American Grass Spider
Agelenopsis pennsylvanica
Agelenidae (Funnel-Weavers), Order Araneae. Key family characteristics include three pairs of spinnerets with the posterior pair being notably elongated, and the construction of sheet webs ending in a retreat tube.
Physical Description
Elongated body shape with a distinct pattern of longitudinal stripes on the carapace. The abdomen is oval, brownish-gray, and covered in fine setae. Prominent spinnerets are often visible extending from the rear of the abdomen.
Size Estimate
Body length ranges from 10 to 18 mm for females, slightly smaller for males, with a total leg span reaching up to 30 to 50 mm.
Coloration & Markings
Carapace features two dark brown longitudinal bands running parallel on a yellowish-brown or tan background. The abdomen has a central light-colored band bordered by darker, mottled brown or gray areas.
Web Type
Builds a characteristic horizontal sheet web made of non-sticky silk that ends in a funnel-shaped retreat, usually constructed in grass, low vegetation, or structural corners near ground level.
Eye Arrangement
Eight eyes arranged in two slightly curved horizontal rows, all relatively similar in size, typical of funnel-web weavers.
Leg Characteristics
Long, slender legs with distinct dark banding and numerous prominent spines used for tactile sensation and defense.
Venom & Safety Information
Venom Information
Contains neurotoxic venom designed to quickly immobilize small invertebrate prey. It is not considered toxic to humans.
Medical Significance
Harmless to humans. While they possess large enough fangs to occasionally break skin if severely provoked, bites are extremely rare, non-medically significant, and produce only mild, short-lived local irritation comparable to a mosquito bite.
Safety Recommendations
No special safety measures are required. If one enters the home, simply guide it into a container using a piece of paper and release it outdoors.
Habitat & Behavior
Habitat & Range
Found across North America, typically inhabiting grassy fields, lawns, gardens, and the exterior walls or foundations of human dwellings.
Behavior & Temperament
Extremely fast runners and notoriously skittish. They spend most of their time hidden inside their funnel retreat, darting out rapidly to capture prey that lands on the sheet web.
Diet & Prey
Generalist predators feeding on various ground-dwelling insects including grasshoppers, beetles, flies, and ants.
Seasonal Activity
Most active and noticeable during late summer and autumn when mature males wander in search of mates and females produce egg sacs.
Description
The American Grass Spider is a common and fascinating sight around human habitations, particularly in late summer and autumn. Known for building extensive sheet webs over lawns and house foundations, this speedy hunter spends its life waiting near a silk funnel. Despite their sometimes startling speed and wolf-spider-like appearance, they are entirely harmless and beneficial neighbors.
Key Features
Prominent, elongated posterior spinnerets, two dark parallel stripes running down the cephalothorax, and the signature sheet-and-funnel web structure.
Similar Species
Wolf Spiders (Family Lycosidae), which do not build webs and lack the elongated spinnerets, and Hobo Spiders (Eratigena agrestis), which possess more uniform coloration without distinct carapace stripes.
Life Cycle
Females construct tough, disc-shaped silk egg sacs in sheltered locations during autumn, where eggs overwinter before hatching into spiderlings in the spring. They have an annual life cycle culminating in the death of adults by late autumn.
Ecological Importance
Act as important natural controllers of insect populations in gardens and around homes, serving as a primary food source for birds and small mammals.
Conservation Status
Not evaluated by the IUCN, but populations are secure, abundant, and widespread throughout their natural range.
Interesting Facts
Grass spiders possess some of the fastest acceleration rates among terrestrial animals when lunging from their funnel retreats to capture prey.
Photography Tips
Use a macro lens with a fast shutter speed to capture the spider when it pauses near its funnel entrance, utilizing natural side-lighting to highlight the carapace stripes.
User Notes
Found on side of the house
Identified: 2026-08-04T00:31:26.172840