The Larimer County Extension Office has recently received phone calls from homeowners in Fort Collins and Windsor about the threat of the hobo spider. Calls stemmed from a pest control company going door-to-door selling products to eradicate spiders. During the sales pitch, the company makes claims that a neighbor has either been bitten by a hobo spider or has complained about hobo spiders near his or her home.

The company then presses the claim that the hobo is a dangerous, venomous spider and the foundation of the home must be sprayed with an insecticide to reduce risk of injury to pets and children.

The Denver Museum of Nature and Science has conducted a Spider Survey for many years, mapping locations of identified spiders. According to DMNS records, only one hobo spider was trapped in Loveland, the northern most point the spider has been reported. Many hobos have been identified in the Denver and Boulder areas, so the spider may be adapting to northern climates.

The hobo spider (Tegenaria agrestis) is an introduced species from Europe. It is a field spider, taking residence in agricultural areas, acting mostly as biological control. The nickname "hobo" was given to the spider because of its spread using railways, and though another name for the arthropod is the aggressive house spider, it is not aggressive. The hobo was introduced on both the east and west coast of the United States.

The hobo spider is a funnel weaver, brown in color and 1/4 - 5/8" long. It looks very similar to the domestic house spider (T.domestica), and without a microscope, the two are impossible to distinguish. Funnel-weaving spiders have horizontal webs, often spun across bricks, vegetation, wood or stones. The webs catch dew in the morning, making them more noticeable.

The claims that the hobo spider causes necrotic wounds similar to the brown recluse have not been proven. Numerous research studies have been done on hobo spider venom and there is no evidence the venom is poisonous. In fact, the spider is not considered dangerous in Europe. Those bitten by the hobo spider may suffer from allergic reactions, which could be caused by bacteria on the spider's fangs ("pinchers").

Here are some handy tips for consumers:

Before deciding to pay for any service, it's a good idea to check the company's references. The company should not hesitate to give you this information.

If the company says that multiple neighbors are complaining, or they give a specific name of a neighbor, ask which house. Talk to the neighbor.

Contact the Better Business Bureau (mountainstates.bbb.org/). Check if the company has valid credentials or if they have had complaints.

Call your local Extension Office. Extension Offices offer valid, research-based information.

With fall approaching, you may see more spiders in or near the home. Like many creatures, they gravitate towards warmth and water. While many people dislike spiders, remember they are beneficial, keeping other insect populations under control. The one spider that all Coloradoans should be aware of is the black widow spider, which is dangerous and can be harmful to humans. This spider prefers dark corners and wood piles. It is shiny black with a red hourglass-shaped figure on the bottom of its abdomen.

For more information, see Colorado State University Fact Sheet #5.512, "Spiders in the Home."

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Colorado State University Extension provides unbiased, research-based information about family and consumer issues, horticulture, natural resources, agriculture and 4-H youth development. As part of a nation-wide system, Extension brings the research and resources of the University to the community. For more information visit www.ext.colostate.edu or www.AnswerLink.info where answers to everyday questions are available 24 hours a day, seven days a week.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  August 17, 2007