First - a photo of exactly what these spiders look like in their usual location. This is Gutsy, so named because she stays way out on her web no matter how close I get. Most black house are pretty shy and retreat as soon as they detect my presence. Gutsy has her web funnelled into a crevice in the brick work on the edge of the window frame on the right of the photo. Hence there is no way of seeing into her retreat.
But there is often a Little Guy as well. I have noted these before, photographed close up enough to see the engorged palps which indicate a male. They seem to arrive about the time that the females become mature. I have even watched one of the Little Guys mate - or so it seemed - with a recently moulted female. Males of quite a few spider species will hang around a females web and mate with her just after her final moult. She is finally able to mate but still fairly defenseless with her body soft from the moult. In Pane 12 today, there were all three - Little Guy is out to the left:
"I have recently surprised myself and become extremely attached to what I discover from your posts, is a black house spider. She lives in the window of our shower and so every morning while I'm showering I catch up with her and observe her incredible life. I read in some posts of yours about this spider, that you had observed some very small individual spiders sharing the web. Did you ever find out what these were? I have been assuming that they were the male. I have a few other females living in various parts of the house and they all seem to have a small spider in with them at the moment."
I have spoken to arachnologists who were unable to tell me what was going on. They are still pretty busy just classifying our spiders - most have yet to be done. The only way they could investigate was if I killed a little guy to go under their microscope. I couldn't do that! I am irrationally obsessed by my spiders. So what is going on?
I have two theories:
1. Maybe these little guys are kleptoparasites, much like the small dewdrop spiders Argyrodes species (Family Theridiidae), who hang around on the webs of larger spiders, such as the golden orb weaver (Nephila sp.) webs, and pinch their host's prey. My Little Guys are the wrong shape for a theridiid, but maybe they are another species of kleptoparasite.
2. Are these the males of the smaller species, the grey house spiders (Badumna longinqua)? Maybe the two species, being the same genus, can't tell the opposite gender of the other species from their own. That is not unknown in spiders, but only the same species has genitalia which matches perfectly, and hence they can mate successfully.
I don't think they are kleptoparasites because they seem to only arrive when the females reach maturity. But they are also smaller than I would expect for the males of B. longinqua. So it is a mystery.
I am really hoping that wolfatron will watch his Badumna and we can exchange notes. I also hope to hear from any other Australians who have these fascinating creatures and can watch them as well. Or maybe you have a different theory. I'd love to hear from you in comments or by email.
Oh, and an update on Guy-in-one and Girl-in-one. She killed him. Having told you how they can happily cohabit, I couldn't see him through the glass yesterday. I went straight outside and looked up. There was his body, strung up in the web - dead. I like to think that he died of natural causes, but I have to face the truth. She just didn't want him around any more. Now to watch Guy-in-12 and hope that he leaves of his own accord.