Desert Grass Spider, Funnel Weaver
Agelenopsis aperta
Agelenidae (Funnel Web Weavers), Order Araneae. Key family characteristics include long spinnerets and a distinctive funnel-shaped retreat leading from a flat, non-sticky sheet web.
Physical Description
Elongated body with a brownish carapace featuring distinct lateral stripes, and an elongated oval abdomen. Prominent, elongated posterior spinnerets are clearly visible extending from the rear of the abdomen.
Size Estimate
Body length approximately 10 to 20 mm, with a leg span reaching up to 40 to 50 mm, typical for an adult female specimen.
Coloration & Markings
Dull brown or tan coloration with two dark longitudinal bands running along the dorsal side of the cephalothorax. The abdomen features a mottled brownish pattern, sometimes with a lighter median stripe.
Web Type
Funnel web featuring a large, flat, horizontal sheet of non-sticky silk that terminates in a tubular retreat where the spider waits for prey.
Eye Arrangement
Eight small eyes arranged in two slightly curved horizontal rows across the front of the cephalothorax, typical of the Agelenidae family.
Leg Characteristics
Long, tapering legs covered in fine hairs and prominent spines, held in a sprawling posture ready for rapid movement.
Venom & Safety Information
Venom Information
Neurotoxic venom tailored for immobilizing insect prey. It is not considered medically significant to humans.
Medical Significance
Harmless to humans. A bite may cause minor local irritation or pain similar to a mild bee sting, but envenomations are rare as they prefer to flee.
Safety Recommendations
No special precautions needed beyond wearing gloves when clearing old webs from window screens or garden debris to avoid accidental bites.
Habitat & Behavior
Habitat & Range
Found across western North America, typically in grasslands, deserts, and around human structures such as window screens, porches, and foundations where vegetation provides anchor points.
Behavior & Temperament
Highly alert and exceptionally fast runners. They retreat instantly into their silk funnel when disturbed, and generally avoid confrontation.
Diet & Prey
Insects and other arthropods that land on the horizontal sheet web, which the spider rushes out to capture before dragging back to the funnel.
Seasonal Activity
Most active during late summer and autumn when mature adults build their webs and seek mates before temperatures drop.
Description
A classic backyard resident, the funnel weaver constructs intricate sheet webs that span corners, bushes, and window screens. Blending natural camouflage with blinding speed, this spider is a master of ambush on its silken platform, serving as an effective natural pest controller around homes.
Key Features
Prominent, elongated posterior spinnerets; distinctive funnel-shaped retreat; flat non-sticky sheet web; longitudinal stripes on the carapace.
Similar Species
Wolf spiders (Lycosidae), which do not build webs and lack elongated spinnerets, and house spiders (Tegenaria/Eratigena species) which build similar funnel webs but inhabit different indoor ranges.
Life Cycle
Females construct silk egg sacs in protected crevices near the web during autumn. Spiderlings emerge in spring, undergoing multiple molts to reach maturity by late summer.
Ecological Importance
Acts as an important predator of garden pests, helping to naturally regulate populations of flies, beetles, and grasshoppers.
Conservation Status
Not evaluated by the IUCN, but populations are secure, widespread, and highly adaptable to human-modified environments.
Interesting Facts
Grass spiders possess some of the fastest acceleration rates among terrestrial invertebrates when lunging toward prey on their webs.
Photography Tips
Use a macro lens with a fast shutter speed to capture the spider near the mouth of its funnel, utilizing natural side lighting to highlight the spinnerets and carapace stripes.
Identified: 2026-09-03T16:23:11.290396