On a mission

On the wall beside my desk, a male running crab spider made a thorough search, running up, down, across and back, looking behind shelves and furniture. He didn't find what he was looking for; I could have told him that and saved him the trouble. He was the only spider on that wall. The nearest female was outside, by the back door.

Philodromus dispar, adult male. About 5 mm. long, eyes to spinnerets.

The female he was hunting for is slightly larger than he is, and dressed in mottled light brown. Only the mature males wear black decorated with those whitish stripes down the sides.

They are hunting spiders, always on the move, chasing down their prey rather than sitting in a web waiting for it. But when breeding time comes around, the male forgets to eat and wears himself thin racing, racing, racing; looking everywhere for a mate. Does he know what he wants? Probably not; he just feels the need to run and look and look again. But he'll know her when he finds her.

On his way up again, just in case he missed her. The "boxing glove" ends of his pedipalps are another sign of a mature male.

He's examined that wall and the curtain at the window, and has moved on. Only a few metres left to go before he discovers the female's hangout. I wish him luck.

The lure of plastic

A male Philodromus dispar spider moved into my spider house while it sat outside with the lid open, airing out. I closed it up and brought it in, but after a couple of days, the spider was unhappy with the arrangement. He kept running and running and running, never stopping, for hours. Looking for a mate, I guessed, and opened the top for him. He scampered up and out; I let him go.

On my desk, there's a plastic bottle of aerated water that I use to spray critters that need to be kept damp. When next I saw "Philo", he was climbing up the bottle. When he got to the top, he stopped abruptly, put his pedipalps down against the plastic, his rear in the air, not a customary pose for these active spiders. And then he just stayed put there, as though his pedipalps had been glued down. I shooed him along, and he moved an inch or two and repeated the pose, pedipalps to the plastic.

"Interesting stuff! Smells like ..."

He's a mature male, shown by the large "boxing glove" ends on his pedipalps*; he uses these to transport sperm to the female's genital pore. But why does he want to make contact with this particular plastic? Is there some chemical in the plastic that reminds him of a female's pheromones?

Now that I think of it, was it the smell of the plastic, just outside his house, that drove him frantic in the first place?

Questions, questions. I haven't found an answer.

After a bit, since he wouldn't leave the top of the bottle on his own, I shook him off by the outside door. In the morning, I found him on a vinyl chair in the kitchen.

*Alex Webb has an astounding photo of a male black widow's pedipalps; go take a look!

Huntress

Looking for slugs in my garden, I found this big spider, instead:

She's probably a Philodromus, a running crab spider of some sort. It's hard to be sure, because a defining characteristic is that the second pair of legs is longer than the first. And all she's got in second place is a broken stub.

One advantage of having eight, I guess; she's doing fine with two gone.

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Good-looking, well-dressed single male

... with hair on his pedipalps, looking for a date ...

Philodromus dispar, male

... or a good meal, whichever comes first. He can have all of my mosquitoes. In fact, I hope he does.

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