Caterpillar master of camouflage

I WAS taking a break from weeding while sitting in a chair in the garden. Beside this chair was a table and on it were a few dead leaves.

The leaves were small, yellow and oval in shape and suddenly one of them started to move. There was no breeze. I inspected the leaf more closely and it turned out to be a moth which flew away before I could register all the details. I did a bit of checking afterwards and it was probably a species called the common wainscot. It was certainly a fine example of how butterflies and moths have perfected the art of camouflage.

Caterpillars are more susceptible to being eaten than winged insects — some of them form the staple diet of many species of small bird during the breeding season. So caterpillars are the ultimate camouflage experts.

Looper or stick caterpillars not only look like twigs or stems but hold themselves at an angle from the main stem in such a way they are almost impossible to detect until they move. Even fine details such as small buds and leaf scars are simulated and the space between the claspers which grip the stem is often furnished with fine hairs which break up any shadow cast by the body and make the joint between insect and plant invisible.

There are other caterpillars and adult moths that conceal themselves from birds by imitating the droppings of the bird. The Chinese character moth (Cilix glaucata) is a good example, as is the alder moth (Acronicta alni), and the comma butterfly (Polygonia c-album) employs a similar trick.

Caterpillars of the large emperor moth (Saturnia pavonia) feed on heather. When they are small they are black to blend in with the heather stalks. But they soon get too big for this to work convincingly. They then take on a broken green and black pattern which blends perfectly with the foliage of the heather. Caterpillars that feed on pine needles, are almost invariably patterned in longditudinal stripes of green yellow and white to camouflage them. Some species can even vary their camouflage to suit their environment. Many adult butterflies and moths are patterned to blend in with the bark of trees. A species called the peppered moth (Biston betularia) is whitish with a fine peppering of black and blends in perfectly on pale tree trunks speckled with lichen. But when it’s found in industrialised locations where there is no lichen, and soot darkens the tree trunks the commonest form of this moth is almost black all over.

I’ve come to the conclusion serious study of the lepidoptera should be restricted to naturalists who have better eyesight than I do.


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