju owadów, na które poluje. Może to być ubarwienie białe, żółte lub brązowawe, w różnych odcieniach. Zmiana ubarwienia zajmuje od 6 do 25 dni. Dodatkowo na odwłoku posiada czasami czerwone pasy. Jest to tzw. ubarwienie ochronne, ułatwiające mu kamuflaż. Zdolność do zmiany ubarwienia mają tylko samice, proces ten jest stopniowy. Samiec ma ciemne przednie odnóża i brązowy głowotułów, a odwłok żółty z ciemnym wzorem. Młode kwietniki są przeważnie zielone.

Tryb życia

Nie buduje sieci, a wytworzoną nić wykorzystuje jako narzędzie do szybkiego przemieszczania się. Na swoje ofiary czatuje najczęściej na kwiatach. Można go spotkać także na liściach drzew. Tylnymi odnóżami przytrzymuje się podłoża, przednie trzyma szeroko rozłożone. Po błyskawicznym ataku na kompletnie zaskoczone ofiary wstrzykuje im jad i soki trawienne. Spożywa je na miejscu, wysysając rozpuszczone przez soki trawienne wnętrzności, tak że pozostaje tylko chitynowy oskórek. Skutecznie atakuje różne owady, w tym jadowite pszczoły i osy.

Rozmnażanie

Kopulacja odbywa się wiosną i wczesnym latem. Podczas kopulacji samiec przez pewien czas zwisa z odwłoka samicy. Samica składa jaja w kokonie jajowym pomiędzy liśćmi, które łączy z sobą nicią. Młode pająki zimują w ściółce i wychodzą z niej na wiosnę.

Gatunki podobne

Thomisus onustus – różni się dwoma garbkami na odwłoku. Wykazuje też większą zmienność ubarwienia – od białego do fioletowego. Młode kwietniki natomiast można łatwo pomylić z wieloma innymi, podobnymi gatunkami o zielonym ubarwieniu.

Ciekawostki

• Został wybrany europejskim pająkiem roku 2006 przez The European Society of Arachnology.

Bibliografia

• H. Bellman.: Pająki – najważniejsze gatunki krajowe. Przewodnik kieszonkowy. Warszawa: MULTICO Oficyna Wydawnicza, 1999, s. 96.
• Heiko Bellmann: Owady. Dodatkowo najważniejsze pajęczaki. MULTICO Oficyna Wydawnicza, s. 424. ISBN 978-83-7073-418-3.
• I. Mikulska: Poznaj pająki. Warszawa: PZWS, 1960, s. 65.

Linki zewnętrzne

• European Spider of the Year 2006 (tłumaczenie na jęz. pol.)

Ubarwienie ochronne stosowane przez samicę kwietnika

Kwietnik na białym powoju polnym

Kwietnik potrafi przybrać odpowiednią barwę ochronną

Kwietnik dostosował się do kwiatów ostu

Biały kwietnik na białych kwiatach staje się niewidoczny

Technika polowania kwietnika

(godz. 13:59) Kwietnik rozpoczyna polowanie na muchówkę

(godz. 14:00) Pająk chwyta muchówkę i wstrzykuje jej jad

(godz. 14:03) Kwietnik przytrzymuje upolowanego owada za głowę

(godz. 14:09) Pająk kwietnik rozpoczyna wysysanie ofiary

(godz. 14:48) Pająk porzuca owada, z którego pozostał tylko chitynowy oskórek

Misumena vatia, conhecida pelo nome comum de aranha-caranguejo-das-flores,^[1] ou aranha-caranguejeira é uma aranha da família Thomisidae existente na Europa e na América do Norte. Os dois pares de patas dianteiros são maiores que as restantes, e são mantidos abertos para apanhar presas. O tamanho das patas e a forma do corpo achatada e larga fazem com que seja fisicamente parecido com caranguejos, daí o seu nome comum de Aranha-Caranguejo.

Esta aranha é, tal como as restantes espécies desta família, um predador de espera. Adopta uma estratégia em que, camuflada^[2][3] espera a passagem dos insectos voadores que procuram néctar entre as pétalas das flores. Com as patas posteriores segura-se firmemente, enquanto que com as patas anteriores, que são muito mais fortes e projectadas para fora, agarra os visitantes da flor com uma velocidade surpreendente. Ao mesmo tempo que captura a presa, administra uma dentada venenosa. Para se alimentar a aranha suga a presa por pequenos buracos, de tal forma que é deixado um exosqueleto quase completo sobre a flor.

