Philodromus dispar

Walckenaer, 1826

Eurasian Running Crab Spider

Philodromus dispar is a small running crab to Eurasia that has been to North America. It is an active hunter that does not build webs, instead ambushing on vegetation. The exhibits pronounced in coloration: males are shiny black or dark with margins, while females are highly variable in size and color. Its attachment ability depends on ambient humidity, with optimal adhesion at intermediate humidity levels.

Philodromus dispar by (c) Donald Hobern, some rights reserved (CC BY). Used under a CC-BY license.

Philodromus dispar by (c) gdahlman, some rights reserved (CC BY). Used under a CC-BY license.

Philodromus dispar by (c) Alexis Tinker-Tsavalas, some rights reserved (CC BY), uploaded by Alexis Tinker-Tsavalas. Used under a CC-BY license.

Pronunciation

How to pronounce Philodromus dispar: //ˌfɪloʊˈdroʊməs ˈdɪspɑr//

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

Identification

Distinguished from North Philodromus by its status and specific male coloration (shiny black with edges). Females are difficult to identify due to high variability and require careful examination. Distinguished from the infuscatus group (native to the Americas) by geographic origin and morphological details; P. dispar is the sole American representative of the dispar group. Running crab in general can be separated from true crab spiders (Thomisidae) by their leg orientation and flattened body profile.

Images

Appearance

Small approximately 5 mm in body length. Males are shiny and iridescent black or dark with distinct edges on the and . Females are highly variable in both size and coloration, ranging from light to dark without the consistent patterning seen in males. The possesses hairy attachment pads () on its that enable adhesion to smooth surfaces.

Habitat

and shrub-dwelling; found on trees and bushes. Occupies in both natural and human-modified environments.

Distribution

to Europe, Turkey, the Caucasus, Russia (European part to South Siberia), and Iran. to North America, with established in the United States and Canada. Also recorded from Flanders, Belgium.

Diet

Active of and other small . Does not construct capture webs.

Behavior

Agile, hunter that relies on speed and ambush rather than web-building. Remains stationary on vegetation to await , then pursues it actively. Attachment ability to smooth surfaces varies with humidity: adhesion is strongest at intermediate (approximately 50-70%), weaker in dry conditions, and substantially reduced at high humidity due to water condensation on surfaces.

Ecological Role

in and shrub .

Human Relevance

in North America; subject of biomechanical research on dry adhesion mechanisms. Not known to be of economic or medical importance.

Similar Taxa

Philodromus infuscatus group group comprising 20 species and 2 ; P. dispar is the sole representative of the dispar group in the Americas, distinguished by Old World origin and male coloration

More Details

Biomechanical research significance

P. dispar has been used as a model organism for studying humidity-dependent adhesion in 'dry' adhesive systems. Its attachment operate via van der Waals forces modified by capillary effects at intermediate humidity, with performance declining at both low and high humidity extremes.

Taxonomic note

The dispar group is primarily Palearctic in distribution; P. dispar represents the only member of this group established in the Americas, where it occurs alongside the diverse infuscatus group.