Explosive backpacks: Termites explode to defend their colonies

From Nature:

TermitesA species of termite found in the rainforests of French Guiana takes altruism seriously: aged workers grow sacks of toxic blue liquid that they explode onto their enemies in an act of suicidal self-sacrifice to help their colonies (see video).

The “explosive backpacks” of Neocapritermes taracua, described in Science today1, grow throughout the lifetimes of the worker termites, filling with blue crystals secreted by a pair of glands on the insects' abdomens. Older workers carry the largest and most toxic backpacks. Those individuals also, not coincidentally, are the least able to forage and tend for the colony: their mandibles become dull and worn as the termites age, because they cannot be sharpened by moulting. “Older individuals are not as effective at foraging and nest maintenance as younger workers,” says Robert Hanus, who studies termite biology at the Institute of Organic Chemistry and Biochemistry in Prague, and led the study. But when the workers are attacked, he says, “they can provide another service to the colony. It makes perfect sense to me because theories predict that social insects should perform low-risk, laborious tasks such as housekeeping in the first part of their life and risky tasks such as defence as they age.”

More here.