I [introduced species]
Taxonomic comments
Workers of W. auropunctata have a strongly quadrate petiolar node. The anterior face of the node is sharply differentiated from both the peduncle and the dorsal face of the node, meeting both at nearly right angles, and forming a strongly step-like profile. This is a highly distinctive feature that easily distinguishes auropunctata workers from all other Wasmannia species. Within the species there is abundant variation in the strength of sculpturing and coloration, and this has engendered the naming of nine infraspecific forms in addition to the nominotypical. We have never been able to discover evidence of discrete forms among the workers of auropunctata , either in sympatry or allopatry; the variation appears continuous. Three of the forms have already been synonymized by others: atomum , glabra , and panamana . We have been able to examine types of three additional forms — obscura , pulla , and rugosa — and they fall well within our concept of auropunctata . The remaining forms — australis , laevifrons , nigricans — we have not examined, but the published descriptions give no indication that they are beyond the range of variation of auropunctata . We have synonymized them, following the philosophy that taxa should be synonymized unless evidence of distinctness is obtained.
The above synonymy does not assure that there is no genetic structuring, and perhaps species-level differences, within the broad concept of auropunctata . There may even be distinct sympatric species. In Costa Rica, there appear to be two size classes of queens (Fig. 2). Queens with smaller heads include ten from various sites in Costa Rica, including La Selva Biological Station and the Penas Blancas Valley, one from Jamaica, and one from Venezuela. Queens with large heads are all from the Atlantic slope of Costa Rica. Three are from La Selva (two from different Winkler samples of sifted leaf litter from the forest floor, one from a small nest under an epiphyte mat in an old treefall) and one is an alate queen found in a Cecropia sapling near Volcan Arenal. Thus the small-headed and big-headed forms are broadly sympatric in Costa Rica. Among the small-headed queens four are definitively associated with workers from the same colony, and among the big-headed queens one is associated with workers. Others have workers doubtfully associated (together in the same Winkler sample). We can discern no differences in workers associated with the two types of queens. The cause of the two size classes of queens is unknown, but could reflect either differences between cryptic species or intraspecific polymorphism.
An aberrant worker form is frequently encountered in large samples of W. auropunctata . These aberrant workers have the head grossly swollen. The entire head is more spherical than normal, as if the head were inflated like a balloon. The rest of the body is little different from a normal worker. These aberrant workers are occasionally encountered in Winkler samples that contain hundreds or thousands of auropunctata workers.
Natural History
Wasmannia auropunctata is a widespread pest ant (Clark et al., 1982; De Souza et al., 1998; Fabres & Brown, 1978; Jourdan, 1997; Lubin, 1984; Ulloa Chacon & Cherix, 1990; Williams, 1994; Wetterer & Porter, 2003). In its presumed native range it occurs from Argentina to Mexico (Kempf, 1972; Wetterer & Porter, 2003). Its introduced range includes the Galapagos Islands, West Africa (Gabon, Cameroon, and possibly the Republic of Congo and the Democratic RepubIic of Congo), Melanesia (New Caledonia, Solomon Islands, Vanuatu, and possibly Tuvalu), Polynesia (Wallis and Futuna and Hawaii), parts of the US (Florida and possibly California), and subtropical Atlantic islands (the Bahamas and Bermuda) (Wetterer & Porter, 2003). It is widespread on Caribbean islands, but it is unclear whether these are long-term native populations or recent introductions (Wetterer & Porter, 2003).
The species is remarkably catholic in its habitat preference. It is common in habitats ranging from wet to dry and from early successional to mature. In an elevational gradient of mature wet forest on the Atlantic slope of Costa Rica (the Barva Transect, from La Selva Biological Station to 2000 m elevation on the slope of Volcan Barva) it is abundant at 50 m and 500 m elevations, but nearly absent at 1070 m (Table 2). In the lowland habitats where it is abundant, it occurs in leaf litter on the forest floor and at all levels in the vegetation.
Although it occurs frequently in samples from mature forest habitats in Costa Rica, it is never so abundant in those habitats that it is noticeable as a pest or appears to be displacing other native species (Tennant, 1994; McGlynn & Kirksey, 2000; pers. obs.). In contrast, in certain agricultural habitats (banana plantations) and in parts of the tropics where it has been introduced it becomes super-abundant, with negative impacts on native species and human comfort (Clark et al., 1982; Wetterer & Porter, 2003). In dry-forest fragments in Colombia there is a negative correlation between W. auropunctata abundance and overall ant diversity (Armbrecht & Ulloa Chacon, 2003). Where introduced in New Caledonia it invades dense native forest and displaces native ants (Le Breton et al., 2003). Behavioral tests and cuticular hydrocarbon analysis show that W. auropunctata is multicolonial in its native range in Brazil, unicolonial where introduced in New Caledonia (Errard et al., 2002).
