Blister beetles, Epicauta sp. (Coleoptera: Meloidae), mating on Texas mountain laurel. Photo by Drees.
Common Name: Blister beetle
Scientific Name: Varies
Order: Coleoptera
Description: Blister beetles vary by species in shape, size (3/8 to 1 inch long) and color (solid gray to black or with paler wing margins, metallic, yellowish striped or spotted). Most are long, cylindrical narrow-bodied beetles that have heads that are wider than the first thoracic segment (pronotum). The wing (elytra) covers are usually soft and pliable. Although over 100 species occur in Texas, common blister beetles include:, the black blister beetle; Epicauta pennsylvanica (De Geer), E. occidentalis (east and central Texas) and E. temexa (south Texas) are mostly orangish-yellow with three black stripes on each of the wing covers (elytra). A west Texas species, Cysteodemus armatus
Black blister beetle, Epicauta pennsylvanica (DeGeer)(Coleoptera: Meloidae), on goldenrod flowers. Photo by Drees.
LeConte, has wing covers that are broadly oval and convex, colored black with bluish or purplish highlights.
Life Cycle: Complete metamorphosis; hypermetamorphosis. Winter is spent in later larval stages and pupation occurs in the spring. The pupal stage lasts about 2 weeks and adults appear in early summer. Female beetles lay clusters of eggs in the soil. The first stage (instar) larva hatching from the egg (triungulin) is a tiny, active, long-legged larva that seeks the appropriate host. Once there, the larva develops through a number of stages, each with progressively reduced appendages and increasingly grub-like in appearance. The first number of larval stages develop within about month, but the second to the last (pseudopupa) can remain for about 230 days before molting into the last (sixth) larval stage in the spring. Generally, one generation occurs per year although some develop in 35 to 50 days while in others, development takes 3 years.
A striped blister beetle, (Coleoptera: Meloidae). Photo by Drees.
Habitat and Food Source(s): Mouthparts are for chewing. Blister beetle species feed on flowers and foliage of a wide variety of crops including alfalfa, ornamental plants, potatoes, soybeans, garden vegetables and other plants. Immature stages feed on grasshopper eggs, live in solitary bee hives or are predaceous, depending on species. Adults can be found on flowers or infested crops. Care should be taken to not handle them. Never handle blister beetles preserved in alcohol because the cantharadin dissolves in alcohol and will cause blisters on the skin.
Pest Status: Adults usually occur in loose groups or swarms that feed on leaves of certain plants, especially legumes. Their bodies contain a toxin (cantharadin) that can cause blisters to form on the skin. Animals, particularly horses, ingesting beetle contaminated feed become extremely ill and may die. Handling blister beetles can cause blisters on the skin as a reaction to cantharadin. Larval stages feed on grasshopper eggs or are predaceous and are thus considered to be beneficial, although a few species feed in nests of solitary bees.
For additional information, contact your local Texas A&M AgriLife Extension Service agent or search for other state Extension offices.
Literature: Adams & Selander 1979; Borror et al. 1989; Dillon 1952; James & Harwood 1969; Metcalf et al. 1962; Swan & Papp 1972.