Habitat:

Esta espécie é geralmente encontrada em zonas de espaços abertos como prados, charnecas e campos agrícolas, mas também ocorre noutros locais onde haja muita exposição solar, como nos caminhos, nas fronteiras florestais, nos terrenos baldios e nos jardins. Na Europa a Misumena ocorre da Escandinávia ao Mediterrâneo. Também pode ser encontrada no Nordeste Asiático e na América do Norte. Ocorre em Portugal e toda a Península Ibérica. No Reino Unido a espécie parece ocorrer apenas na região Sul.^[4]

Referências

Misumena vatia este o specie de păianjen din familia Thomisidae. El mai este supranumit și păianjen floare, deoarece vânează insecte ascunzând-se în flori, de regulă albe sau galbene.

Descriere

Masculul este, relativ, foarte mic, ajungând până la 5 mm lungime. Femela poate crește până la lungimea de 10 mm (fără dimensiunile picioarelor). Acest păianjen poate fi galben sau alb, în dependență de culoarea flori pe care vânează. Femela tânîră preferă să-și aștepte prada pe florile de margarete, floarea soarelui sau la speciile de Solidago. Ea ușor își schimbă culoarea. Femela maturizată necesită cantități mari de pradă pentru a depune ouăle. Colorația oferă un bun camuflaj, de aceea insectele nu observă păianjenul pe flloare și ușor sunt prinse de acesta. Chiar și omului îi este dificil să recunoască păianjenul pe floare. Picioarele anterioare sunt foarte lungi. Lungimea lor permite păianjenului să țină albina la distanță,astfel că acul să nu ajungă la păianjen.

Schimbarea culorii

Schimbarea culorii păianjenului are loc datorită secreției unor pigmenți lichid de culoare galbenă, în stratul externe de celule ale tegumentului. Pigmenți galben au fost identificați ca kynurenină și 3-hydroxykynurenine^[1], iar cel alb reprezintă guanina. Guanină este pigmentul stabil și mereu prezent în tegumentul corpului și în dependență de prezența sau lipsa celui pigmenților galbeni se stabilește culoarea păianjenului. Schimba culoarea este indusă de un feedback vizual. Când păianjenul locuiște pe o floare galbenă atunci celulele epiteliale excretă pigmenții galbeni. Din cauza dominării culorii galbene, culoarea guaninei nu se vede, păiajenul căpătând nuanța respectivă.
Schimbarea culorii de la alb la galben durează 10 - 25 de zile, invers aproximativ 6 zile.

Reproducere

Masculul mic aleargă din floare în floare în căutare de femelei. Adesea sunt vazuți cu un picior sau mai mulți despicați. Acest lucru poate rezultă din lupta cu alți păianjeni sau evadarea de la dușmani, cum ar fi păsările.
Până la sfârșitul anului, juvenilii ating lungimea de 5 mm, iernează în sol sau printre resturile de vegtație. Ei năpârlesc pentru prima dată în luna mai anului viitor.

Referințe

Legături externe

Wikimedia Commons conține materiale multimedia legate de Misumena vatia

Wikispecies conține informații legate de Misumena vatia

• Pictures of M. vatia on BugGuide.net
• Pictures of M. vatia (free for noncommercial use) (another one)
• Goldenrod crab spider Wildlife Goldenrod crab spider

Araneus vatius
Aranea calycina
Aranea 4-lineata
Aranea kleinii
Aranea osbekii
Aranea hasselquistii
Aranea uddmanni
Aranea scorpiformis
Aranea virginea
Aranea citrea
Aranea citrina
Aranea sulphereoglobosa
Aranea sulphurea
Aranea quinquepuncata
Aranea albonigricans
Aranea calicina
Aranea cretata
Misumena citrea
Thomisus citreus
Thomisus calycinus
Thomisus dauci
Thomisus pratensis
Thomisus spinipes
Thomisus scorpiformis
Thomisus quadrilineatus
Thomisus viridis
Thomisus phrygiatus
Thomisus devius
Thomisus fartus
Thomisus vatius
Pachyptile devia
Thomisus cucurbitinus
Misumena oblonga
Misumena calycina
Misumena occidentalis
Misumenops vatia

Cvetni pajek (znanstveno ime Misumena vatia) je holarktično razširjena vrsta rakovičarjev. To so rumeni ali beli pajki, kar je odvisno od cveta, na katerem prežijo. Samice zrastejo do 10 mm (brez nog), samci največ do 5 mm. Posebno mlade samice, ki lahko lovijo na različnih cvetovih, npr. marjeticah in sončnicah, se lahko prilagajajo barvi cveta. Starejše samice potrebujejo za čim bolj kvalitetna jajčeca velike količine razmeroma velikega plena.

