Grass spiders are common arachnids found throughout North America. They are well-known for constructing distinctive funnel-shaped webs, which can become quite conspicuous in lawns and gardens, especially when covered in morning dew. Despite their appearance, grass spiders are generally shy and not considered aggressive towards humans.
Appearance and Identification
Grass spiders have specific physical characteristics that aid in identification. Their body length typically ranges from 1/4 to 3/4 inch, with females generally larger than males. The body is often light brown, gray, or tan, featuring two dark brownish bands that run lengthwise across their cephalothorax, the fused head and thorax section. Their abdomen is usually oblong and brown, sometimes displaying a reddish-brown zigzag stripe or a series of chevrons.
These spiders have eight long, slender legs covered in fine hairs, often banded or striped with darker and lighter segments. A distinguishing feature is the pair of prominent spinnerets at the rear of their abdomen, which are long and extend beyond the body. While they possess eight small eyes arranged in two horizontal rows, their primary sense for detecting prey and threats relies more on vibrations.
Habitat and Web Structure
Grass spiders typically build their webs close to the ground in outdoor settings. They are commonly found in lawns, tall grasses, meadows, gardens, low shrubs, along fences, and near building foundations. Their webs are sheet-like and non-sticky, often laid horizontally across vegetation, with a funnel-shaped retreat at one end. This funnel can lead to a sheltered spot, such as dense foliage, a crevice, or under a rock.
The sheet portion of the web can extend up to three feet wide, with the funnel retreat sometimes measuring over a foot long. This intricate structure serves as both a hiding place and an ambush point for the spider. Flying insects may collide with barrier webbing above the sheet and fall onto it, or crawling insects may wander onto the mesh-like strands. The funnel web’s design allows the spider to quickly dart out from its concealed position to capture prey.
Behavior and Safety
Grass spiders are timid. When disturbed, they typically retreat quickly into the safety of their funnel-shaped web. Their hunting strategy involves waiting patiently within the funnel for vibrations on the web to signal the presence of prey. Once an insect lands on the non-sticky sheet, the grass spider swiftly rushes out, delivers a venomous bite to subdue it, and then drags the prey back into its funnel to consume.
Bites from grass spiders are rare and generally occur only if the spider feels threatened or cornered. Their fangs are small and may have difficulty penetrating human skin. Should a bite occur, the effects are usually mild and medically insignificant, often described as comparable to a bee sting. Symptoms typically include localized redness, slight swelling, or itchiness at the bite site, which resolve quickly. Grass spiders are harmless to humans and play a beneficial role in controlling insect populations.