Cantharidin

Definition

A terpenoid compound and potent vesicant secreted by blister beetles (Meloidae) as a chemical defense against predators. In nature, males synthesize cantharidin and transfer it to females as a copulatory gift; females subsequently apply it to eggs for protection. The compound causes blistering of skin and mucous membranes and is toxic in quantity, though it has legitimate medical applications in dermatology for treating warts and molluscum contagiosum.

Etymology

From Spanish cantharide, from Latin cantharis 'blister beetle', from Greek kantharis

Example

The striped blister beetle (Epicauta vittata) sequesters cantharidin from host plants and concentrates it in hemolymph and reflex-bleeding fluids; horses consuming hay contaminated with even small numbers of these beetles can suffer fatal cantharidin toxicosis.

Related Terms

• meloid
• chemical defense
• Reflex bleeding
• terpenoid
• vesicant
• copulatory gift
• Sequestration
• aposematism

Usage Notes

Cantharidin is often mistakenly called a 'poison' in popular sources, but specialists distinguish between its ecological role as a defensive allomone and its pharmacological use as a keratolytic agent. The compound is stable and persists in dried beetles, making contaminated hay a serious veterinary concern. Do not confuse with cantharidin names in taxonomy (e.g., Phthia cantharidina, a coreid bug named for color resemblance, not chemistry).