By MARY PICKETT
Of The Gazette Staff
The hobo spider has arrived in Billings.

Sometimes mistaken for a brown recluse spider, the hobo, also known as an aggressive house spider, has been positively identified, says Amy Grandpre, Yellowstone County Extension horticulture assistant.

Bob Schiff, who owns a pest-control business in Billings, recently brought her a spider to be identified. When Grandpre shipped the insect to Montana State University in Bozeman, entomologist Will Lanier confirmed that it was a hobo.

Over the last couple of years, Grandpre has sent to Bozeman dozens of other spiders brought to her, but none was identified as an aggressive house spider, although several were classified as its cousin, indicating that the hobo was on its way.

The hobo spider has been in Western Montana for several years. First reported in Seattle in 1930, it became common in the Pacific Northwest in the 1960s, Lanier writes in a bulletin about the hobo.

Why the concern about the hobo arriving?

“They pack a nasty bite,” Grandpre says.

Although the spiders have not caused a death, the hobo’s bite is considerably more serious than that of many other small spiders, according to an article written by Dr. James R. Blackman in the July-August 1995 edition of the Journal of the American Board of Family Practice.

Venom from the hobo bite produces skin lesions similar to those produced by the brown recluse spider, which is not found in Montana, Lanier writes.

The initial bite of a hobo usually isn’t painful. After a bite, a small, hard area appears on the skin within 30 minutes or less and is surrounded by an expanding reddened area of 2 to 6 inches.

“Within 15 to 35 hours, the area blisters,” Lanier writes. “About 25 hours later, the blisters usually break, and the wound oozes serum. A cratered ulcer crusts over to form a scab. Tissues beneath the scab may die and slough away. In some cases, the loss of tissue may become so severe that surgical repair is needed.”

Severe headache that does not respond to aspirin is the most common symptom of a systemic illness that may accompany a bite. The headache may persist for two to seven days, and sometimes is accompanied by nausea, weakness, tiredness, temporary loss of memory and vision impairment.

People who think they may have been bitten by this type of spider should seek immediate medical attention, Lanier says.

Some doctors in Montana have mistakenly diagnosed a hobo spider bite as that from a brown recluse spider, Lanier says. Depending on a person’s age, metabolism and allergies, hobo-spider bites generally are less serious than those from a brown recluse.

People may be bitten when picking up firewood from a pile where spiders love to build webs.

“Bites also may occur when putting on an article of clothing that has been left on the floor because this is another desired spider habitat,” Lanier says.

Although not known as good climbers, hobo spiders may crawl up floor-length bedding and bite people when they are in bed. The spiders also are found in sinks, bathtubs, shoes, children’s toys, basements and closets; behind furniture; on window sills; and in garages.

The best ways to control spiders are to get rid of places spiders like to live in and to prevent spiders from entering a home.

Prime habitat, such as tall or matted grass next to a house or fence, should be cut or removed and replaced by at least 12-inch-wide gravel edging, Lanier says.

Restack lumber and firewood piles to eliminate cavities where spiders can build webs.

Seal holes for pipes and electrical lines into a house. Repair broken windows and screens and ill-fitting doors.

People working in crawl spaces or barns should wear long sleeves secured at the wrists and tuck pants into socks to prevent spiders from getting into clothing.

Commonly available insecticides are not particularly effective on the hobo spider, Lanier says.

Mary Pickett can be reached at 657-1262 or at mpickett@billingsgazette.com.