Samplings: October 2009

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Joe Sharkey

Bees, ants, and other social insects recognize and cart away their dead. That way, disease does not spread to the whole colony. Other insects, such as cockroaches, simply give their dead a wide berth, probably for a similar reason. Compounds emitted by the corpses—mostly oleic acid and linoleic acid—are the dead giveaways. New research shows that those compounds’ role as pheromones of death, or “necromones,” may be ancient: wood lice (a.k.a. pill bugs or sow bugs), small terrestrial isopod crustaceans whose ancestors diverged from the insect lineage 420 million years ago, also respond to them.

A team composed of student Matthew Yao, his advisers C. David Rollo and Jack M. Rosenfeld, and three others at McMaster University in Hamilton, Ontario, offered the little crustaceans shelters tainted with the crushed bodies of other wood lice, or with solutions of oleic or linoleic acid. The woodlice steadfastly shunned those shelters. That’s evidence of either an amazing convergence between isopods and insects or, more likely, a common response that goes back to the evolutionary ancestor of both groups.

In an interesting aside, the team also showed that tent caterpillars, those pesky defoliators of trees, steer clear of leafy branches swabbed with oleic or linoleic acid—perhaps providing a clue to a new control method. (Evolutionary Biology)