Velia caprai, known as the water cricket, is a species of aquatic insect Hemiptera found in Europe. It grows to a length of and is stouter than pond skaters of the family Gerridae. It is distasteful to predatory fish, engages in kleptoparasitism, and can travel at twice its normal speed by spitting on the water surface.
Description
The adult insect grows to a length of .
Members of the family
Veliidae resemble the pond skaters of the family
Gerridae, but with stouter middle and hind legs, and a generally stouter appearance.
Ecology
Velia caprai has a chemical defence mechanism which is often able to prevent predation. It is so distasteful to
brown trout (
Salmo trutta) that the fish will spit out any
Velia caprai it takes without causing them any damage.
Behaviour
Velia caprai is subject to
kleptoparasitism. In one study, whenever it took prey heavier than , other bugs of the same species joined it and successfully ate parts of the prey.
One unusual Behavior exhibited by Velia caprai is called "expansion skating", or Entspannungschwimmen (German language for "relaxation swimming"), in which saliva is ejected from the insect's beak onto the surface of the water, lowering the surface tension and allowing the insect to travel at up to twice its normal speed.
Velia caprai aligns itself to the plane of polarised light, although the reasons for this behaviour are not clear.
Taxonomic history
Velia caprai was first described as a separate species by Livio Tamanini in 1947, in a
revision of the genus
Velia. Formerly,
V. caprai and other species, such as
V. saulii, were included in
Velia currens (Fabricius, 1794).
