Glasswing Butterfly

• GeneralIts wings are transparent because they carry no pigmented scales.
• Its wings not only lack coloured scales: they are covered in irregular nanostructures that all but eliminate reflections, so that they do not even glint in the light, a principle being studied for making anti-reflective screens and lenses.
• The males take alkaloids from the dried flowers of plants of the genus Heliotropium and turn them into pheromones and defensive toxins, which they pass to the female during mating.
• It makes seasonal migrations of up to several hundred kilometres across Central America.
• Its wings are transparent, something exceedingly rare among butterflies. The tissue between the veins lacks colour scales, which is why it looks like glass.
• The transparency is not just an absence of scales: the membrane is covered in dome-shaped chitin nanoprotuberances that reduce reflection, so the wing does not absorb, does not scatter and barely reflects light. It is a natural anti-reflective coating studied in optics.
• It is toxic, and advertises it not with colours but with taste: it accumulates pyrrolizidine alkaloids from the plants it eats, both as a caterpillar and as an adult.
• Males convert those same alkaloids into pheromones and gather in leks, assemblies where they compete in display to attract females.
• It migrates up to 19 km a day at 13 km/h, moving between altitudes.
• Despite the fragility of its wings, it can carry up to forty times its own weight.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

The understorey of tropical rainforest

Size at birth

The caterpillar takes up the plant's alkaloids directly into its tissues, which makes it inedible; its extracts are rejected even by the bullet ant (Paraponera clavata)

Sexual maturity

A polygynous species: the males form leks in shaded parts of the forest, where they compete by displaying and release pheromones derived from the pyrrolizidine alkaloids they obtain from asteraceous plants

Gestation / incubation

The eggs hatch beneath the Cestrum flowers and the caterpillar starts eating the toxic plant at once; the chrysalis is chrome silver in colour and looks like a drop of water glinting on the stem, camouflage that in Costa Rica has earned it the name espejitos

Litter / clutch size

The mated female returns to a plant of the genus Cestrum (the nightshade family) and lays the eggs beneath its flowers

Sources consulted: https://es.wikipedia.org/wiki/Greta_oto; Ficha de especie de Greta oto; HowStuffWorks; Recopilacion sobre el ciclo de Greta oto; Anywhere, ficha Glasswing Butterfly; Ficha de especie de Greta oto (Schulz et al. 2004, Biochemical Systematics and Ecology); Ficha de especie de Greta oto (Henderson 2002); Ficha de especie de Greta oto (Dyer et al.)

Best time: It is migratory: it covers up to 19 km a day at speeds of up to 13 km/h, moving mainly with altitude, which makes its density vary greatly from place to place and moment to moment