Razmnoževanje

Samec M. vatia

Mnogo manjši samci se pri iskanju samic hitro selijo s cveta na cvet. Zaradi napadov plenilcev (npr. ptičev) ali boja z drugimi samci so pogosto brez ene ali več nog. Ko najdejo samico, splezajo čez njeno glavo in zadek na njeno spodnjo stran, kjer vanjo vstavijo svoje pedipalpe in jo oplodijo.

Mladiči do jeseni dosežejo velikost okrog 5 mm in prezimijo na tleh. Zadnjič se levijo maja naslednje leto.

Spreminjanje barve

Samica cvetnega pajka na navadnem rmanu (Achillea millefolium)

Cvetni pajek

Cvetni pajki lahko svojo barvo spreminjajo s pomočjo tekočega rumenega pigmenta (kinurenin in 3-hidroksikinurenin),^[1] ki ga izločajo (secernirajo) v zunanjo plast celic na telesu. Na beli osnovi se prenese v nižje plasti, tako da postanejo vidne notranje žleze, napolnjene z belim gvaninom. Če se pajek dolgo zadržuje na beli rastlini, se rumeni pigment pogosto izloči. Tedaj pajek za spremembo barve potrebuje precej več časa, saj mora najprej sintetizirati nov pigment.

Sprememba barve z bele v rumeno traja med 10 in 25 dni, v nasprotni smeri pa šest dni. Sproži jo vidna povratna zanka. Pajki z obarvanimi očmi so sposobnost spreminjanja barve izgubili.

Reference

Blomkrabbspindel (Misumena vatia) är en spindelart i familjen krabbspindlar.

Kännetecken

Honorna, som är större än hanarna, kan bli upp till 10 mm i kroppslängd medan hanarna blir maximalt 5 mm. Dessa spindlar kan ha varierande färg beroende av vilken blomma de sitter på. Vanligaste färgerna är vita eller gula med strimmor och fläckar av rött eller lila, men de kan även vara av en heltäckande färg. Hanarna är av helt annan färg och teckning.

Namnet krabbspindel kommer ifrån att den liknar en krabba i sina utsträckta främre ben och i dess förmåga att gå i sidled likt en krabba.

Utbredning

Blomkrabbspindeln är ganska vanlig i den holarktiska regionen. I Sverige är den vanlig över hela landet.

Levnadssätt

Blomkrabbspindel som fångat en Skogsgräsfjäril.

Blomkrabbspindeln använder sig inte av nät utan jagar genom att vänta ut sina byten, oftast sittande på en blomma med främre benen utsträckta för att snabbt greppa tag i bytet. Den skapar en silkestråd som den använder sig av som livlina om den skulle tappa greppet där den sitter, men även för att flyga (se nedan). Den byter färg efter den blomma den sitter på. Det tar spindeln ca 24 timmar att byta färg. Man har trott att anledningen till detta beteende är att kamouflage ger en ökad chans till fångst av byten, men studier från 2009 visar att de inte fångar fler byten än om de placeras på en blomma där de inte är kamouflerade. Inte heller utsattes de för fler attacker från rovdjur som fåglar.^[1] Blomkrabbspindlar kan fånga ganska stora byten, vilket kan ses på bilden på denna sida där en hona tagit en Skogsgräsfjäril.

En Blomkrabbspindel med byte på södra Gotland

Blomkrabbspindlar har förmågan att, så att säga, flyga när de känner sig hotade men även då de vill flytta till nytt område vilket de verkar göra med jämna mellanrum. På den blomväxt de sitter på ställer de sig med baken i vädret och skjuter ut tunn silkestråd som förs med vinden och fortsätter skjuta ut trådar lite då och då tills de får en att fastna i en närbelägen växt, till exempel ett högt växande strå. De trådar som inte fastnar i något tar de och hovar in och käkar upp då det är värdefull materia. När en tråd fastnat klättrar de över till den nya platsen och klättrar upp så högt de kan. Har de inte lyckats komma till en ny plats som de kan klättra högt upp på så gör de om försöken, men om de lyckats komma på en hög växt eller långt strå så klättrar de upp allra högst upp och som det verkar så skjuter de iväg trådar för att känna efter vindens kraft tills den är kraftig nog och då skjuter de ett stort moln av silke som blir till ett segel som kan bära iväg spindeln på höga höjder och stora distanser. På dessa höjder blir de ofta föremål för rovdjur som fåglar och trollsländor. När de blir attackerade släpper de silkesseglet och sträcker ut sina främre ben varvid de seglar ner till marken.

