Postman Butterfly

Heliconius melpomene — the postman butterfly — is one of about 50 species in genus Heliconius (the heliconiine longwing butterflies of the Neotropics) and one of the most extraordinarily-studied butterfly species in modern evolutionary biology. The genus has three biologically remarkable traits that make it scientifically important. First, POLLEN-EATING: Heliconius are the only butterflies known to consume pollen. Adults visit Psiguria and other Cucurbitaceae flowers, gather pollen on the proboscis, regurgitate saliva onto the pollen ball to liquefy it (extracting amino acids from the pollen grains), and drink the resulting amino-acid-rich liquid. The protein nutrition allows Heliconius adults to live 6-9 months (vs. 2-4 weeks for typical butterflies that survive on nectar alone). Second, MÜLLERIAN MIMICRY: H. melpomene and the closely related H. erato form geographically-aligned mimicry pairs across the Neotropics — at any given site, both species share the same wing color pattern (red-and-yellow bands on black, or all-blue patterns, or various combinations), and the matched warning coloration reinforces the warning signal to bird predators. Both species are chemically defended (they sequester cyanogenic compounds from larval Passiflora host plants), so the mimicry is mutualistic Müllerian rather than parasitic Batesian. Third, ADAPTIVE RADIATION: the genus is the centerpiece species in modern speciation research because Heliconius species have produced explosive recent radiation through wing-pattern divergence, hybrid speciation, and Müllerian convergence. The Mavárez et al. 2006 hybrid origin of H. heurippa was the first definitive demonstration of homoploid hybrid speciation in animals. The Heliconius Genome Consortium's 2012 sequencing of H. melpomene revealed the genetic basis of wing patterning (the optix and WntA genes are major loci controlling wing color and pattern across the genus). The species is widespread across South and Central America from southern Mexico to southern Brazil and is one of the most-studied butterflies in evolutionary biology research.