365 Urban Species. #098: Woodlouse Spider

[urbpan]

Urban species #098: Woodlouse spider Dysdera crocata

While handling this spider trying (unsuccessfully) to get a better photograph, I became unnerved when I noticed its fangs. Usually on a spider this size (maybe 3/4 or an inch, or a little less than 2 cm) the fangs are inconspicuous, tucked away underneath. The woodlouse spider has long, obvious fangs, presumably strong and sharp for piercing the shell of their crustacean prey. Most spiders' fangs are not strong enough to bite through human skin, but some are, and this individual looked capable. But it showed no inclination to bite, instead clambering in a panic to remove itself from the light.

Research after the fact indicates that it indeed could have bitten me, but it wouldn't have injured me seriously. Or to use some delicious technical language: "D. crocata bites have been implicated in causing a localized, intensely pruritic rash with coalescing dermal papules 4-5 mm in diameter.  The bites apparently do not result in any systemic neurotoxicity or cytotoxicity." (http://www.ento.psu.edu/extension/factsheets/Spider/spiders.htm)

The woodlouse spider, unsurprisingly, is found anywhere woodlice are. Under logs and stones and other debris near buildings is where you will most likely encounter one. They were apparently introduced to North America and Australia, along with their favored prey, from Europe. It's possible that no introduced woodlice are considered invasive because their predator comes along with them when they travel.

Comments

Re: Just found one where I live on Cape Cod

[urbpan.livejournal.com]

Take it easy. You killed a big female who came in from the cold. There may be more around, but spiders don't swarm. As predators, they can only grow to numbers that can be supported by the amount of prey around. You'd need plague numbers of isopods to have even modestly large numbers of woodlouse spider. Also, big as their fangs are, they don't have venom that harms us. An animal like a horse wouldn't even notice them, and a spider has no reason to bite a horse. The only reason humans get bit by spiders is that they get inbetween our clothes and skin.