Altica subplicata is generally known to find and accept host plants based on phenolic glycoside content. Many similar species also sequester compounds that are used as defense. This is well documented in some Chrysomelinae, and it is suspected that A. subplicata sequesters defense compounds as well. Willow leaf beetles communicate with other beetles through touch, during mating and aggregation, and can detect each other visually. They can also sense their environment visually, with smells and chemicals, and through touch.
Communication Channels: visual ; tactile ; chemical
Other Communication Modes: pheromones ; scent marks ; vibrations
Perception Channels: visual ; tactile ; vibrations ; chemical
This species is not a conservation concern, but it is a major herbivore on dunes habitats along the Great Lakes where several other threatened or endangered species occur.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Eggs of A. subplicata are laid in the spring. Larvae hatch after about 7 days, and go through 3 larval instars, during which the larval instars feed. After about 16 days, the larvae move underground and form pupal cells using mucus secreted by maxillary glands. Larvae use moist sand as a pupation site. The pupal period lasts 1 week or more depending on weather conditions. The adults emerge and feed through the rest of the summer. During the first cold nights of autumn, adults leave the host plant and overwinter in leaf litter, under stones, logs, and bark. Adults emerge in the spring, find mates, and then oviposit on host leaves. In total, one generation takes about 34 days to complete, with the resulting adults living for an extended period of time after emergence.
Development - Life Cycle: metamorphosis ; diapause
There are no known adverse affects of Altica subplicata on humans.
There are no known positive effects of Altica subplicata on humans.
Bach (1990) documented that Altica subplicata affects plant species composition and potentially succession on sand dunes in the Great Lakes region. In outbreak years, this species severely defoliates its host plant, and likely modifies its reproductive capabilities, causing non-host plants to be more abundant in areas with high beetle density. A. subplicata may be a competitor with other willow-feeding beetles, particularly Disonycha alternata on Salix interior.
Species Used as Host:
Altica subplicata is a specialist herbivore on willows. Along rivers over much of the range, this beetle feeds primarily on Salix interior, the sandbar willow, but it will also feed on Salix amygdaloides. On the shores of the Great Lakes it feeds on Salix cordata, the sand dune willow. Young larvae eat only on the underside of the leaves, while later instars and adults eat the entire leaf, leaving only the veins. Larvae are far more likely to feed on young leaves with a high density of trichomes. Adults will feed on older leaves, but are also more likely to eat younger leaves.
Plant Foods: leaves
Primary Diet: herbivore (Folivore )
Altica subplicata, the willow leaf beetle, is found north of Mexico, across the Nearctic region. It ranges from the southern most point of Texas to southern Canada from British Columbia to Quebec. The highest concentration of this species is along the Mississippi River and the Great Lakes, extending west to the Rocky Mountains.
Biogeographic Regions: nearctic (Native )
Altica subplicata thrives in sand dune habitats along the Great Lakes and on sand bars in rivers. The density of beetle populations decreases significantly with increasing distance from shore on the Great Lakes, and beetles are not found on plants further than 16 meters from the shore. Willow leaf beetles are more abundant on young dunes than intermediate or old dunes.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune
Other Habitat Features: riparian
A typical generation from egg to adult takes about 34 days. Adults live for an extended time after emergence. The final generation of adults enters diapause through the winter and starts mating and egg-laying again in the spring.
Typical lifespan
Status: wild: 2 to 12 months.
Altica subplicata has an oblong, oval body shape. The body is a dark metallic blue color, sometimes with deep violet reflections. Antennae and legs are the same color as the body. Larvae of A. subplicata are deeply pigmented. Females of this species tend to be larger than males. The elytra are low and weakly developed. The frontal tubercles are flat, and very finely alataceous and well defined posteriorly by post ocular sulci. It has a well defined coronal suture between the eyes, though the eyes are not prominent. The inner pair of setae are distinctly shorter than others. Willow leaf beetles have a quadrate pronotum with a deep transverse groove throughout. A. subplicata is distinguished from other low costate species as having a dull elytron surface with a deeper microsculpture.
Range length: 5.0 to 6.6 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; poisonous
Sexual Dimorphism: female larger
Carabid beetles of the genus Lebia are known to prey on Altica larvae, and are likely a predator of A. subplicata. It is possible that A. subplicata sequesters phenolic glycosides and uses these as defense, as is known for some willow-feeding Chrysomelinae. The bright, metallic blue coloration (likely aposematic) and aggregation behavior also suggest this could be true. The aggregation behavior itself also functions as a defensive mechanism, allowing both the larvae and the adults to appear larger and more intimidating.
Known Predators:
Anti-predator Adaptations: aposematic
Adults become sexually mature during winter. After overwintering, the willow leaf beetles appear on plants in early spring. The preoviposition period lasts 1 to 2 weeks, starting on the first day that the beetles appear on plants. Adults are very active during this period, flying around host plants looking for mates. To mate, the male mounts on the back of the female. Multiple matings are very common.
Mating System: polygynandrous (promiscuous)
Adults of Altica subplicata emerge from diapause in the spring and enter a prereproductive period of just over 1 week. They then start mating and ovipositing. Females deposit eggs horizontally in small clusters on the undersurface of young leaves of host plants, along the leaf veins. Up to 100 eggs can be found in an egg mass and a female can lay more than 400 eggs in a lifetime. The male to female ratio in an egg mass is 1:1. In the southern part of the United States, A. subplicata has 2 or more generations each summer. In northern states and Canada, A. subplicata has only one generation during the year.
Breeding interval: Willow leaf beetles produce 2 to 3 generations in southern states, but only 1 generation in Canada.
Breeding season: Willow leaf beetles breed in spring in the northern portion of their range, and may have a second summer generation in the southern portion.
Range eggs per season: 100 to 400.
Range gestation period: 1 to 2 weeks.
Range age at sexual or reproductive maturity (female): 31 to 37 days.
Range age at sexual or reproductive maturity (male): 31 to 37 days.
Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
There is no parental involvement in development other than provisioning of eggs.
Parental Investment: pre-hatching/birth (Provisioning: Female)
