Blister Beetle Larvae
Blister Beetle Life Stages
Blister beetles belong to the Meloidae family of beetles. They are of importance since certain species are agricultural pests as well as potential medical pests. Adults are known to affect crops and contaminate hay. They produce a defensive compound, cantharidin. When interacting with the skin, it results in blisters, and if swallowed can lead to medical complications.
The United States has several species of blister beetle, though most are not significant pests. Like all other beetles, they have complete metamorphosis which includes egg, larva, pupa and adult. Adults are the most visible life stage, as they are moderately sized from 1 to 2.5 cm. Adult coloration varies, depending on the species, with some species being a solid gray color and others more brightly colored with yellow and orange. Eggs are laid in low-lying sheltered areas.
Most beetle larvae do not dramatically change form from one larval stage to another. However, blister beetle larvae are fairly unusual. The first blister beetle larva stage is radically different from the subsequent stages. For this reason, this type of metamorphosis is referred to as hypermetamorphosis.
The first blister beetle larval stage is highly mobile with well-developed legs. The larvae of some species even hitchhike on other insects like bees. The goal of the first larval stage is to locate a food source such as grasshopper eggs or bee nests in order to finish the rest of its development. The following larval stages are a different shape, more grublike, with fewer and shorter legs which results in them being not nearly as mobile. Many species of blister beetle survive the winter as late-stage larvae. The main goal of the larval stages is to grow as they feast upon their preferred food source. When they are ready to mature they will become pupae. The pupa stage is the transition stage where the grublike larva changes into the final adult stage. The adults then feed, mate and start the entire cycle over. Usually one generation of blister beetle is produced per year, but it is dependent on species and the seasons.