Thomisus onustus Is a Crab Spider species in the genus Thomisus, Family Thomisidae.
Length. Female 6mm to 7 mm. Male 2mm to 4mm.
This species shows sexual dimorphism both in size and coloration.
Colour varies, in the male the prosoma varies from, yellow brown to dark brown the opisthosoma could be yellow, green or brown.
Females are also variable in colour, basic colour can be white, pink, yellow pale brown, sometimes additional shades of red.
This species is characterised by the prominent rear corners of the opisthosoma.
These crab spiders do not make a web, they rely on stealth by assuming the same colour as the flower they are hunting on. (In the images below the female is actually acting as the absent flower on the plant)
The prey consists of flower-visiting insects of all species, hoverflies, bees, wasps, butterflies and beetles. which are often several times larger than the spider. They take their prey with two powerful and highly enlarged pair of front legs, then usually kill the prey by biting on the back of the neck.
Emerging spider lings of Thomisus onustus may feed on pollen or nectar when insect prey is lacking.
Mating usually takes place in June. The male climbs onto the back of the female to copulate. The female during the entire mating is completely passive and does not show any aggressive behaviour towards the male.
Can be found in most of Europe, they prefer warm climates but can be found as far north as Great Britain, but absent in Ireland, also can be found as far east as Japan.
Habitat... forest-free areas, dry, sandy open spaces and dry grasslands bathed in hot sunshine.