Hobo Spiders
Introduction
Hobo spiders (Tegenaria Agrestis) were introduced into northwestern USA1 from Europe by commercial vessels carrying agricultural products. They were probably introduced during the early 1900 to the port of Seattle and has since then spread to states around Washington.
They are member of the funnel-web weawer spider family Agelenidae. Funnel-web spiders can move fast and the hobo spider should be capable of running up to almost 4 foot per second. It produces a flat web with a funnel like lair in the middle where the spider sits waiting for prey.
Hobo spider geographic distribution
The hobo spider can be found in Oregon, Idaho, (Wyoming2), Montana, Utah, Washington and Southern British Columbia in Canada. It will not spread to very dry areas so seeing a hobo spider south of Utah is probably not possible.
Hobo spider identification
Giant house spiders, and other spiders as well, are often misidentified as hobo spiders; there are however a number of characteristics that can help determine whether a spider is a hobo spider or not. Unfortunately some of these require a microscope and neither size or color can be used for identification.
Here are the few characteristics you can look after to exclude that its a hobo spider:
- If you can see dark rings around the spiders leg it is not a hobo spider.
- If its legs are shiny and misses fine hair it is not a hobo spider.
- If its palp are long and pointed it is not a hobo spider.
- If it has stripes on its cephalothorax it is not a hobo spider.
Note: The cephalothorax is the first part of the spiders body where to the legs are also attached.
For a more precise identification it is necessary to study its reproductive structures under a micrscope.
Hobo spiders bites
Hobo spider bites has been linked to necrotic arachnidism and systemic poisoning. In fact its true that hobo spiders can cause severe dermal damage (damage to skin) and can cause severe systemic poisoning.
In a study by Darwin K. Vest (1987)3 giant rabbits were subjected to forced hobo spider bites. The rabbits were followed to study how their lesions evolved and their organs were investigated subsequently. The study showed that male hobospiders caused both dermal lesions and organ hemorrage while female bites mainly caused dermal lesions.
Necrotic arachnidism
Poisoning by hobo spiders is called tegenarism and is hence related to the name tegenaria. It is probably the leading cause of spider envenomations in northwestern USA and Canada. The effects of hobo spiders bites are very similar to those of the brown recluse spider and often people bitten by hobo spiders think they were bitten by a brown recluse spider.
Lesser house spider or common house spider
Both named are used to describe Tegenaria Agrestis, a close relative to the hobo. In contrast to its venomous cousin, the house spider is not venomous. It is found throughout most of the US and Europe. It is very difficult to discriminate between this spider and the hobo spider as their size is approximately the same and they have the same chevron pattern on their abdomens.
Giant house spider
Until the mid-nineties this spider was known as Tegenaria Gigantea although it has later been shown that it is in fact identical to Tegenaria Duellica. It can move very fast and it is probably the fastest spider in the world as it can reach a speed of 0.527 m/s or 1,73 feet/s. Its almost as fast as the camel spider, which is not a true spider. The giant house spider is venomous although it is not known to envenomate humans. The giant spider is truly gigantic as it can reach a length of 10 cm.
Tegenaria Atrica
This spider were until recently only found in Europe and Northern Africa. Now it also found in the United States. Their legs have the same color while the legs of both the hobo spider, the giant house spider and the lesser house spider doesn't have the same color.
References
1. Exline, H. Tegenaria agrestis (Walck.), An European spider introduced into Washington State. Ann. ent. Soc. Amer (44) pp. 308-310 (1951)
2. Baird, CR. & Stoltz, RL. Range expansion of the hobo spider, Tegenaria agrestis, in the northwestern United States (Araneae, Agelenidae). J. Arachnol (30) pp. 201-204 (2002)
3. Vest, DK. Envenomation by Tegenaria agrestis (Walckenaer) spiders in rabbits. Toxicon 25(2) pp. 221-224 (1987)