Some Clarification on 'Hobos known for bad attitude'

by Antonio Ariza Morena


This article was written by ANTONIO ARIZA MORENO <l95aa@tay.ac.uk> to offer some clarification to the 'Media News' item in Vol1. No 9. of Arachnids Weekly

The explanation for the lack of 'accidents' with Tegenaria agrestis (which is an extremely widespread species all over Europe) is the fact that it is a strictly rural species in Europe, as indicated by its name. This species is never found near human lodgings, gardens, towns. etc... and can only be encountered in rural places where there is little human presence or in wild habitats where there is no human presence whatsoever. Supposedly the reason behind this lies in its cousin Tegenaria gigantea, which is found all over Europe, inhabiting rural and metropolitan areas with a high incidence of human presence.

T. gigantea is an enormous spider for European standards, being one of the most aggressive species I know (which is no wonder when we take into account its life style) and, when confronted by the much smaller T. agrestis, will usually win and make a good meal out of its cousin. T. agrestis can't compete and its presence is therefore relegated to fairly inhabited parts of the countryside.

Even though T. agrestis bites are almost unknown in Europe, T. gigantea bites are fairly common, which is due to the fact that these spiders are probably the most common species in inhabited areas and that they are found living in our houses all the time. This species is able to go a very long time without water, a very important factor since the inside of a human home is among the driest places that can be encountered, and without eating as well. The last point may be crucial in explaining their aggressive behaviour since they will not doubt and attack anything that moves, even when it is several times larger than they are (and, as I said before, these spiders are already fairly large) and this is essential if they want to survive in the hostile environment they have chosen to live in. When food is scarce, one has to try to subdue and eat everything that comes across one's path ... or, in this case, funnel web.

It is a common sight to see males of this species running over the carpet and anything else in European houses from late August until the first frosts and in flats like mine (on the groundfloor with a garden in the backyard) it is normal to wake up in the morning and find one or more of them trapped in the bath or sink.

Their bite is very painful, which is no wonder when you look at their huge chelicerae (quite impressive for an araneomorph spider), but no symptoms of extreme swelling and necrosis of the affected tissue (normal symptoms of T. agrestis bites and which are scientifically known as 'Tegenarism') can be observed, even though the bite may hurt for a few days.

When T. agrestis was exported to the American continent, it found that it had no competitors and could easily usurpate and conquer the habitat it had been denied in Europe. Life may not be much easier in human dwellings, but it is much more comfortable, warmer and there are definitely less predators than in the wild. It seems that T. agrestis has been establishing itself and spreading over the North American continent for a much longer period of time than T. gigantea, and even though the latter of the two species may still win and get rid of the T. agrestis menace, this may still take a long time or not happen at all. The other factor that has allowed its spread over the North West of the USA and Canada is the fact that this species is very well adapted to cold environments, much more than other Tegenaria species and obviously more than other Native species that could have represented a threat to it, like the different recluse and widow spiders. Hence, since competition is almost non-existent, there is little that can be done to stop it from spreading further and further south.

By the way, I've always kept some T. gigantea (or at least I think they are T. gigantea, there is much confusion about this genus and many of its species are extremely similar) and still have two huge females. Each of them has produced over six fertile eggsacks this year and I'm using the spiderlings to feed my Cyclosternum fasciata spiderling, one of the smallest tarantula spiderlings that I've ever seen.


 
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