Spiders shouldn't cause panic

By Marianne C. Ophardt, Special to the Tri-City HeraldSeptember 21, 2012 

PASCO, Wash. -- Last week, I heard from a friend about one of her coworkers who ran from her office screaming.

She was in such a panic that it took several minutes to determine that a spider was the cause of her distress. A bit extreme, but I can empathize with this person.

I used to be afraid of spiders, but over time I've learned to appreciate these eight-legged beasts. I can't say I want to keep them as pets, but you won't find me screaming if one shows up in my office.

Late summer and early fall is when area residents seem to find the most spiders inside their homes. This is erroneously attributed to the cooling weather and the need for spiders to find a warm spot for the winter. Rod Crawford, Curator of Arachnids at the University of Washington's Burke Museum, points out that this is a myth.

Many spiders found inside of the home are "house spiders" that spend their lives indoors and are adapted to the dry environment, moderate temperatures and limited food supply found in homes. House spider species aren't adapted to outdoor conditions and probably would not survive if you kindly scoop them up and deposit them outside. Outdoor spiders that find themselves inside a home aren't likely to survive long either.

Crawford points out that only 8 of the 170 species of spiders found in Seattle are commonly found outdoors and in houses. Yet, some outdoor spiders do find their way indoors at this time of year. One of these is the hobo spider (Tegenaria agrestis) that wanders about in late summer and early fall looking for a female mate. Since female hobos are seldom found indoors, the males have definitely gone astray. You have to feel a little sorry for these star-crossed guys. They can't find their love, and they won't survive indoors.

Talk about bad luck. For years, the hobo spider (initially called the aggressive house spider) has been blamed for being aggressive and poisonous. Hobos were misnamed "aggressive" because of their species name agrestis, which in Latin means "rural."

Also, hobos may not be poisonous. Arachnid specialists such as Crawford are casting doubt on past assumptions that the hobo spider bites are poisonous and cause necrotic wounds. Crawford points out that during the past 25 years, not one patient has come forward who was initially healthy, developed the "typical hobo spider bite symptoms," and was able to produce any spider that had bitten him/her.

Crawford also notes that, "within the range of the brown recluse, genuine necrotic-bite patients recover the spider about 20 percent of the time, so hobo spider victims should have managed it at least once.

"On the other hand, several humans and dogs developed no significant symptoms when bitten by hobo spiders that were recovered and identified. Some such cases can be explained as 'dry bites,' but it seems increasingly likely that these cases, or most of them, are not actually being caused by a spider."

Finally, Crawford points out that it has been illogical and unfair to blame all the necrotic lesions that occur in this region on the hobo spider. There are many possible causes of a necrotic skin lesion, and anyone who discovers one should consult medical experts.

* Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

Tri-City Herald is pleased to provide this opportunity to share information, experiences and observations about what's in the news. Some of the comments may be reprinted elsewhere in the site or in the newspaper. We encourage lively, open debate on the issues of the day, and ask that you refrain from profanity, hate speech, personal comments and remarks that are off point. Thank you for taking the time to offer your thoughts.

Commenting FAQs | Terms of Service