notes

Whirligig beetles are an ancient group of

Adephaga, with reliable fossils going back

to at least the early Jurassic period, almost

200 million years ago. It seems they were

more species-rich and diverse in the past

than now. Adults and larvae have been

found preserved in stone fossils and amber

from countries including Russia, Mongolia,

Burma, Switzerland, and Germany, and

most of these closely resemble the genera

and species living today

but in fact the upper and lower halves are united

within the beetle’s head. Their divided vision,

combined with their incessant frenzied movement,

seems to protect them from being eaten by birds and

fish, and as soon as one of them senses a threat, such

as a shadow passing overhead, they all speed up their

above | Gyrinus A larva with prey.

The structures along the sides are gills

for extracting oxygen from the water.

right | Dineutus An adult North

American Dineutus on land, preparing

for flight. Adults fly well between

potential feeding and breeding ponds.

gyrations, or simultaneously dive to safety. This

makes them very difficult to catch. They have small,

paddlelike hind and middle legs, adapted for rapid

swimming and changing direction. The predatory

larvae live in the water, leaving only to pupate on

emerging water-plant stems in the soil of the banks.