Referenser

Noter

1. ^ Enligt fältstudier gjorda av Rolf Brechbühl, Jérôme Casas och Sven Bacher från Biologiska Fakulteten vid Universitetet i Fribourg, Schweiz.

Källor

Rolf Brechbuehl, Jerome Casas, and Sven Bacher (October 2009): "Ineffective crypsis in a crab spider: a prey community perspective"

Externa länkar

• Wikimedia Commons har media som rör Blomkrabbspindel.
  Bilder & media

Misumena vatia, Thomisidae familyasından Holarktik bölgede yaşayan bir örümcek türü. Almanya'da 2006 Yılın Örümceği olarak seçilmiştir.

Tarihçe

İlk kez 1757 yılında İsveçli entomolog ve araknolog Carl Alexander Clerck (1709-1765) tarafından Araneus vatius adıyla tanımlanan tür 1872 yılında İsveçli araknolog Tamerlan Thorell (1830-1901) tarafından Misumena vatia adıyla revize edilmiştir.

Teşhis anahtarı

Tür teşhis karakteri (Türkiye için): Abdomen renkleri çeşitli olup beyazdan açık sarıya veya yeşile kadar renklerle bezenmiş^[1].

Morfoloji

Seksüel dimorfizm boyca ve renkçe belirgindir. Dişi 7–10 mm, erkek 3–5 mm boyundadır^[2]. Yan gözeler belirgin olarak çıkıntılıdır. Karapaksın orta kısmında beyazımsı yeşil bir şeritleşme görülür. Abdomen yeşilimsi beyaz olup üzerinde koyu benekler mevcuttur. I. ve II. bacaklar oldukça iri ve uzundur. Patella I ve II ile femur yeşilimsi sarı segmentler bulundurur. Tibia yumruludur^[1]. Dişiler çiçeğine göre değişken renkteyken, erkekler ağırlıklı olarak kahverengidir.

Habitat

Alçak vejetasyon üzerinde çiçeklerin, çalıların ve otların üzerinde yaşarlar.^[1]. Büyük Britanya'da çalı ve otlar arasındaki sınır bölgelerde görüldüğü gibi açık alanlarda da rastlanır.^[3].

Yaşam döngüsü

Büyük Britanya'da her iki cinsiyetten erginlerine mayıs-ağustos aylarında, en çok da mayıs ve haziran aylarında rastlanır, bazen dişiler sonbahara kadar görülebilir hatta kışı sağ geçirebilir ve mart ayında da görülebilir^[3].

Yayılımı

Holarktik bölgede yayılım gösterir^[4]. Avrupa'da özellikle güney Avrupa ülkelerinde yaygındır. Büyük Britanya'da İngiltere ile Galler'in güney yarısında yaygındır^[3]. Kuzey Amerika'da en iri ve en çok bilinen çiçek örümceğidir.

Türkiye'deki durumu

Türkiye'de^[5] cinsinin tek türüdür. Marmara ,Karadeniz ve [ [Ege bölgesi/İzmir] bölgelerinden kayıt vardır^[1]

Kaynakça

Dış bağlantılar

• http://wiki.spinnen-forum.de/index.php?title=Misumena_vatia (Almanca)
• http://crocea.wordpress.com/thomisidae/ (Norveççe)

• 1 Опис
• 2 Спосіб життя
  • 2.1 Живлення
  • 2.2 Відтворення
  • 2.3 Статева поведінка
• 3 Розповсюдження
• 4 Таксономія
• 5 Галерея
• 6 Примітки
• 7 Джерела

1. ↑ Riou, Mickaël; Christidès, Jean-Philippe (2010). Cryptic Color Change in a Crab Spider (Misumena vatia): Identification and Quantification of Precursors and Ommochrome Pigments by HPLC. Journal of Chemical Ecology 36 (4): 412–423. ISSN 0098-0331. doi:10.1007/s10886-010-9765-7.(англ.)
2. ↑ Morse, 2007, c. 19
3. ↑ Morse, 2007, c. 17
4. ↑ Morse, 2007, c. 12
5. ↑ Platnick, Norman I. (2016): The world spider catalog, version 16.5. American Museum of Natural History

Misumena vatia Clerck, 1757

Цветочный паук^[1] (лат. Misumena vatia) — вид пауков семейства Пауки-бокоходы (Thomisidae).

