There’s a spider in the house

Some kinds of bugs are notorious for finding their way indoors during the coldest months.

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Photo by Matt Pelikan

For someone who enjoys the study of insects and spiders, deep cold and deeper snow represent mighty hard times. I’m pretty much reduced to hoping for a thaw.

But there are a few arthropods that turn up quite regularly in winter — inside houses. Some kinds of stinkbugs, leaf bugs, and ladybugs, which naturally seek sheltered enclosures in which to overwinter, are notorious for finding their way indoors and popping out during the coldest months. Cellar spiders, as their name suggests, often prefer a basement to any natural environment, and these gangly critters can be found inside in various numbers year-round.

But during much of the winter, the bug hunting inside is no better than it is outdoors. So I was pleased when a spider recently tumbled out of a ceiling fixture in which I was changing a light bulb. Long-legged, pale brown, subtly speckled, and with a body about the size of a dried kidney bean, it lowered itself just in front of my face on a strand of silk.

It’s very possible I feel differently about spiders than you do. I can’t say I totally lack the visceral fear most people seem to feel about spiders; handling anything other than a small one makes me mildly uneasy. But my main reaction to a spider is curiosity: These are remarkable animals, coming in an astonishingly wide range of forms and exhibiting life histories that vary just as dramatically. And they play a vital ecological role in regulating the populations of a huge range of prey species. So my interest was piqued.

Caught by surprise on a stepladder, with a screwdriver in one hand, I was not in a position to snag this spider when it bailed out in front of me. And when it hit the floor, it put on a remarkable burst of speed, dashing sideways to concealment under the baseboard radiator.

Over the next week or so, I saw the spider several times, sometimes clinging upside-down to the ceiling, sometimes in a corner of the ceiling and a wall, where it wove sparse, seemingly random nets of invisibly fine silk. These looked to be intended simply as a comfortable place to hang out; they were too small and disorderly to have any hope of catching an insect. Whenever I tried to get a close look at my new friend, it rappelled to the floor and disappeared.

Finally I caught it unawares as it idled on a wall. I stealthily went for my camera, turned on all the lights in the bathroom, and took a few shots. Then, very slowly, I moved my hand close to the spider, and when I gave it the gentlest of nudges, it transferred to my hand. I one-handed a few more photos, then brought the spider down to the baseboard radiator and, with a puff of breath, blew it under. That was the last I saw of it, but I bet it’s still around.

The pictures, taken in dim, artificial light, were poor, but I got to work on my favorite arthropod ID web site, BugGuide.net. Scanning representative photos of spider families, I explored groups that had members resembling my little buddy. One pronounced characteristic turned out to be especially useful: The longest legs were the second ones from the front, an unusual thing in spiders, and strong evidence that mine belonged to the family Philodromidae, or so-called “running crab spiders.”

A fairly diverse family of about 30 genera and 500 species worldwide, running crab spiders typically show the speed and habits I had observed. They run their prey down by bursting from ambush like tiny eight-legged cheetahs, reserving their silk for other applications like egg sacks, simple structures like the corner perches I observed, and lines for descending.

One very large genus of this family is named Philodromus, and it didn’t take to long to determine that my spider was a member of this group. Its relatively plump body meant that it was a she. And it turns out that Philodromus, as a genus, tends to be more or less adapted to cold. Some species have found to be capable of not just moving, but capturing prey, at temperatures slightly below freezing. But tolerating cold doesn’t mean you like it, and unsurprisingly, Philodromus is another of those bugs that tends to invite itself indoors during the winter.

So there you have it. A classic Philodromus sighting! Unfortunately, the species in this genus are all very similar, and while I can narrow the identity of mine down to a half-dozen or so, I doubt I’ll ever be able to give her a species name. But I was grateful for her visit.