The hobo spider (Eratigena agrestis) is a common arachnid often found in the Pacific Northwest region of the United States. While its appearance and funnel-weaving habits can cause concern, this spider is primarily a quiet predator of small insects. Its diet consists mainly of various arthropods, and its feeding behaviors are highly specialized and influenced by its immediate environment.
Primary Prey and Consumption Habits
Hobo spiders are generalist predators, meaning their diet includes a variety of available small arthropods. Their main prey consists of ground-dwelling and low-flying insects such as ants, flies, and beetles. They will also opportunistically consume other small spiders when food sources become scarce.
After immobilizing its prey with a quick injection of venom, the hobo spider does not chew or swallow solid food. Like many other spider species, it uses a process of external digestion to consume its meal. The spider regurgitates enzyme-rich digestive fluids onto and into the captured insect, which effectively breaks down the prey’s internal tissues and organs.
This process turns the insect’s interior into a liquefied substance. The spider then uses its sucking stomach and tube-like mouth to draw up the nutrient-rich liquid, leaving the hard exoskeleton behind. This method of consumption allows the spider to efficiently absorb the nutrients from prey much larger than its own mouthparts.
The Funnel Web Hunting Strategy
The hobo spider is classified as a funnel-web spider due to the distinct shape of its silk trap, which is not to be confused with the webs of the dangerously venomous Australian funnel-web spider. The web is constructed as a flat, horizontal sheet of non-sticky silk that stretches across a surface, often near the ground. At one end of this sheet is a narrow, tubular retreat, which gives the web its funnel shape.
The spider remains hidden inside the funnel’s neck, which provides shelter and an ambush point. The non-adhesive sheet web acts as a trip-line system, where the spider relies on its sensitive legs to detect vibrations rather than sticky threads. When an unsuspecting insect crawls onto the sheet, its movements cause vibrations that alert the spider to the meal’s presence.
The hobo spider then exhibits a burst of speed, darting out of the funnel retreat to rapidly attack the entangled prey. It quickly injects venom to immobilize the victim and may use silk to further secure the struggling prey. The spider, a swift runner, then drags the captured meal back into the safety of the funnel retreat to begin the process of external digestion.
Environmental Factors Affecting Meal Selection
The hobo spider’s diet is largely determined by where it builds its web, as prey availability is the greatest influence on meal selection. Outdoors, where the spider is most commonly found, webs are built in locations like tall grass, under rocks, or near woodpiles. This outdoor environment offers a diverse menu of field-dwelling insects, including various grasshoppers and flying insects that land near the ground.
When these spiders venture indoors, typically in search of mates or shelter, they are restricted to what is available at floor level, since they are not adept at climbing smooth vertical surfaces. Webs built in basements, crawlspaces, or garages will therefore capture common household pests. This indoor diet may include insects like houseflies, cockroaches, or earwigs that move along baseboards and into the low-lying funnel webs.