How a mind-control virus turns caterpillars into exploding 'zombies'

As if caterpillars didn’t have it hard enough.

Already the insect equivalent of an ugly duckling, caterpillars are also the potential victims of a “zombie” virus that causes them to explode in one of the most horrifying deaths in the animal kingdom.

Chris Miller, a researcher at the Wildlife Trust in Lancashire, England, was doing a butterfly survey when he spotted a dead caterpillar hanging from a leaf, in “an inverted U.”

That’s unusual, Miller said, because a caterpillar is a delicacy for birds in the area. Climbing onto a leaf in the middle of the day is like offering yourself up as lunch. And even in its long-dead state, the insect didn’t look quite right.

“It had started to go a bit mushy, is probably the nicest way of putting it,” Miller said.

Why would a caterpillar go against every survival instinct it had evolved over millennia and march out onto a leaf, in plain sight of predators?

It turns out the caterpillar didn’t have much say in the matter.

A type of virus had taken over the insect and turned it into a single-minded virus-spreading vessel.

The baculovirus halts a caterpillar’s moulting activity, encouraging it to keep eating and get bigger, which creates more of the virus. When the caterpillar is sufficiently massive, the virus alters its climbing activity, forcing it up high onto a leaf.

Right before the caterpillar dies, the virus releases an enzyme that liquefies the insect’s tissue. If the caterpillar is lucky it will be plucked off the leaf by a bird and, if not, its liquid-insides explode, raining down on the other caterpillars and branches below.

If those caterpillars consume the virus, the whole process starts over again...


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