Poisonous setae on a Baltic amber caterpillar.

ABSTRACT

The knobbed setae on a small caterpillar in 45-55 million years old [Eocene] Baltic amber were studied and characterized as urticating, with evidence of liquid release implying the production of poisons. It is presumed that the caterpillar had been disturbed just prior to falling into the resin, as some of its setae showed defensive responses. The swollen tips of the setae are equipped with "trip hairs" and when disturbed, the tips release liquid deposits, some of which contain rod-like bodies. These setal responses to a disturbance are the first report of poisonous setal defense mechanisms in a fossil insect.