Greta oto is a brush-footed butterfly, and is a member of the clearwing clade; its wings are transparent. Its most common English name is glasswing, and its Spanish name is espejitos, which means “little mirrors.”
Indeed, the tissue between the veins of its wings looks like glass.
It is one of the more abundant clearwing species in its home range, which extends throughout Central America into Mexico. The opaque borders of its wings are dark brown sometimes tinted with red or orange, and its body is dark in color. Its wingspan is between 5.5 and 6 cm.
Adults inhabit the rainforest understory and feed on the nectar of a variety of tropical flowers. G. oto prefers to lay its eggs on plants of the tropical nightshade genus Cestrum. The silvery-gray caterpillars feed on these toxic plants and store the alkaloids in their tissues, making them distasteful to predators such as birds.
They retain their toxicity in adulthood. The same alkaloids that make them poisonous also are converted into pheromones by the males, which use them to attract females. G. oto adults also exhibit a number of interesting behaviors, such as long migrations and lekking among males.
This is an unusual butterfly in which the forewings are transparent like glass, hence the common name. It has a slow graceful gliding flight, but if disturbed can make off with great speed.
The slow flight is typical for poisonous species of butterflies that gives predatory birds sufficient time for recognition. The butterfly is readily visible in flight. Males are often seen hill topping. Both sexes are easily approached during normal flight.
The entire life history of this butterfly is poisonous. Its passion-vine foodplants contain poisons which the larva of the glasswing is able to assimilate and retain in its body as a protection against vertebrate predation. These poisons are cyanogenic glycosides, which release hydrocyanic acid when ingested.
The poisons are passed on to the pupa and the adult butterfly. The latter can further top up its poisons by imbibing (sucking and assimilating) the sap and surface exudates from from other poisonous plants. The cardiac glycoside poisons are passed onto the eggs by the female to complete the cycle.
These poisons are usually in sufficient concentrations to only sicken the vertebrate predators, so that they can both learn from the experience and pass on the knowledge. They are not meant to cause death as this would likely result in larger numbers of the butterfly being killed.
The butterfly belongs to a subfamily group within which most of the included butterflies and their early stages are poisonous, providing models for mimic butterflies. The early stages have characteristic shapes. The adult butterflies usually have bright wing colours. Members of the Acraea generic group are well developed in Africa, from where the single Australian species probably had its evolutionary origin. They are closely related to the Heliconiids in the Americas.
Sources – South Australian Butterflies and Wikipedia
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