Slender crab spider
Tmarus piger
The slender crab spider is a master of ambush, perfectly adapted to life on twigs through its coloration and body shape. A distinctive feature is the cone-shaped tubercle at the posterior end of the abdomen. In a resting position, it extends its long front legs forward to mimic the shape of a small twig. It does not spin webs but overcomes its prey through speed and potent venom.
Details
Identification
Elongated body; characteristic tubercle at the end of the abdomen; brownish-grey camouflage; front pairs of legs significantly longer than the rear.
Social behavior
Solitary living; interactions are largely limited to the mating season; cannibalism is possible.
Diet
Small flying insects, ants, and other tree-dwelling arthropods.
Hunting strategy
Ambush predator; uses camouflage to catch prey from ambush without building a web.
Spawning substrate
Eggs are laid in cocoons on leaves or twigs.
Overwintering
Overwinters as a juvenile (subadult) in the herb layer or under bark.
Ecology
Ecological role
Predator in the trophic structure of bushes and tree canopies; contributes to the control of insect populations.
Natural predators
Birds, ichneumon wasps, larger spiders.
Competitor species
Other crab spider species (e.g., Xysticus spp.) and jumping spiders.
Ecosystem service
Biological pest control through predation of insects.
Threats
Intensification of forestry; removal of dead wood and hedges; large-scale use of pesticides.
Scientific profile
Profile
Distinguishing features
Characteristic is the posteriorly elongated opisthosoma (abdomen), which features a distinct hump (tubercle) at the end. In a resting position, the spider stretches the first two pairs of legs far forward while the rear legs clasp the twig, making it look like a short branch stump.
Habitat
Prefers warm, sunny locations such as forest edges, open deciduous and mixed forests (often on oak or pine), shrublands, orchard meadows, and occasionally bogs or dry grasslands with woody vegetation.
Role in food web
Important predator of small arthropods in the shrub and tree layers; serves as prey for insectivorous birds, parasitic wasps, and larger spiders.
Protection & threats
Main threats
Loss of structurally rich forest edges and semi-dry grasslands due to intensive agriculture or forestry, as well as the removal of deadwood and undergrowth.
Population trend
Stable; in Germany, the species is classified as 'Least Concern' according to the Red List (2016), potentially benefiting regionally from climate warming.