Philodromidae

Thorell, 1870

Running Crab Spiders, Philodromid Crab Spiders

Genus Guides

7

Philodromidae is a of araneomorph spiders comprising over 530 across 31 . Members are commonly called running crab spiders or philodromid crab spiders due to their crab-like appearance and sideways-oriented legs. Unlike true crab spiders (Thomisidae), philodromids do not construct webs for prey capture but instead hunt by ambush. They are primarily associated with vegetation, where they occur on stems, leaves, and tree trunks.

Philodromidae by (c) Wynand Uys, some rights reserved (CC BY), uploaded by Wynand Uys. Used under a CC-BY license.Philodromus laticeps by no rights reserved, uploaded by Lyn Roueche. Used under a CC0 license.Thanatus striatus by (c) quinnm, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Philodromidae: /fɪloʊˈdroʊmɪˌdeɪ/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Philodromids possess laterigrade legs—oriented sideways like those of crabs—with the first two pairs projecting forward. The second leg pair is often longer than the first, most dramatically in the Ebo where it may be twice as long. are arranged in two curved rows with the row wider than the . Scopulae (adhesive hairs) are present only at the tarsal tips, unlike in Sparassidae. Body coloration is typically cream to light brown with faint longitudinal stripes. The overall body form is flattened.

Images

Habitat

Primarily associated with vegetation including grasses, shrubs, tree trunks, low herbage, and undergrowth. Some occur specifically on deciduous trees, others on conifers. A small number inhabit desert environments.

Distribution

Worldwide distribution. Documented from North America (including southern California to western Texas, Florida, and the Caribbean), Europe, Asia (including South Korea, China, Japan), Africa (Afrotropical region), and the Neotropics.

Seasonality

and immatures overwinter in temperate regions, becoming active in early spring when temperatures rise. Peak activity observed from March through May in North American temperate zones.

Diet

Active that hunt by ambush. Prey consists of insects and other small arthropods captured directly without web use.

Life Cycle

Females construct flattened sacs which they guard until spiderlings emerge. occurs as or immatures in leaf litter, grass tussocks, or other sheltered microhabitats. Spiders contain glycerol and specialized proteins in that reduce freezing point, enabling cold .

Behavior

Non-web-building hunters that rely on speed and ambush rather than silk traps. When disturbed, they can sprint with surprising speed. Some are known to enter buildings; the house crab spider (Thanatus) commonly captures flies on and in structures.

Ecological Role

of insects and small arthropods in vegetation . Serve as prey for spider wasps (Pompilidae), including Priocnemis minorata which has been documented parasitizing Thanatus.

Human Relevance

Not dangerously venomous to humans. Occasionally encountered indoors where they may capture pest flies. Frequently mistaken for true crab spiders (Thomisidae) or, in the southwestern U.S. and Florida, for the unrelated 'flatties' (Selenopidae).

Similar Taxa

  • ThomisidaeTrue crab spiders share laterigrade legs and crab-like appearance, but differ in having markedly unequal leg sizes with first two pairs much longer and stouter, and in building no sacs (guarding eggs under silk instead).
  • Selenopidae'Flatties' share extreme flattening and laterigrade legs, but have six in one row (vs. two curved rows in Philodromidae), legs increasingly longer from front to back (vs. second pair longest in Philodromidae), and a notched rear sternum edge.
  • SparassidaeGiant crab spiders may appear similar but have scopulae covering entire rather than just tips, and different arrangement.

Tags

Sources and further reading