Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Superfamily: Papilionoidea
Family: Nymphalidae
Subfamily: Biblidinae
Tribe: Biblidini
Subtribe: Ageroniina
Genus: Hamadryas
Species: H. amphinome
There are 20 members of the genus Hamadryas, commonly known as Crackers due to the ability of several species to produce an audible signal that is similar to the crackling of bacon in a frying pan.
The sound is made only by males, and is produced as they take flight to intercept others of their own species. The crackling sound can be heard from several metres away, and is made by twanging a pair of spiny rods at the tip of the abdomen. Both sexes are capable of detecting the sound - their wings have tiny hollow cells covered in membranes which vibrate in response to sound waves, and stimulate nerve endings. The purpose of the sound is unproven - it may be an alarm signal but from my observations it appears to be a warning to other males that stray into each other's territory.
All Hamadryas species have a beautiful calico pattern on the upperside. In many there is a series of submarginal ocelli on the hindwings, and distinct kidney-shaped stigmata in the discal cells of fore and hind wings. In several species such as februa and glauconome the ground colour is greyish and the pattern acts as an extremely effective camouflage against the bark of trees. In other species such as amphinome, laodamia and velutina the wings are velvety black with a blue sheen and a pattern of bright blue markings. The blue colour is produced by light diffracting as it reflects back from microscopic prismatic ridges on the surface of the wing scales. The colour varies slightly according to the quality, intensity and angle of the light, so can appear as sky blue, cyan or even greenish in hue.
The common name Red Cracker refers to the colour of the underside hindwings.
Most Hamadryas species are found only in Central and South America, although 8 have been recorded sporadically in the southern USA.
Hamadryas amphinome is distributed from Mexico to Peru.
The Red Cracker is found in secondary or disturbed primary rainforest habitats at altitudes between sea level and about 1200 metres. It also occurs in dry or humid deciduous forests where it can often be abundant. In Guanacaste for example I found several basking on mango trees in a small orchard in the rainy season ( July ), together with februa, feronia and glauconome.
The eggs are white, and laid in chains of up to a dozen, hanging from the underside of leaves. The caterpillars when fully grown are black, with yellow marbling along the back, and have multi-branched spines that are black except for those on the middle section which are orange. They feed gregariously on Dalechampia scandens ( Euphorbiaceae ). The chrysalis strongly resembles a small withered leaf. It varies in colour from green to dark brown, and has a pair of flattened wavy head horns that are about half as long as the body. It is suspended by the cremaster from leaves or stems.
Like all Hamadryas species amphinome habitually basks on tree trunks in a head-downward position and with the wings flattened against the bark. They will bask in this position for long periods to await potential mates. They commonly settle at a height of about 2 metres but if disturbed by humans they fly up and resettle higher up, either on the same tree or on another nearby. They remain high in the trees until the intruder leaves, and then descend the tree trunk in a series of short flights, dropping a short distance each time until after several minutes they resume their original position.
The butterflies are active from sunrise to sunset, and are rarely seen away from tree trunks. They feed mainly on decomposing fruit.
