Epicauta stuarti

Distinguished from similar-appearing soldier beetles (Chauliognathus spp., family Cantharidae) by the soft, flexible elytra characteristic of Meloidae and the broader, more robust body form. The black and orange pattern is nearly identical to that of the Colorado Soldier Beetle (Chauliognathus basalis) and its foothills relative C. deceptus, representing Müllerian mimicry where both chemically defended species share warning coloration. Can be separated from other Epicauta species by specific pattern details of the orange markings, though precise diagnostic features require expert examination.

Open habitats including shortgrass prairie, sand dune systems, and pinyon-oak-juniper woodlands. Associated with flowering plants, particularly Gutierrezia sarothrae (snakeweed).

North America; documented from Colorado, Oklahoma, New Mexico, and adjacent southwestern United States. Records suggest a western distribution with eastern extent into the Great Plains.

Adults active in late summer and early autumn; observed from August through October in field studies. Peak activity coincides with flowering of host plants and co-occurrence with soldier beetle species in the mimicry complex.

Adults have been observed feeding on flowers, particularly Gutierrezia sarothrae. Participates in Müllerian mimicry with soldier beetles (Chauliognathus spp.), sharing aposematic black-and-orange coloration that advertises chemical defenses to predators. When disturbed, exudes cantharidin from leg joints and body segments as a defensive secretion.

Contributes to Müllerian mimicry complex with soldier beetles, reinforcing predator learning of unpalatability. As a flower visitor, may play a role in pollination, though this has not been quantified. Larval ecology unknown but likely follows the hypermetamorphic pattern typical of Meloidae, with larvae preying on grasshopper eggs or bee nest provisions.

Produces cantharidin, a potent vesicant (blistering agent) that can cause painful, scarring skin blisters upon contact and is fatal if ingested. Represents a toxicity hazard to livestock that might consume the beetles in hay or forage. The mimicry complex involving this species has been highlighted in popular entomological literature as an example of convergent defensive signaling.

• Chauliognathus basalis (Colorado Soldier Beetle)Shares nearly identical black-and-orange color pattern; distinguished by hardened elytra, more slender body, and family Cantharidae characteristics
• Chauliognathus deceptusFoothills and mountain counterpart to C. basalis with similar color pattern; distinguished by same features as C. basalis
• Calopteron terminale (End Band Net-wing Beetle)Occurs in same habitats with similar coloration; distinguished by elytral structure with distinct net-like venation and family Lycidae characteristics
• Crossidius discoideusLonghorned beetle (Cerambycidae) with similar color pattern representing Batesian mimicry; distinguished by extremely long antennae and hardened elytra

• blister beetle
• Meloidae
• Müllerian mimicry
• aposematic coloration
• cantharidin
• southwestern US
• autumn active
• flower visitor

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Meloidae Holdings | Entomology Research Museum
• Bug Eric: A Beetle Mimicry Complex
• Insecta | Beetles In The Bush | Page 3