A tortoise among the leaves

Geetha Iyer

A few months ago, I had introduced Ipomoeas to you. If you found the opportunity to observe or study them, it’s quite likely that you may have noticed a pretty colourful beetle scuttling amongst them. Ipomoeas are favourite food plants for insects and so host several of them. Quite a diverse group of insects may be observed on these plants. One to be surely found is a beetle fondly called, ‘the tortoise beetle or tortoise shell beetle’.

aspidimorpha-sp Why are they called tortoise shell beetle? If you can observe them, then this question is easily answered. All insects have two pairs of wings. In beetles, the outer pair of wings or the forewings, called elytra, are not used for flight. They are hard and protect the inner pair of hindwings as well as the body beneath the wings. In tortoise shell beetle, this function is even more comprehensively carried out. The elytra in these beetles are expanded to cover the entire body. The pronotum (the first segment of the thorax) extends similarly over the head. Together these two structures form a protective shield, like a hood for the beetle. When the beetle perceives danger, it quickly withdraws its head, antennae and legs beneath the hood just like a tortoise withdrawing its body under its shell, hence earning the common name.

The expanded covering clamps down so firmly that hunters like ants, which grab their insect prey by the legs will not be able to penetrate the hood. The strong and firm elytra may deceptively appear to be one continuous transparent cover; but they are not. When it starts to fly, what appeared till then as a continuous shield suddenly splits in the middle, revealing the two halves of the wings. The forewings move outwards and upwards, to allow the inner hindwings to spread and fly. Because the elytra are somewhat transparent, the patterns and colours on the body are visible, making it one of the most attractive kinds among beetles.

The author is a consultant for science and environment education. She can be reached at scopsowl@gmail.com.

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