Heliconius melpomene martinae, Rio Claro, Colombia – Adrian Hoskins
Introduction
The tribe Heliconiini, colloquially known as Longwings, includes 71 species, all confined exclusively to the neotropics. The Heliconiini includes the genera Heliconius, Podotricha, Dryas, Agraulis, Dione, Dryadula, Eueides, Neruda, Laparus and Philaethria.
All Heliconius species have elongated black wings, marked with simple but striking patterns usually featuring streaks or patches of red and cream, or blue and cream. A few such as sara, antiochus and wallacei have a metallic blue sheen over the basal area of both wings. All are characterised by their delicate fluttering flight, long straight antennae, and fondness for flowers.
Heliconius melpomene is one of the commonest and most widespread of the Longwings, found from Mexico to Bolivia. It has no less than 29 named subspecies, many of which are Mullerian mimics of other Heliconius species – compare the images below of melpomene xenoclea and erato microclea. Both were photographed in the same forest glade at Satipo in Peru.
Heliconius melpomene xenoclea, Satipo, Peru – Adrian Hoskins
Heliconius erato microclea, Satipo, Peru – Adrian Hoskins
Habitats
Heliconius melpomene occurs at elevations between 0-1600m on both sides of the Andes although each of the various subspecies is restricted altitudinally as well as geographically. It can be seen flying in two’s or three’s around clearings, and along roads and tracks through primary forest, but seems to be more abundant in secondary forest.
Lifecycle
The eggs are yellow, and laid singly on the stipules and leaf buds of Passiflora. The caterpillar when fully grown is white with black spots, and branched black spines along the back and sides. The head is orange with a pair of recurved black spines. The pupa is brown with golden spots on the abdomen and thorax. It has long black spines on the abdomen and a series of short spines along the costa of the forewings on the wing pads. The head is bifid, with the labial palpi extended and twisted. The overall impression is of a decaying dead twisted leaf, hanging from a stem.
Adult behaviour
Heliconius butterflies are characterised by having a very delicate fluttering flight, particularly when hovering around flowers. They commonly nectar at Hamelia, Lantana and Palicourea.
Unlike other butterflies, Heliconius females feed on pollen as well as nectar. Studies of ethilla have shown that females deprived of pollen can only produce about 15% of the number of eggs laid by females that have access to it. This probably applies equally to other Heliconius species including melpomene. The pollen from Psiguria, Anguria and Gurania flowers provides amino acids that can’t be obtained from nectar or other sources, and contributes greatly to the longevity of the butterflies – some Heliconius species are known to live for up to 9 months as adults.
Studies have shown that Heliconius butterflies have home ranges within which they can memorise the locations of nectar and pollen sources, host plants and communal roosting sites. They are able to plan the most efficient route by which to visit all nectar / pollen sources in the vicinity by using simple calculations akin to what mathematicians call the “travelling salesman algorithm”. Erlich & Gilbert demonstrated that individual butterflies memorise the location of particular Psiguria plants, which they visit daily, following a predefined circuit through the forest.
In the genus Heliconius most species rely entirely on airborne chemicals to locate mates. Males of hecale, ismenius and cydno are attracted by pheromones to the pupae of conspecific females. The day before emergence a female pupa will usually have several males in close attendance. A frantic battle takes place the instant she hatches, as the males all struggle to copulate with her, not even allowing her time to expand and dry her wings. In some other Heliconius species such as hecalesia, hewitsoni, erato, charithonia and sara the males don’t even wait until the female emerges. Instead they physically break open her pupa and copulate as soon as her genitalia are accessible.