Higher temperatures could trigger an uptick in damselfly cannibalism

A warmer climate could put some damselflies in distress, as others get bigger and hungrier.

Because of differences in hatching time, nymphs — the immature form of the insects — vary in size. Sometimes when ponds are overcrowded, other food options are scarce or size differences are significant, bigger, older nymphs nosh on the little nymphs. While temperature doesn’t typically affect when damselflies hatch, it does affect how fast they grow.

So a team at the University of Toronto tested whether a warmer world would also be a damselfly-eat-damselfly one. Using damselfly nymphs (Lestes congener) hatched in the lab, researchers put nymphs of various sizes in two different temperature environments, one a balmy 18° Celsius and the other a toastier 24° Celsius.

Damselflies in the hotter setting displayed bigger differences in body size, higher activity levels and increased cannibalism rates. Both size extremes and more frequent foraging probably contribute to the increase in intraspecific dining tendencies, the researchers write May 16 in Biology Letters.