Thanatus formicinus

Thanatus formicinus is sexually dimorphic, although the males and females are similar in colour and pattern the male is markedly smaller than the female with a body length of 5.2mm to 7.4mm compared to the females' body length of 6.9mm to 12mm.^[3] The abdomen is pale brown to greyish brown with a clear, white margined rhomboidal mark and there may be two slender, arced black lines at the rear. The carapace is similar in colour to the abdomen but with a light central band. The legs and palps are aso a similar colour to the abdomen although there are few black spots on the legs. The males resemble the females in colour and markings although they are typically darker.^[4]

Thanatus formicinus has a Holarctic distribution and is found in North America, Europe and Asia, as far east as Japan, it also occurs in Iraq, Iran, Turkey and North Africa. It has been introduced to Svalbard.^[3] In the United Kingdom the diamondback spider has always been rare and was known from three sites in southern England before 1969 but was not recorded after then until a population was discovered in Clumber Park in Nottinghamshire in 2017.^[5] This species is generally found in dry and semi-dry meadows and warm, dry forest steppes.^[3] In Britain it is found in bogs dominated by sphagnum with Molinia caerulea and some heather.^[6]