Agelenopsis aperta

(Gertsch, 1934)

Desert Grass Spider, Funnel-web Spider

Agelenopsis aperta, commonly known as the desert grass spider, is a medium-sized funnel-web weaver native to arid regions of the southwestern United States and northwestern Mexico. It constructs characteristic non-sticky funnel-shaped webs in crevices and vegetation, where it waits to ambush prey. The exhibits notable territorial and complex courtship rituals involving abdominal swaying and release that induces a temporary cataplectic state in females.

Agelenopsis aperta by no rights reserved, uploaded by Jesse Rorabaugh. Used under a CC0 license.

Agelenopsis aperta 2304309 by Juan Cruzado Cortés. Used under a CC BY-SA 4.0 license.

Agelenopsis aperta 2180679 by Juan Cruzado Cortés. Used under a CC BY-SA 4.0 license.

Pronunciation

How to pronounce Agelenopsis aperta: /əˌd͡ʒɛlɪˈnɒpsɪs əˈpɜːrtə/

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

Identification

Distinguished from other Agelenopsis by geographic range (desert Southwest). Long held parallel distinguish it from Hololena (short, inward-directed spinnerets). The two dark stripes on pale and two black stripes on tan are characteristic of funnel-web weavers generally. Mature males wander and may enter buildings; females remain with webs.

Images

Appearance

Body length 13–18 mm (females larger than males). tan to gray with two longitudinal brown stripes. tan with two black stripes. Legs relatively long, annulated with alternating light and dark bands. prominent, long, and extend posteriorly from abdomen. Eight arranged in two rows forming an arc. Overall coloration gray, brown, and black.

Habitat

Dry and arid regions including desert grassland, lava beds, rangeland, and shrubland. Webs constructed in crevices between rocks, on bushes, in tall grass patches, or in building corners. In grasslands: placed in tall grass patches. In lava beds: associated with shrubs or depressions at lava bed outskirts. Occasionally found indoors in undisturbed corners.

Distribution

Southwestern United States (southern California to Texas) and northwestern Mexico.

Seasonality

Active year-round in suitable conditions; most active at night for foraging. Mature males wander seeking females into fall (observed into late October).

Diet

Insects captured on webs, primarily grassland insects including grasshoppers and aphids; also other spiders. Prey captured on flat web surface, then dragged into funnel for feeding.

Life Cycle

Spiderlings initially occupy a communal web, then disperse to build individual webs nearby. Spiderlings exhibit competitive over food resources.

Behavior

hunting activity. Constructs non-sticky funnel-shaped webs with sheet platform and tubular retreat; waits in tube sensing vibrations, then rapidly emerges to capture prey. Can escape through bottom funnel opening if web damaged. Territorial: defends web sites against intruders through agonistic interactions; more combative individuals maintain larger territories. Courtship involves male abdominal swaying, web flexing, and release inducing female cataplexis (temporary paralysis).

Ecological Role

of insects and other spiders in arid grassland . Contributes to nutrient cycling through prey consumption. Serves as prey for birds, particularly in woodland where risk is higher.

Human Relevance

Bites to humans considered generally harmless and not medically significant, though a few cases in Southern California reported (headache, weakness, disorientation, pallor, lethargy). Venom contains agatoxins (omega-agatoxin IVA and IVB) that block calcium channels; extensively researched for neurobiological applications. Occasionally enters buildings but does not establish indoor .

Similar Taxa

Hololena spp.Also funnel-web weavers in western North America; distinguished by short directed inward vs. long parallel spinnerets in Agelenopsis
Agelenopsis pennsylvanicaEastern grass spider with overlapping ; distinguished by geographic range (eastern vs. southwestern North America)
Eratigena agrestis (hobo spider)Close relative with similar web structure; distinguished by geographic range and slightly different abdominal patterning

Misconceptions

Despite 'funnel-web spider,' it is not related to the medically significant Australian funnel-web spiders ( Atractaspididae/Atracidae). Bites are generally harmless to humans, contrary to concerns based on venom research applications.

More Details

Low-temperature tolerance

Can withstand very low temperatures without cold hardening; likely compensates by moving to protected microhabitats during extreme cold periods.

Web site quality and fitness

Spiders occupying optimal web sites (prey-rich, thermally favorable) achieve larger body size and higher relative ; site quality is a major determinant of individual success.

Habitat selection trade-offs

Laboratory studies show individuals prioritize either preferred temperature range or prey availability when both cannot be satisfied simultaneously, rather than compromising on both.