Hobo Spider Up-date
The Fact: Well, we still get an enormous response by the public to spiders at this time of the year. Most customers are concerned with the Brown Recluse Spider when they inquire about the big hairy, scary spider they just smashed. We do not have the Brown Recluse Spider in the Northwest. Until Dr. Antonelli tells us differently, I believe this. In my hometown of Chicago, they do get a few specimens collected and this is as far north as I’ve heard them being found. Most specimens that get collected that far north are believed to have been brought up from the southern part of the state. Southern Iowa is the furthest northern territory of the Brown Recluse Spider. Please spread the word about this.
Identification: In our area, we have a complex of three species of house spiders. Unfortunately, all three species look very similar. The three species include the domestic house spider, Tegenaria domestica, the giant house spider, T. gigantea, and the Hobo spider, T. agrestis. Visual characters that we previously used to ID house spiders are inconsistent and have lead me to misidentifications when these are all I use. Thanks to the UW Burke Museum, we have reliable characters. In the Master Gardener office, there is a description of the male pedipalps (two bulbous appendages by the mouth parts) that is reliable in separating the different species. I have left directions on how to look at the pedipalps. You will need to use the microscope to do this but I HIGHLY recommend you do to learn the features, since these spiders are considered very important by the public. Once you get the hang of it, it is very easy and I will be very happy to help you learn this. These characters will only work for males but 99% of the house spiders brought in this time of year are males.
The Status: Now that I have a better handle on identifying house spiders, I have a better sense of what comes into our office. Of all spider specimens brought in, less than 2% have been hobo spiders. Almost all house spiders collected are gigantic house spiders (the good guys). Do you remember Dr. Antonelli’s prediction? Well, I think he’s right. In Europe, where all three species of house spiders came from, the hobo is not a problem inside the house. The hobo spider was introduced prior to the giant house spider. Now the giant spider population is increasing, while the hobo spider is decreasing in frequency of occurrence. The giant spider is a fierce competitor (and sometimes a predator) of the hobo spider and will keep hobo spiders out of its territory. In addition, the giant spider is relatively harmless and bites are rare. This is why hobo spiders are not much of a problem in Europe; they are naturally controlled.
The Problem: Many of our customers (and ourselves) hate spiders. Every fall, people are reminded of how much they despise spiders because they are paying unannounced visits to our houses. Keep this in consideration when you discuss spider ‘problems’ with customers. During late summer to early winter, males are on the search for females, so they will be running everywhere in hopes of an encounter. When males enter a house, it is usually through ground level or below ground level openings. As far as I know, both hobo and giant house spiders do this during the fall season. As long as we are in the PNW, we will hear about spiders every fall.
The Real Problem: All spiders are venomous. Even though I am confident that the occurrences of hobo spiders are on the decrease in households, spiders should be handled with caution regardless of the species. Even after identification, it is still good to suggest caution to the customer next time they encounter a spider. Bites are relatively rare considering the number of hobo spiders in our area. Severe bites resulting in necrosis usually occur when the spider is trapped up against your skin. If you roll over onto one in your bed, that poor spider has all night to bite you (hobo bites reportedly produce little or no pain).
Preventing: For in-house encounters, identify the route the spiders are using to get inside. Sticky traps work very well in helping you identify these areas. Places to look include cracks in the foundation, gaps in windows and gaps under doorways. In fact, there is a commercial trap available now for the hobo spider (http://www.hobospider.com/). The trap claims to have an attractant and does catch spiders. I’d be interested to hear from anyone that has used this trap. Once the route is determined, simply barricade the area that the spiders are using to get in. At my house, it was the gap underneath my front door. I simply used window adhesive to close the gap. For large infestations underneath the house or in basements, chemical control may be a consideration; however, this will not prevent future problems. When moving any debris or wood out side, wear protective clothing and gloves. This is also very important when venturing into areas of known infestations such as a crawlspace. Be sure to check your gloves and shoes before you put them on, this is the most common scenario for a bite. If you are worried about the nighttime visit, be sure that your bed is not touching the wall and no blankets are touching the floor. Additionally, consider buying a bed frame. Many students in Pullman (and I bet at Western also) get bitten because they just have a mattress on the floor. Oh yes, and keep your mouth shut when you sleep…
For tons of great information on hobo’s see http://hobospider.org/
For hobo spiders in Whatcom County see http://whatcom.wsu.edu/ag/homehort/pest/hobo.html
For an excellent page to identify Hobo Spiders: http://pep.wsu.edu/pdf/PLS116_1.pdf
For additional Whatcom County spider information: http://whatcom.wsu.edu/ag/homehort/pest/spider.htm
To reach Todd Murray please call (360) 676-6736 or e-mail him at: firstname.lastname@example.org