Chinese Bean Blister Beetle
Epicauta chinensis
A black-coated wanderer armed with toxic blood
The Chinese Bean Blister Beetle is a slender black beetle whose larvae change form dramatically several times, a pattern called hypermetamorphosis. Adults feed in groups on legume flowers and leaves and contain the toxin cantharidin; when alarmed, they ooze yellow blood (hemolymph) from their leg joints.
Key figures
- Length
- About 10–20 mm; slender-bodied, entirely black and covered in fine hairs
- Life cycle
- The larval stage passes through hypermetamorphosis with several distinct forms; the adult stage lasts about 1–2 months
- Habitat
- Farmland, legume crop fields, and grassland, where adults often gather in groups
- Diet
- Adults feed on the flowers and leaves of soybean and other legumes; larvae are parasitic, feeding on grasshopper egg pods
- Chemical defense
- When alarmed, it reflexively oozes yellow hemolymph from its leg joints, which contains the toxin cantharidin
- Hypermetamorphosis
- The first-instar larva — a mobile, three-clawed form called a triungulin — actively hunts down grasshopper egg pods to parasitize; later instars become plump and sluggish
Life cycle
Egg → Larva (hypermetamorphosis, parasitizes grasshopper eggs) → Pupa → Adult (1–2 months)
Ecological role
Chinese Bean Blister Beetle adults gather in groups to feed on the flowers and leaves of legume crops and are a common pest of soybean and similar crops; their parasitic larvae feed on grasshopper egg pods, giving them some suppressive effect on grasshopper populations too.
Did you know
Cantharidin from blister beetles has long been the source of the traditional Chinese medicine "ban mao," but the toxin is potent — even modest contact can blister the skin or cause poisoning.
Range
Most agricultural regions of China, especially common in the legume-growing areas of North and East China
Status
Common; an agricultural pest of soybean and other legume crops
Anatomy
- Elytra — Soft-textured wing cases (elytra) that cover the abdomen but part slightly at the tip, not fully enclosing it
- Neck — The thorax narrows markedly behind the head like a neck, a body shape typical of the blister beetle family (Meloidae)
- Head — Distinctly wider than the thorax and freely mobile, with compound eyes at its base on either side
- Antennae — Thread-like and slender, constantly probing for the scent given off by legume flowers and leaves while feeding
- Legs — The weak points at the joints ooze yellow hemolymph when alarmed, its main means of defense
- Abdomen — Soft and swollen, containing large amounts of cantharidin — the part used in traditional medicine and the source of its toxicity
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