Butterfly of the Week: Cretan Festoon

Here's another small member of the swallowtail family. Despite its obvious resemblance to the other Festoons, some of which do have small swallowtails, Allancastria cretica (a.k.a. Zerynthia cretica and, two hundred years ago, Thais cretica) has rounded hind wings.

This one hardly seems bigger than the white clover blossom. It has the same range of color variations the other Festoons have, with some individuals almost all white, some showing more black or charcoal-gray than this one, and some bright orange-yellow. Females seem more likely to show creamy or yellow color above than males are. Really bright yellow individuals are rare, and are traded among museum collections. Undersides of the wings may look drab rather than white. 

A gallery of different live snapshots illustrates the variety of color patterns at https://lepiforum.org/wiki/page/Zerynthia_cretica .

Is it really a separate species, or just another sub-species of Allancastria cerisyi? Experts disagree. It's found only on Crete, where it can eat either of two species of pipevine, one called birthwort and one called Cretan birthwort. Without being sure whether it's a species, scientists can't begin to agree whether it's an endangered species, but like most butterflies its survival depends on the survival of the wild plants with which it coexists in balance.

The butterflies fly in spring. Females carefully place one egg on one leaf of each available host plant. 

From these eggs emerge little hungry caterpillars. Nature keeps many of the swallowtail species from overpopulating in a rather harsh way. The caterpillars always eat their own shed skins, including the shell of the egg from which a new-hatched caterpillar has emerged. This gives them an appetite for the skin of their own species and they don't seem to have any counterbalancing instinct not to harm their siblings. Without seeming to have any idea what they're doing, if they meet one another while they are caterpillars most swallowtails will eat one another alive. 

Not that they're particularly appetizing, or easy to ingest. The caterpillar's bristles suggest, but don't mimic, the branching spines of some venomous caterpillars and of many non-venomous mimics. They still seem meant to be discouraging to hungry birds.

It is crawling on a pipevine stalk. The butterfly's wingspan and the caterpillar's length can be over two inches. . 

Like several large butterfly caterpillars, larval Festoons may defoliate their host plants just before pupation, but this doesn't seem to harm the plant. 

 In autumn, the caterpillar pupates, shedding its warning-colors skin and adopting camouflage. It gets through the winter disguised as a broken twig. 

Not very well, to my eyes, but apparently the birds on Crete have learned that it's not good to eat, even if they can still see the shape of a caterpillar. Nice trick for those who can do it.