Philodromus

Walckenaer, 1826

Running Crab Spiders

Species Guides

29

Philodromus is a large of running crab spiders in the Philodromidae, comprising over 200 described worldwide. Members are characterized by a distinctly flattened body and laterigrade legs—oriented horizontally rather than vertically—that enable sideways movement. Unlike typical crab spiders (Thomisinae), Philodromus species lack heavy bodies and prominent , instead possessing lithe, smooth bodies with slender, nearly equal-length legs. They are active of woody plants and are frequently encountered on vertical surfaces including building walls.

Philodromus rufus by (c) Trevor Van Loon, some rights reserved (CC BY), uploaded by Trevor Van Loon. Used under a CC-BY license.Philodromus laticeps by no rights reserved, uploaded by Lyn Roueche. Used under a CC0 license.Philodromus rufus jenningsi by no rights reserved, uploaded by Trevor Clarke. Used under a CC0 license.

Pronunciation

How to pronounce Philodromus: /fɪloʊˈdroʊməs/

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

Identification

Distinguished from Selenopidae (flatties) by leg proportions: Philodromus has the second pair of legs longest, while Selenopidae have legs increasingly longer from front to back. Distinguished from Thomisinae crab spiders by slender, equal-length legs versus heavy bodies with marked leg disparity, and by smooth bodies lacking prominent . Distinguished from Sparassidae (huntsman spiders) by smaller size and different eye arrangement.

Images

Habitat

Surfaces and crevices of woody plants including trees and shrubs; frequently found on vertical surfaces such as building walls, fences, and tree trunks. Some occupy orchards and agricultural settings.

Distribution

Holarctic distribution predominates, with highest diversity in the Palearctic. Extends into southern regions including parts of Africa, Australia, and northern South America (single P. traviatus). Central Europe approximately sixteen species.

Seasonality

with activity varying by and latitude; some species active year-round in suitable conditions.

Diet

Active capturing small arthropods; prey detected by contact or short-distance vision. Laboratory studies on P. rufus used Drosophila melanogaster as prey. Some rejected as prey.

Life Cycle

with females producing multiple sacs. P. praelustris females produced up to 12 egg sacs containing over 200 eggs total under insectary conditions, though natural appears lower. occurs via bridging—casting air-borne web loops that catch on distant objects—by all life stages; ballooning possible but unconfirmed for very young individuals.

Behavior

Active, that do not build webs for prey capture. Males of some (e.g., P. rufus) vibrate legs during courtship; other species lack this . Prey capture involves direct pursuit or ambush on plant surfaces. At high prey densities, uncaptured prey may interfere with feeding spiders.

Ecological Role

in arboreal and shrub ; contribute to regulation of small insect . to prey demonstrated in laboratory studies.

Human Relevance

Frequently encountered in and around human dwellings, particularly on exterior walls; one of the most common spiders reported from showers and indoor vertical surfaces. Non-dangerous to humans; bites rare and not medically significant. Subject of ecological and behavioral research due to accessible laboratory rearing.

Similar Taxa

  • Selenopidae (flatties)Similar flattened body and laterigrade legs, but distinguished by leg length pattern (increasing from front to back vs. second pair longest in Philodromus) and six in one row
  • Thomisinae (typical crab spiders)Same (Thomisidae) but differs in heavy body, prominent , marked leg length disparity, and slow gait versus Philodromus's lithe build and active movement
  • Sparassidae (huntsman spiders)Similar flattened appearance and wall-dwelling habit, but much larger size, different arrangement, and faster running speed

More Details

Research significance

Philodromus are important model organisms for spider behavioral , with extensive laboratory studies on predatory , , and sexual behavior. P. rufus in particular has been studied for -dependent parameters and mating system evolution.

Taxonomic complexity

The contains cryptic (e.g., P. rufus complex) distinguished by subtle morphological and behavioral differences, particularly male courtship and genitalic structures. Sexual behavior has proven critical for delineation.

Tags

Sources and further reading