February 2022

Masters of disguise

I was photographing a spider when I noticed what I thought was a piece of lichen blowing in the wind, even though I didn't feel any wind. I was surprised when it moved like a looper caterpillar. I thought I would be able to make out a camouflaged caterpillar when I saw it blown up on the computer monitor. I can't. It still looks like lichen to me. I didn't notice the moth next to it until I saw the enlarged image.

Answer

Few predators would expect this pile of lichen to hide a tasty caterpillar. Can you also see the adult moth next to it? Young bizarre looper caterpillars use found materials for camouflage, so their appearance can vary between individuals. Photo: Bruce Cowell, QM. Adult Eucyclodes moths commonly have patterns of green, brown, and grey, often with different markings on males and females. This species is Eucyclodes fascinans. Photo: Jeff Wright, QM.

Your caterpillar is one of the bizarre loopers (a species of Eucyclodes); a caterpillar of a moth.

‘Looper’ is a name given to some moths in the Family Geometridae (as well as a few other groups of moths whose caterpillars move in a similar fashion), as their caterpillars have a distinctive looping gait. They stretch out the front of the body and grab onto the surface before bringing up the rear of the body and placing it just behind the front, so that the middle part of the caterpillar is in a tight loop (this is also the origin of another common name for these caterpillars: “inch-worms”).

Caterpillars make tasty snacks for numerous predators, so they have evolved a variety of defensive adaptations and behaviours. Some are able to accumulate or synthesise toxins, some can suddenly change their appearance (entomologists call this behaviour a “startle display”), and some have stinging spines or irritating hairs. Most caterpillars, however, rely on camouflage for defence. Bizarre loopers take this to an extreme. Young caterpillars camouflage themselves with bits of debris and lichen (as the one in the photo has done). Caterpillars need to shed their skin several times as they grow , and in later moults the bizzare loopers discard the debris and rely on the weird lobes of their own body for camouflage.

As you noticed, the photo contains two well-camouflaged lepidopterans: the bizarre looper caterpillar and an adult moth. The adult moth is no relation to the caterpillar, but it’s so good at hiding its identity that we’re unable to identify it!

Looper caterpillars have featured in the Question of the Month before, in a rather grisly story.

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