Sunday, May 20, 2012

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!


  1. Could the plastic have picked up pheromones from the creatures you mist?

  2. Wow. Super interesting. Nicely observed. =)

  3. Upupaepops; Good question! I don't really think so, because I always spray them from a distance, so as just to mist them and not dislodge them from their place. But yes, all possibilities must be considered.

    Thanks, biobabbler!


If your comment is on a post older than a week, it will be held for moderation. Sorry about that, but spammers seem to love old posts!

Also, I have word verification on, because I found out that not only do I get spam without it, but it gets passed on to anyone commenting in that thread. Not cool!