Inon Scharf

ScienceShot: Sick Ants Don't Compromise the Whole Nest

A particularly bad flu season can empty schools, clear out offices, and cripple productivity. But when ants are infected—with tapeworms, for example—their nests, surprisingly, keep humming along. The tiny ant Temnothorax nylanderi lives in groups of up to 200 in acorns and sticks in European forests. Parasite eggs likely enter the nest via woodpecker feces, which the ants collect and feed to their young. The young become infected by consuming the eggs with the feces and wind up petite and yellow—instead of brown—as adults (see picture). Researchers have found that up to a third of T. nylanderi's nests are infected, and they expected to see a corresponding productivity decline in those nests. Indeed, a comparative study of sick and healthy ants collected from the wild and kept in artificial glass containers showed that sick ants don't do their share: They rarely go outside the nest and spend most of their time hanging out or begging food from their healthy nestmates. Yet the colony as a whole is as productive as uninfected colonies, researchers reported online today in The American Naturalist. It seems that, despite their industrious reputation, quite a few ants just sit around and do nothing—which means that there's an existing buffer of workers already laboring to make up for the sick ones. But an examination of nests brought in from the wild showed one difference: The infected colonies produced more males than the uninfected ones—possibly because males are more likely to move away from the nest and out of range of the local tapeworm.

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