Читать книгу Extreme Insects - Richard Jones - Страница 27

NAME	giraffe-necked weevil Trachelophorus giraffa
LOCATION	Madagascar
ATTRIBUTE	the longest head of any insect

It will come as no surprise to discover that some males have big heads. Big heads can be attached to big jaws (see page 60) or house big eyes (see page 56). But the male giraffe-necked weevil of Madagascar has the most awkward-looking head imaginable. And what does he use it for? Nodding.

The male’s long, slender head takes up about 10 of his 25 mm (1 in) length. The neck is another 7 mm, making the insect’s head and neck over 70 per cent of its entire body length. It holds them angled up from its squat body, like a miniature construction site crane. The female’s head and neck are also relatively long, but only about half her total body length.

The male uses his stretched form for no practical purpose. The nodding, however, is very important to other giraffe-necked weevils. It seems that the males contest one another, trying to out-nod their opponents in ritualised fights. After head-to-head nodding competitions, one male will retreat. It also appears that the females choose the best nodders with which to mate. Thus, over evolutionary time, the males with the longest heads (better for nodding) have been selected.

The irony is that it is the female who really needs a long head. Trachelophorus belongs to a group of beetles called leaf-rolling weevils. She chews through both sides of a leaf blade to the mid-rib. The leaf now has a tendency to curl, a property that she harnesses using her angled neck and head to roll the partly severed plant into a small cigar. She lays an egg inside, and the grub is protected from predators and parasites while it feeds.