For Your Eyes Only!

Caterpillars of moths and butterflies, due to their very vulnerable disposition, are known to take remarkable anti-predatory measures. During the early stages of instar (a phase between two consecutive periods of molting) the caterpillars, due to their diminutive size, can blend in with the host plant by hiding and through camouflage. However, as they continue to grow in size, their ability to remain concealed takes a serious downturn. It is mostly during the fifth (and last) instar that the caterpillars take offensive measures and rather than hiding, display conspicuous and striking markings to deter predators.

A case in point is the Caterpillar of the Common Mormon butterfly (Papilio polytes). During the first 4 instars this caterpillar, with its brown and white blotched appearance, camouflages itself to resemble bird droppings. However, as it enters its Fifth Instar (seen in the pictures here) it develops a bright green body with two eye-like markings, known as eyespots. These eyespots imitate the eyes of the predator’s enemies and combined with a tapering anterior portion give it the appearance of a snake’s head which stuns the predator.

This is not all – the caterpillar has another ace up its, well, prothorax! Hidden here lies a defence organ known as an osmeterium, which actually looks like the forked tongue of a snake. When disturbed by a predator the caterpillar everts it to give itself an even more convincing snake-like appearance. The osmeterium also releases secretions which have an obnoxious and unpleasant odour that can repel small predators.

A small example of how nature has endowed her children, however vulnerable, with every opportunity to protect and propagate!

– Narendra Nayak © 2018


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