American Grass Spider
Agelenopsis pennsylvanica
Agelenidae (Funnel-Weavers), Order Araneae. Key family characteristics include three pairs of spinnerets with the posterior pair notably elongated, and an asymmetrical eye arrangement consisting of eight eyes in two rows.
Physical Description
Elongated body with a distinctively tapered, pointed abdomen featuring prominent, visible spinnerets protruding from the rear. The cephalothorax is oblong with characteristic dark longitudinal bands running parallel down the dorsal side.
Size Estimate
Body length is approximately 10 to 15 mm, with a total leg span reaching up to 30 to 40 mm. This specimen appears to be a mature or sub-adult grass spider.
Coloration & Markings
Predominantly brown and tan with contrasting patterns. The cephalothorax features two dark brown lateral stripes flanking a lighter median band. The abdomen displays a mottled brown and gray pattern bordered by lighter yellowish or tan stripes along the edges.
Web Type
Builds a sheet web that is flat or slightly funnel-shaped, constructed close to the ground in grass, low shrubs, or occasionally near structural foundations. The web features a tubular retreat at one end where the spider hides, waiting for prey to strike the horizontal sheet.
Eye Arrangement
Eight eyes arranged in two slightly curved rows of four. The eyes are generally equal in size and positioned closely together across the front of the cephalothorax.
Leg Characteristics
Long, slender legs covered in visible spines and fine hairs. The legs lack specialized banding in most instances, though minor dark spotting may be present, and are held sprawling flat against surfaces or the web when resting.
Venom & Safety Information
Venom Information
Neurotoxic venom used primarily to rapidly paralyze and immobilize insect prey. The venom is relatively weak and has minimal to no effect on humans.
Medical Significance
Not medically significant. Grass spiders are harmless to humans. Their chelicerae are often too small or weak to easily pierce human skin, and a bite typically results in minor, localized irritation comparable to a mild mosquito bite.
Safety Recommendations
No special precautions needed. If found in a sink or bathtub, simply use a cup and a piece of paper to gently scoop the spider up and release it outdoors in a sheltered garden area.
Habitat & Behavior
Habitat & Range
Found widely across North America, from southern Canada down through the eastern and central United States, including Maryland. Preferred natural habitats include lawns, fields, meadows, and gardens; occasionally wanders indoors, especially in autumn when seeking shelter.
Behavior & Temperament
Extremely fast runners when outside the web. They are generally timid, non-aggressive, and will quickly dart into their funnel retreat or scurry away when disturbed rather than bite.
Diet & Prey
Carnivorous. Feeds primarily on ground-dwelling insects such as grasshoppers, crickets, flies, beetles, and moths that land upon or walk across the horizontal sheet web.
Seasonal Activity
Active primarily from spring through late autumn. Peak visibility occurs in late summer and early autumn when webs become dense and adults reach maximum size. Overwinters in the egg stage.
Description
The American Grass Spider is a common and fascinating backyard resident. Often noticed in autumn as morning dew highlights their intricate sheet webs covering lawns, these agile hunters spend most of their lives darting across silken platforms. Though occasionally finding their way into sinks or basements when seeking warmth as temperatures drop, they pose no threat to humans and serve as diligent pest controllers.
Key Features
Prominent, elongated spinnerets at the rear of the abdomen, distinct dark longitudinal stripes running down the carapace, and the construction of a flat sheet web ending in a funnel-shaped retreat.
Similar Species
Wolf spiders (Lycosidae) and nursery web spiders (Pisauridae). Wolf spiders can be distinguished by the lack of prominent, protruding spinnerets and different eye arrangements (prominent large posterior eyes).
Life Cycle
Mating occurs in late summer and early autumn. Females construct disc-shaped silken egg sacs in protected crevices or under debris, where eggs overwinter until hatching in the spring. Spidersheds exoskeleton multiple times before reaching maturity within a single year.
Ecological Importance
Acts as an effective natural regulator of insect populations in gardens, lawns, and agricultural fields, serving as an important link in local food webs as both predator and prey.
Conservation Status
Not evaluated by the IUCN, but populations are secure, highly abundant, and resilient to common environmental disturbances.
Interesting Facts
Grass spiders possess some of the fastest acceleration speeds among terrestrial arthropods when lunging at prey, and their hydraulic leg extension allows them to burst into rapid motion instantly.
Photography Tips
Use a macro lens at a safe, low angle to capture the prominent spinnerets and eye arrangement. Early morning is ideal when dew coats the web or when cooler temperatures temporarily slow down active movement.
User Notes
Found in my kitchen sink this morning in Silver Spring, Maryland in early October
Identified: 2026-10-03T15:07:20.968132