False news of an impending insect apocalypse has long been debunked. Insects are not declining globally any faster than everything else. On a drive through Manas NP I took a few photos of the colourful insects that I saw in passing. The bee in the featured photo had beautiful wings of a kind I’d never seen before. Most insect colours are not due to pigments, but due to nanostructures on the wings or chitin, but they are equally tuned by evolution. Some time I need to find more about why and how insects use colour.
Exactly this issue has been studied extensively in butterflies. Bright colours in butterflies and caterpillars signal to predators that they are poisonous. This gives rise to a whole evolutionary chain of cheats: mimics which are not poisonous, but evolve colours which advertise, falsely, that they are. This drab looking butterfly, a blue crow (Euploea mulciber) seems to be an exception, because all crows and tigers are poisonous. But when it opens its wings you can see a deep blue colour in the forewing. Still pretty drab, you may think. But that’s because you are not a bird. Birds have colour receptors for ultraviolet in their eyes, and to them this butterfly would be a dazzling blue, advertising how poisonous it really is.
And then there were the flies. An iridescent blue-green blowfly (family Calliphoridae) landed on our jeep and crawled over the guard rails. I’m sure we’d deposited our sweat on it, and this was busily lapping up the salt. You would expect jungles to be full of blowflies. Their maggots feed on carrion and excrement, and there is no dearth of those in a jungle. The striped black and yellow insect which hovered around us gave me a bit of a scare. I thought it was a wasp and tried to bat it away, until I found that it was a hover fly (family Syrphidae). This nectar drinking pollinator mimics a wasp’s colouration for safety from predators. It wouldn’t work unless there were wasps in the jungle. Although I didn’t see one, the hover fly told us that they must be around. Traveling by jeep through a forest you miss most insects. I was fortunate to have at least caught a few of the more colourful ones.