American Grass Spider
Agelenopsis pennsylvanica
Agelenidae (Funnel-Weavers), Order Araneae
Physical Description
The spider features a robust, elongated body with a brownish cephalothorax marked by distinct longitudinal dark stripes, and a patterned abdomen tapering toward the rear. While the spider itself is not prominently visible in the center of the sheet web shown, typical members of this genus have hairy bodies and prominent, elongated spinnerets extending from the rear of the abdomen.
Size Estimate
Body length typically ranges from 10 to 18 millimeters for females, with a leg span extending up to 3 to 4 centimeters. Specimens vary from juveniles to mature adults depending on the seasonal timing.
Coloration & Markings
Characterized by earthy tones of brown, tan, and grey. The cephalothorax features two dark parallel bands running longitudinally, and the abdomen usually displays a mottled pattern with a lighter median band bordered by darker areas.
Web Type
Builds a characteristic horizontal sheet web with a funnel-shaped retreat at one edge, constructed low to the ground amongst dense vegetation, grass, or evergreen shrubs like the juniper shown in the image.
Eye Arrangement
Eight eyes arranged in two slightly curved rows of four, spread across the anterior portion of the cephalothorax, typical of the Agelenidae family.
Leg Characteristics
Long, tapering legs covered in numerous spines and hairs, adapted for rapid sprinting across the non-sticky sheet web rather than climbing vertical surfaces.
Venom & Safety Information
Venom Information
Possesses mild, non-lethal neurotoxic venom intended solely to immobilize small insect prey quickly.
Medical Significance
Harmless to humans. While capable of biting if firmly pressed against the skin, the bite is typically minor, causing only temporary local irritation similar to a mild ant sting, and lacks medical significance.
Safety Recommendations
No special safety measures required as these spiders are timid and harmless. Simply enjoy observing them from a safe distance or gently relocate using a container if found indoors.
Habitat & Behavior
Habitat & Range
Found across North America in lawns, meadows, gardens, and low-lying shrubs or dense foliage, preferring open, sunny areas where vegetation provides structural support for webs.
Behavior & Temperament
Extremely fast and skittish. They spend most of their time hidden inside the funnel retreat, darting out rapidly across the sheet web to capture prey when vibrations are detected, and retreating quickly when disturbed.
Diet & Prey
Feeds primarily on crawling and flying insects such as grasshoppers, beetles, flies, and moths that happen to land or walk across the non-sticky horizontal sheet web.
Seasonal Activity
Most active and visible during the late summer and autumn months when adults reach maximum size and webs become expansive.
Description
This image highlights the classic architecture of a funnel-weaver's domain: a dense, horizontal sheet web spun intricately among the green foliage of a shrub, complete with a retreat tunnel leading out of sight. Although the resident grass spider remains hidden within its funnel, these webs are a common and fascinating sight in gardens during late summer, showcasing expert engineering designed for rapid ambush predation.
Key Features
Horizontal sheet web terminating in a distinct funnel retreat, elongated posterior spinnerets, and longitudinal stripes on the cephalothorax.
Similar Species
Wolf spiders (Lycosidae) which do not build sheet webs, and purse-web spiders (Atypidae). Labyrinth spiders (Agelena labyrinthica) are similar in Europe.
Life Cycle
Females construct disc-shaped silken egg sacs in protected crevices or near the web site in late autumn. Spiderlings emerge in spring, undergoing multiple molts to reach maturity by late summer.
Ecological Importance
Serves as an effective natural predator of garden insect populations, helping regulate pest numbers while forming an important food source for birds and small mammals.
Conservation Status
Not evaluated by the IUCN, but populations are widespread, stable, and abundant across their natural range.
Interesting Facts
Grass spiders possess some of the fastest acceleration rates among terrestrial invertebrates when sprinting across their webs to secure prey.
Photography Tips
Photograph sheet webs in the early morning when dew highlights the fine silk threads. Use a macro lens focused near the opening of the funnel to capture the spider if it emerges.
Identified: 2026-10-02T12:36:30.573581