The sting of Wasmannia is noteworthy. These are extremely tiny ants, barely visible in the field. When the senior author first began studying ants in Costa Rica, he was at first puzzled about Wasmannia . By literature accounts Wasmannia was reputed to have a terrible sting, but he had been collecting them for months in Corcovado National Park without ever experiencing the famous sting. One day he was collecting from a populous nest and some workers made it up to the soft skin of his inner forearm and began to sting. The sting was definitely noticeable, about as severe as a fire ant (i. e., Solenopsis geminata ) but inordinately strong for an ant that could barely be seen! Workers are so small they cannot sting through the thicker skin of the hands.
Surprisingly, the chemical and toxicological nature of the venom of W. auropunctata has not been investigated. Howard et al. (1982) discovered an alkylpyrazine compound in the mandibular glands, which acted as an attractant to conspecifics and a repellent to heterospecifics. They speculated that the workers might apply the mandibular gland product as an irritating secretion, augmenting the defensive properties of the venomous sting. It would be interesting to investigate whether the venom alone is the powerful agent in this small ant, or if the strong burning sensation is a synergetic effect of venom plus mandibular gland product.
Nests can be almost anywhere: in rolled leaves or dead sticks in the leaf litter, under stones, in rotten wood, in hollow stems suspended above the ground, in ant-plant domatia, and under epiphytes. Workers are omnivorous scavengers and predators and can rapidly recruit to food. Colonies are polygynous and it is never clear where colony boundaries are. Dozens of dealate queens may be found together in nests. Males are rare but do occasionally occur.
Boquerón , Caaguazú , Canindeyú , Central, Pte. Hayes (ALWC, IFML, INBP, LACM, MHNG MSCN, MZSP). Literature records: Alto Paraná , Concepción (Emery 1894a, Emery 1906, Forel 1907b; [also as “ australis ”, “ nigricans ”, and “ rugosa ”]).
(No. 39 a, b, c, d, e, f, g, h, i, j, k, l, vi, n, o, q, r, s, t, u, et 48 c bis), [[ worker ]] [[ queen ]] [[ male ]], [[ queen ]] (Inedite). L. 4 a 4, 3 mill.; thorax large de 1, 0 a 1,1, abdo- men de 1, 3 mill. Le thorax beaucoup plus large que la tete. Tete beaucoup plus large que longue et beaucoup plus large derriere que devant, largement concave derriere. Occiput subtronque. Pronotum epaule devant. Mesonotum subdeprime. Metanotum pourvu de deux epines extremement larges, triangulaires et assess longues qui se prolongent en aretes un peu translucides jusqu'au lobule metasternal qui est lamelliforme. Premier article du pedi- cule avec un petiole beaucoup plus long et plus fort, et un n oe ud plus court que chez l'ouvriere.
Tete et thorax longitudinalement rides-stries, mats et tres finement reticules-ponctues entre les rides. Pedicule et 1 er segment de l'abdomen tres finement et densement reticules-ponctues et mats (le dernier en partie reticule et subopaque ainsi que les pattes). Le pedicule a en outre quelques impressions longitudinales. Les autres segments abdominaux tres faiblement chagrines et luisants. Le premier segment de l'abdomen n'a pas les gros points enfonces de la [[ worker ]] et du [[ male ]].
D'un brun roussatre ou jaunatre, ferrugineux. Dessus de la tete et du thorax ainsi que le milieu des segments abdominaux d'un brun chatain. Ailes teintes de brunatre, pubescentes; nervures et tache marginale brunes. Du reste comme l'ouvriere, en particulier la pilosite et la pubescence, les aretes frontales, etc.
[[ male ]] (inedit). L. 4, 2 mill. Yeux grands, rapproches du bord anterieur de la tete. Mandibules dentees. Epistome sans carene. Scapes longs comme les deux premiers articles du funicule reunis. Premier article du funicule tres court, a peine plus long que large; second article d' 1 / 4 plus long que le 3 me. Face basale du meta- notum bien plus longue que la face declive; metanotum portant deux tubercules lateraux allonges. Premier article du pedicule avec un petiole large et un n oe ud arrondi, fortement elargi vers sa base. Valvules genitales exterieures terminees par deux immenses appendices longs, etroits, recourbes en bas, faiblement elargis vers leur extremite, longs comme les 2 / 3 de l'abdomen et depassant d'autant son extremite. Ces singuliers appendices qui ne sont qu'un prolongement demesure de l'extremite des valvules exte- rieures, donnent a ce male un aspect tout particulier. Mesonotum avec un large sillon median anterieur, deux sillons convergents et deux sillons lateraux posterieurs.
