Grass Spider

Agelenopsis pennsylvanica — the grass spider — is one of about 14 species in genus Agelenopsis (the funnel-web grass spiders) and one of the most familiar funnel-web spiders in eastern North America. The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to Texas. Females are 12-19 mm body length (males 9-12 mm), with the species' diagnostic features: tan-brown body with two darker longitudinal stripes running down the cephalothorax (the front body segment), pale undersides, and long legs adapted for fast running. The species' major significance is the SHEET-WEB-AND-FUNNEL HUNTING STRATEGY. Grass spiders construct distinctive WEBS consisting of: (1) a HORIZONTAL SHEET WEB — densely woven sheet of silk that can be 5-30 cm in diameter, typically constructed in tall grass, lawn vegetation, or shrub layers; (2) a TUBULAR FUNNEL RETREAT at one corner of the sheet web — a silk tube extending into the surrounding vegetation where the spider waits between hunting events. The web is NON-STICKY (unlike orb webs which are sticky to ensnare prey) — instead, the dense sheet web functions as a TARGET that prey insects falling from above stumble onto. The spider waits at the rear of the funnel retreat, monitoring the sheet for vibrations from prey landings. When prey is detected, the spider DASHES OUT across the sheet at lightning speed — Agelenopsis sprint speeds reach 60 cm/sec (extraordinary for a spider — most spiders are not capable of sustained running speeds), allowing the spider to seize prey before it can escape. The spider then drags the prey back to the funnel retreat for consumption. Grass spiders are one of the FASTEST RUNNING SPIDERS in North America. The species' fast-running locomotion is also the source of the family Agelenidae's traditional Latin name 'tube-web spiders' (referring to the funnel retreat) and modern English 'funnel-web spiders' (which can cause confusion with the unrelated Sydney funnel-web spider Atrax robustus, which is a deadly Australian spider in family Atracidae despite the similar common name). Grass spiders are essentially harmless to humans (no medically-significant venom, not aggressive — bites are extremely rare and cause only minor local irritation when they do occur) and are major beneficial garden predators of small insects. The species is one of the most-encountered funnel-web spiders in NA backyard natural history — webs are conspicuous in grass and shrub layers in late summer (August-October, when adult Agelenopsis populations peak).