Описание

У вида выражен половой диморфизм в размере и окраске. Самцы длиной 4 мм, в то время как самки длиной до 10 мм. У самца головогрудь (просома) черноватого цвета, брюшко (опистосома) от белого до желтоватого окраса с двумя тёмными длинными полосами. Обе передние пары ног с широкими полосами чёрного и коричневого цвета, обе задние пары ног основного цвета брюшка.

У самок окраска всего тела варьирует от ярко-жёлтого до жёлто-зелёного и белого. Часто на боковых сторонах брюшка имеются две длинные красные полосы.

Распространение

Вид распространён от арктической до субтропической зон Голарктики от Ирландии и Португалии до Японии, а также от Аляски до южной границы США. За исключением Исландии вид обитает во всей Европе.

Вид населяет открытые местообитания с большим количеством цветущих растений. Половозрелые пауки могут встречаться с мая по июль.

Питание

Свою добычу паук подстерегает на цветках. Он может менять свою окраску в зависимости от окраски цветов. Эту способность имеют только половозрелые самки. Они управляют изменением пигментации тела своими органами зрения. При окраске в жёлтый цвет в клетки эпидермиса поступает жидкое, жёлтое красящее вещество, при окраске в белый цвет пигмент переносится во внутреннюю часть тела. Жёлтый пигмент может выделяться при продолжительном пребывании на белых цветках также с испражнением.

Добычей цветочного паука являются различные насекомые-опылители, например, журчалки, пчёлы, осы, бабочки или небольшие жуки. Они часто на порядок крупнее самого паука. Паук схватывает свою добычу сильными, широко расставленными передними ногами и молниеносно наносит укус в голову. Паутину не плетёт.

Размножение

Спаривание происходит ранним летом. Когда самец находит самку, он влезает спереди на её спину. Затем он перемещается на брюшную сторону самки и в позиции брюшко-к-брюшку попеременно вводит свои педипальпы в половое отверстие самки. Затем он снова влезает на спину самки, чтобы после перерыва снова спариться с ней. В конце концов, самец покидает самку. Коконы яиц располагаются скрытно с боков цветков. Молодые пауки зимуют в земле.

Примечания

弓足梢蛛（拉丁文學名：Misumena vatia），又名弓足花蛛、姬花蛛或秋麒麟蟹蛛^[1]，是分佈在全北區的一種蟹蛛。

雄性弓足梢蛛較雌性細小，最大只有5毫米，而雌性則可達1厘米。雌性幼蛛在初夏很細小，並不起眼。

弓足梢蛛可以呈黃色或白色，看牠們所在的花朵而定。雌幼蛛更會在多種的花上獵食，如雛菊及向日葵，故彷彿可以「隨意」變色。年長的雌蛛相對需要較大的獵物來產卵。

繁殖

雄性弓足梢蛛

雄性弓足梢蛛會由一朵花到另一朵花尋找雌性，往往在過程中會遇上掠食者或與其他雄性打鬥而失去一條或多條腿。當發現雌性的時候，雄性會爬到雌性的頭及末體到達其底部，並會將牠的觸肢插入來使雌性受精。

幼蛛到了秋天就可以生長達5毫米，並會在地上過冬。翌年5月牠們會脫殼。

變色

雌性弓足梢蛛

弓足梢蛛

弓足梢蛛會在身體最外層的細胞分泌一種黃色液體色素，以達成變色的效果，這種色素其實是犬尿氨酸及3-羥基犬尿氨酸。^[2] 這種色素可以傳送至較底層，從而可以見到充滿白色鳥嘌呤的內腺，令弓足梢蛛變成白色。若牠們在白色花朵上較長時間，這些黃色色素會被排出。由於要重新分泌色素，牠們故要較長時間才能再變為黃色。一般而言，由白色轉變為黃色所需時間為10-25天，相反的則只要6天。

弓足梢蛛的變色是由視覺引發的。在弓足梢蛛的眼睛上塗上顏色，便會失去了變色的能力。

參考資料