A few years ago I drew a series of insects in what I call my ‘Bugs and Birthstones’ series. Each birthstone is paired with an insect or arachnid of similar colour, all drawn with coloured pencils. I’m pretty proud of the results and you can view the full series here, but the point of this is that I thought I’d write some blog posts on some of the bugs I drew for the Bugs and Birthstones series. I’m going to start today by writing about April’s insect, the glasswing butterfly!
Glasswing butterflies are stunningly beautiful insects, and are very aptly named. Their most distinctive feature is their transparent wings, which are designed to help glasswing butterflies camouflage. While many animals camouflage by having colouration similar to their habitats, glasswing butterflies take this a step further and just go for invisibility. They haven’t quite figured out total invisibility yet, as they do have dark brown around the edges of their wings, as well as a solid brown body.
The structure of glasswing butterfly wings is quite complex, as the wings need to be strong enough to carry the butterfly in flight (they are actually quite strong, glasswing butterflies can carry up to 40 times their own weight), flexible enough for flight, and of course, see-through. I won’t go into the technicalities of their design, but the wings are essentially composed of very, very small ‘nanopillars’, that help prevent absorption of visible light, and creates low scattering and low reflection of light, which combined give the wings their transparent properties.
Though their wings are their most visible (or not) feature, they aren’t the only cool things about glasswing butterflies. Found in Central and South America, glasswing butterflies undergo fairly long migrations, changing elevations as needed. They can fly at speeds of up to 13 km/hr, travelling 19 km a day. This may not sound like a whole lot, but for a butterfly with a wingspan of 5-6 cm, that’s pretty impressive.
In case being (mostly) invisible wasn’t enough, glasswing butterflies have another level of protection from predators. Both caterpillars and adult butterflies feed on toxic plants, the caterpillars on Cestrum, or nightshade plants, and adults on Lantana and Asteracaeae plants. The toxins from the plants make glasswing butterflies taste nasty, so most predators leave them alone.
Mating in glasswing butterflies is a busy affair, with males gathering together in groups called leks to display for females. While they’re all gathered, the male butterflies make sure females notice them by secreting pheromones. After all, there’s no point in performing an elaborate mating display if no one’s there to watch it!
Although there are some flashier butterflies out there with orange and blue and yellow and all kinds of wonderful colours, you have to admit glasswing butterflies have their own kind of beauty. After all, glasswing butterflies can be any colour if they perch in front of the right background!