Meloidae

Meloidae, commonly known as blister beetles, is a family of beetles within the order Coleoptera. The family comprises roughly 2,500–3,000 described species worldwide, with greatest diversity in temperate and arid regions. Adults are typically found on flowers or foliage, where they feed on nectar, pollen, or plant tissues. Larvae are highly diverse and undergo hypermetamorphosis, with early instars adapted for dispersal and host-seeking.

Most Meloidae are soft-bodied beetles with elongated bodies. Many genera have narrow, flexible elytra; in some groups like Meloe, the elytra are short and the abdomen more exposed. A hallmark of the family is cantharidin, a defensive toxin produced in specialized glands; this chemical can cause painful blisters on skin and is poisonous if ingested.

Life cycle and ecology: Eggs are laid on vegetation; first instar larvae (triungulins) are active and seek hosts. Depending on species, triungulins parasitize bee or wasp nests, or feed on grasshopper eggs; later instars resemble small grubs. Adults feed on nectar and pollen, and in some species on flowering hosts.

Ecology and human impact: Some species are agricultural pests, particularly in hay crops such as alfalfa, where beetles can contaminate hay and pose poisoning risk to horses. Others contribute to biological control by preying on pest insect eggs during the larval stage. The presence of cantharidin makes handling blister beetles a safety consideration.