Tete et thorax densement reticules-ponctues et mats, avec quelques rides (quelques stries sur la tete). Metanotum en outre fortement ride en long. Pedicule reticule et subopaque. Abdomen luisant, faiblement reticule; sur le premier segment de gros points enfonces irreguliers. Pilosite et pubescence comme chez la [[ queen ]] et l'ouvriere, mais plus pointue et plus fine.
D'un brun fonce ou noiratre. Cotes du thorax, pattes et funicules d'un brun jaunatre sale. Mandibules, scapes, tarses, extre- mite des segments abdominaux, et appendices genitaux d'an jaunatre sale. Ailes d'une teinte un peu plus noiratre que chez la [[ queen ]].
(39). A very common species. The communities ave generally rather small, but may be composed of several hundred, or even a thousand, individuals. The formicaria are very simple, advantage being taken of a space among rotting leaves on the ground, or there is a single chamber - sometimes two or three close together - - under a stone or stick, at the roots of grass, or under bark, nearly always in a damp place. In this the ants are found closely packed, with a single female, or several, if the community is large, and the eggs and larvas. The workers are sluggish in their movements, and the females still more so. The workers are frequently found on foliage, forest or open land.
(39 a). Oct. 11 th (leeward). Forest above Chateau- belais, 1000 ft.; under a stick.
(39 b). Near Fort Charlotte, Kingstown, 500 ft. Oct. 25 th. Small nest under the side of a stone; thickets. Several males but no female found.
(39 c). Fitz-Hugh Valley (leeward), 500 ft. Nov. 4 th. Open place. Nest under log, and partly under the bark, with several chambers.
(39 d). Several nests. Localities and dates, not noted.
(39 e). Near Golden Grove House (leeward), 500 ft. Oct. 6 th. Coco orchards, among rotting leaves, under stones, & c. Several colonies; in one large one (several hundred workers) I could find no female. Some were taken on foliage.
(39 f). Same locality and date as No. 89 e. A small colony, under a stone.
(39 g). Bowwood Valley, near Kingstown, 800 ft. Oct. 21 st. Open place under a stone. Small colony.
(39 h). Near Palmyra Estate (leewardi, 1000 ft. Nov. 3 rd. Open place; under a log; between rotting leaves.
(39 i). Wallilobo Valley (leeward), Nov. 5 th. 5000 ft. Forest. Small nest under sod on a rock.
(39 j). Wallibou (leeward); seashore thickets. Oct. 7 th. Small nest under a stone.
(39 k). Old Botanical Garden, Kingstown; second growth. A small nest, in rotting-wood.
(39 l). Forest above Chateaubelais, 1000 ft. March. A single female, under rotting leaves.
(39 m). Open land and forest, 1500 ft. to sea-level. Beaten from foliage. Various localities and dates.
(39 n). Various localities and dates; forest or open land below 2000 ft. Taken from small nests, or found among rotting leaves.
(39 o). Southern end of island; Villa Estate. Oct. 14 th. Seashore thicket. Small nest under a block of coral (doubtfully referred to this species).
(39 q). Petit Bordelle Valley, 1600 ft. Nov. 13 th. Clearing. A small nest in rotten wood.
(39 r). Camden Park Estate (leeward), north of Kingstown. Nov. 19 th. Small nest under the bark of a palm-log; seaside thicket. No female could be found.
(39 s). Windward side, Robocca to Grand Sable Estate. Jan .. 2 nd and 3 rd. From several nests in various localities near the seashore; under stones.
(39 t). Windward, Grand Sable Estate; open place near the sea. Community of about 500, under a stone. Jan. 3 rd.
(32 u). Sandy bed of Dry River (windward), near sea. Jan. 2 nd. Under a stone. Associated with No. 34 c.
(48 c bis). Females found without workers; under sod on rocks; different localities near sea-level (leeward), and south end of island. November.
[[ worker ]]. La Caja, pres San Jose de Costa Rica, 1100 metres, Costa Rica (P. Biolley), Costa Rica (J. - F. Tristan).
