The creature in the picture is a caterpillar with a pretty weird habit. That bit that looks like a spike is actually a pile of heads. As if that wasn’t odd enough, the heads all once belonged to the same caterpillar.

Caterpillars go through molts as they grow. They start off teeny-tiny, and as they get bigger they split their old, tight skin and emerge in a sparkly new skin, then grow some more. Actually, lots of invertebrates do this, from caterpillars to lobsters. Some eat their old skins, some just leave them lying around. But the gum lead skeletoniser caterpillar keeps the head each time after its fourth molt. As it grows, its pile of heads grows longer, forming something that looks like a spike at the front of the caterpillar.A spike made of old heads – that’s pretty weird.

The dead heads can’t do anything – they are as dead as the hair that has come from your head, or the ends of your fingernails. But it seems they can act as a defensive weapon. Petah Low, a research scientist in Australia set up a contest between two caterpillars, one with a spike of old heads and one without, and a predatory insect called a stinkbug that wanted to eat the caterpillars. The stinkbug has a sharp, needle-like mouth that it uses to inject poison into its prey and then to such out the insides. Nice (not). The caterpillar without its spike of heads was quickly defeated; it took only 14 seconds for the stinkbug to win. The caterpillar with its head-spike held out for 120 seconds, using its spike like a sword or lance, knocking aside the stinkbug’s needle-mouth. But it still lost in the end.

Learn more from this study of gum leaf skeletoniser caterpillars.