American Snout

Libytheana carinenta — the American snout — is one of the most distinctive butterflies in the Americas and one of about 10 species in family Libytheidae (the snout butterflies — characterized by the diagnostic forward-projecting palp 'snout'). The species is widespread across the southern US, Mexico, Central America, the Caribbean, and South America with seasonal range expansion north to the central US. Adults are 4-5 cm wingspan with the species' two diagnostic features: (1) extraordinary FORWARD-PROJECTING 'SNOUT' formed by elongated MAXILLARY PALPS at the front of the head — the palps extend forward 4-5 mm beyond the head, looking like a small forward-pointing 'beak' or leaf-petiole. The snout is unique among NA butterflies and is the source of the family and species common name. (2) Brown-and-orange wings with white markings — the upperside has dark brown wings with bright orange patches and small white spots, and the UNDERSIDE is gray-brown with subtle markings that combine with the snout-shaped head to create a DEAD LEAF MIMIC appearance when the butterfly is at rest with wings folded. The leaf-mimic camouflage: when American snouts rest on tree branches with wings folded above the back, the brown underside wings look exactly like a dead oak or hackberry leaf (color-matched to typical dead-leaf brown), the snout perfectly mimics the petiole (the small stem connecting a leaf to the branch), and even the wing veins resemble leaf veins. The combined effect makes the resting butterfly essentially invisible against tree bark and dead leaves on twigs. The species is also famous for occasional MASSIVE OUTBREAK MIGRATIONS in south Texas. In years of favorable rainfall and abundant SPINY HACKBERRY (Celtis pallida — the species' larval host plant in south Texas), American snout populations can build to extraordinary outbreak densities. During major outbreaks, HUNDREDS OF MILLIONS OF AMERICAN SNOUTS migrate together northward through south Texas in flying clouds DENSE ENOUGH TO BLOCK SUNLIGHT (the migrating butterfly density is high enough to dim daylight in heavily-affected regions), SLOW HIGHWAY TRAFFIC (drivers must reduce speed because of the impossibility of seeing through clouds of butterflies, and because of accumulated butterfly bodies on windshields and grilles), and DRAMATICALLY ALTER DAILY LIFE (schools dismiss early, outdoor events are canceled, residents sweep dead butterflies from doorsteps and patios). Major historical outbreaks include 1996, 2002, 2010, and 2017 — each generating widespread media coverage and surprised wonder from south Texas residents. The outbreak migrations are one of the most spectacular insect migration events in North America. The species is restricted to forests with HACKBERRY (Celtis) host plants — larvae feed only on hackberry leaves. The species is harmless to humans (no venom, no bite, no urticating hairs — just a remarkable insect with extraordinary biology).