Hobo Spiders 101

Scientific Name: Tegenaria agrestis

Why call them hobos? Because they hitched a ride some time ago and settled in America. Hobo spiders are native in Europe. They didn’t come to America through Ellis Island or the Port of New York. They landed in Seattle.

Maybe hobo spiders came to Seattle as eggs; maybe just one sac of eggs attached to one pallet. More likely, thousands of egg sacs on hundreds of pallets. Or maybe, a nest of the spiders. In any event they have spread from the Port of Seattle through almost all of Washington, Oregon, Idaho, and into Utah. These partially documented aliens can’t be deported and they appear to have social security.

Where Hobo Spiders Live

In Europe hobo spiders are found in the fields, seldom in houses. In America they have become urban dwellers, an interesting adaptation. However, the American experience is not fully indoors. Here hobo spiders commonly are found in gardens and yards, as well as near house foundations and basements.

What do Hobo Spiders Look Like?

Hobo spiders are large. The body, thorax and abdomen, may be one half inch or more. The long legs extend so that the spider would encompass a silver dollar. The legs have a light color and the body is a little darker.

How Big are Hobo Spiders?

The average size of a mature Hobo Spider is approximately 1/2 to 3/4 of an inch, with a leg span of 1.5 inches.

Hobo Spider Webs

Classified as funnel web weavers, hobo spiders weave a layered web which has a funnel-like lair at the rear where the spider waits for its prey. The web is not sticky, but is a “trip web” which traps the insect prey that is unable cope with the surface. The funnel web weavers, including the hobo spider are noted for rapid movement. When the web shakes, they get to the prey quickly.

Hobo Spider Bites and Effects

Why Hobo Spiders Bite

The eyesight of hobo spiders may not be keen. The spider won’t be able to distinguish among humans well enough to know they may not need to be on the defensive. In other words, the hobo spider will assume he is being attacked and he will fight back with the only weapon he has, venom. About half of the bites of hobo spiders on humans will be “dry” bites which are harmless.

The Effects of a Hobo Spider Bite

The venom of hobo spiders will have local effects, a large area of redness around the site of the bite. This usually disappears a few hours after the bite, much like a mosquito bite. However, within 24 to 48 hours from the bite, there may develop some blistering at the bite site. In another 24 hours such a blister may burst to give an open ulceration. Within a few days a scab will appear over the lesion. After about three weeks the scab will slough off and the lesion generally heals, leaving a scar. When the bite is delivered to fatty tissue, the local lesion may be deep and extensive and may not completely heal for two or three years.

People bitten by a hobo spider often have reason for concern. In the past few years hobo spider bites have become the number one spider-inflicted medical problem in America. This, even though their range is only in the Northwest part of the country. For this reason, care should be taken by people working in such places as a dark basement or the crawl space under a dwelling. Be especially cautious during the late Summer.

Protecting Yourself Against Bites

Good practice includes full body coverage whenever entering the hobo spider might consider their own domain. Tuck the pants into the stockings. Wear gloves with long sleeves tucked into the gloves. Leave few, if any, crevices where a spider can invade the area between the body and the clothing. A trapped hobo spider might inflict numerous bites as it tries desperately to escape from a threatening entrapment.

The Hobo Spider Life Cycle

The Hobo spider life cycle may be one year; it may be two; this is subject to argument among the experts.

When a Hobo spider reaches its full adult size in June the males and females spend the Summer preparing for egg laying and fertilization in the Fall. The eggs from a female will be deposited in one to four egg cases in late September or October. These egg cases are layers of silk intermingled with layers of soil and debris. They are usually attached to the undersides of rocks or other items found in yards or gardens. Each case may contain 100 or more eggs. Usually, they are not in human living quarters, although they may be in the crawl space under a house. By the time the eggs are secured, there are very few males around, indicating that they die soon after fertilizing the eggs. Who knows, they may be eaten by the females, like the black widow spiders, but this has never been observed.

The eggs hatch early the following June. Since colonies studied in the summer include full grown adults mixed with juveniles, it has been assumed that there is a two year life cycle. During the last half of a summer season many of the mature males will be exploring everywhere they can to mate. This is when most of the encounters with humans take place. At such times there may be large numbers of male hobo spiders entering houses, crawl spaces and basements. There they are seen and come close to people, who are surprised by such large spiders in large numbers.

The male hobo spider will present two protuberances that vaguely resemble boxing gloves. These are not fangs or poison sacs, they are the male genitalia. The female will not have these protuberances, they will have large abdomens where the eggs are being developed. The females seldom wander into human houses.