The unique web of grass spiders is more often noticed than the spider itself. The web is sheetlike, usually positioned horizontally, with a funnel leading downward to a shelter (a rock crevice or dense vegetation). Though it is typically smaller, the sheet may be up to 3 feet wide and the funnel portion over a foot long.
Grass spiders have a pair of broad, dark, brownish bands running lengthwise adjacent to a lighter middle band on the lightly haired and roundish carapace (head). The legs are cream and dark yellowish brown. The abdomen is oblong, brown, with a broad, reddish-brown, zigzag stripe with a cream-colored border on both sides. The spinnerets, at the hind end of the abdomen, are noticeably long.
There are 14 species in genus Agelenopsis in North America north of Mexico. Three common species in Missouri are:
- eastern funnelweb spider (Agelenopsis naevia
- Pennsylvania funnelweb spider (A. pennsylvanica)
- Emerton’s funnelweb spider (A. emertoni)
Their similar color patterns make them difficult to distinguish. Experts use microscopes to examine small details of their anatomy to identify them to species.
Length: females about ½ to ¾ inch (not including legs); males are slightly smaller.
Statewide.
Habitat and Conservation
These spiders typically build webs several inches above the ground in short grasses and in the window wells of outbuildings. They are common in lawns. Sometimes there can be dozens of sheet webs in a small area. They are especially conspicuous in the morning when covered with dew.
Grass spiders hide in the concealed area of the funnel and then dash out onto the sheet portion of the web to capture an insect caught in or walking across the silken platform. When frightened, they quickly dash into the funnel for safety.
Food
Beetles, harvestmen, moths, and small butterflies are frequent food items. Flying insects first collide with a network of "barrier" webbing above the horizontal sheet web; then the insects fall onto the sheet below. The sheet is not sticky, but insect feet become ensnared by its meshlike strands.
Grass spiders wait at the mouth of their funnel for an insect to land on the sheet of webbing. They dart quickly from the funnel and must quickly decide whether a vibration on the web is a food item, a fallen leaf, or something dangerous to be hidden from. If she's lucky and it's food, the spider delivers a venomous bite to subdue her prey, then carries it into the funnel to be eaten in safety.
Life Cycle
As a general rule, spiders emerge from egg sacs in spring and spend the growing season eating, maturing, mating, and laying eggs. Females continue creating egg cases as long as the weather holds out. As temperatures cool in fall, their metabolism slows, and they generally die when it freezes. Egg cases overwinter, and spiderlings hatch in spring.
Human Connections
Spiders prey on numerous insects that are pests to humans. The web of grass spiders is not sticky, and it can be amusing to tap gently with a twig on the surface of the web, prompting the spider to rush out of her tunnel. She quickly realizes she's been duped and dashes back into hiding.
Ecosystem Connections
These little hunters help control the populations of the many species they consume. Meanwhile, they, and their eggs and young, often are eaten by other predators. The funnel not only enables these spiders to surprise their prey, but also helps them hide from their many predators.
Hummingbirds, kingkets, gnatcatchers, warblers, and vireos collect spider webs and use them in nest building.
