Grass Spiders
( Agelenopsis sp. )



Identification:Agelenopsis sp.
(Giebel, 1869)
Common Name:Grass Spiders
Life Stage:(A) adult


Taxon Code:ARA01527

Location Name
Redwood Regional Park, Redwood Regional Park, Redwood Regional Park, EBRPD, 7867 Redwood Rd, Oakland
County:Alameda County
ECI Site#:CAEB450001
Park/Forest Code:Redwood Regional Park, EBRPD

They are fairly easily identified: a small brown spider with longitudinal striping, the arrangement of their eight eyes into two rows. (The top curved row has four eyes and the bottom curved row has four eyes). They also have two prominent hind spinnerets. A spinneret is a spider's silk spinning organ. They are usually on the underside of a spider's abdomen, to the rear. On many spiders, the spinnerets cannot be seen easily without flipping the spider over; however, with Agelenopsis, the spinnerets are readily seen without having to flip the spider over. Agelenopsis spp. also have somewhat indistinct bands on their legs. One way Barronopsis can be separated from Agelenopsis is by the proportions of the posterior lateral spinnerets. In Barronopsis the proportion of the distal segment to the basal segment is 1:1, whereas in Agelenopsis it's 2:1 (distal segments twice as long as the basal). It works sometimes, but usually it's too hard to tell the exact lengths of them in photos. Especially with hairs in the way and everything. It can only be used for separating those two genera in the eastern USA, though, because some of the other (western) agelenid genera have the same proportions as Agelenopsis a lot of the time.
The spiders are easily recognized. They are brown and occur in webs. The similar Wolf Spiders do not make web. Similary to Wolf Spiders, Agelenopsis also has longitudinal striping on the cephalothorax. Eyes: 8 Eyes arranged in two curved rows of 4 eyes each. Legs: Often indistinctly banded. Spinnerets: Prominent, but better viewed ventrally. The Web: For this genus of spiders, the web is a horizontal, sheet-like web, with a small funnel-like tube off to a side (or for some species, the middle of the web) and a 3-dimensional barrier web over the top. When a flying insect hits the barrier, it falls into the sheet below. The funnel (or tube) is what the family (Agelenidae) is named for, and is used by the spider for hunting. The spider will lie in wait in the funnel, and when an insect flies hits the barrier and falls on the web, the spider will rush out, very quickly check to see if it is prey, and if it is prey, bite it. The venom is fast-acting on the prey, so once the prey is subdued (less than a second or two), the spider will drag the prey back into the funnel (for safety while eating, and to prevent other insects from recognizing the danger that lurks below on the web...) For Agelenopsis spp. spiders, the web is not sticky. If the insect lands/falls on the web, the web will actually become tangled around the prey's feet, temporarily ensnaring it in the web. Web Locations: The funnel web for Agelenopsis is a distinctive web, and often is noticed in bushes and grass, especially in the early fall mornings, where the dew has collected on the web. The webs can be expansive, covering several square feet, or just small webs in the grass.
Body Length
19 mm.
Similar Taxa
Agelenopsis can sometimes be distinguished from the similar Barronopsis by having distal segments proportional (2:1), whereas the distal segments of Barronopsis is proportioned 1:1, but the differences are more pronounced with eastern species of the Agelenidae.

Agelenopsis spp. spiders are lightning-quick; often people only get a glance of it before it disappears behind or under something.
Mainly insects.
It is common in open areas, gardens, and woodlands. Depending on the style of siding on a structure (wood shakes, some vinyl sidings, porch eaves and beams, bricks with cracked/broken mortar, etc.), it will build a web in a corner, near a light source that will attact insects. (The structure type has to be able to form some sort of gap or recess for the funnel to retreat into.)
Nesting Preferences
These spiders are very common throughout the United States and Canada. Their webs will litter low-hanging shrubs and grass in summer to early fall, and are more noticeable when dew has formed on the web.
These spiders are docile and non-aggressive. They will flee at the first sign of a threat and will not bite unless they feel threatened without an option to escape. (e.g. - Trying to pick the spider up).
Throughout the United States and Canada. Agelenopsis aperta - AZ, CA, CO, NE, NM, NV, OK, UT, TX. Agelenopsis oregonensis - AB, BC, CA, OR, WA
Active Period
Season: Often in the summer to early fall.
These spiders are docile and non-aggressive. They will flee at the first sign of a threat and will not bite unless they feel threatened without an option to escape. (e.g. - Trying to pick the spider up).
Agelenopsis funnel-web spiders only live for a year, dying in the fall (typically by the first frost). Males: Males spend most of their adult life wandering in search of a mate. Shortly after mating, the male often dies. Females: The females typically do not wander from the web, and if they do, it is typically to find a new location to build the next web. Females spend most of their time capturing and eating prey, building up their strength to mate and lay eggs. Females do not search for mates, but rather, wait for the males to wander by and find them. In the fall, after mating, the females will deposit a disc-shaped egg sac in a crevice, and then die - often still clinging to the egg sac. In some species the female camouflages the egg sac with debris.

Eddie Dunbar
Insect Sciences Museum of California

Genus Agelenopsis - Grass Spiders. ( Accessed April 8, 2017. .