Friday, December 17, 2010

The Mystery of Black House Sex

OK, this post won't win any awards for photography, but I have been puzzling over the antics going on in the webs of mature female black house spiders (Badumna insignis), introduced in the December 10 post. There are almost no behavioural studies done on this spider, despite how common they are. The mystery is all about sex and size. Spider sex and spider size.

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.

Some black house spiders make their webs on the panes of glass on the back door. I can see into their retreats - not perfectly - they cover the glass with silk. This is a pair in Pane 12. Guy-in-12 and Girl-in-12 have been together for about 2 weeks now. They are often touching, so definitely a pair. I photographed them with a ruler, so you can get an idea of their relative size. Guy-in-12 is the smaller of the couple.

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:

So who are these Little Guys? They are in most of the webs of my mature females. I had mentioned this on another site, and received a fascinating comment on the December 10 post. wolfatron wrote:

"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.


  1. Hi Lynne, I mistakenly added a post onto my original post with some updates about my girl. Check it out. In short, she's had some babies. Unfortunately, we were away for about 3 weeks prior to them hatching so I don't know if there was a larger male in the web. Certainly the first visitor I saw was nowhere near the size of the big male in your photo above. Alot like the little guy.
    I was wondering, how long should I expect the babies to be in the web for? And, do you know whether or not when they leave, do they tend to make their own webs close by?
    We have lots of orb weavers as well this year. In fact, we are relocating some of them as they are making their webs where we walk at night.
    I have some photos that you might like to see, but I could only upload my profile photo.
    BTW: This "wolfatron" is a "she":)

  2. One other thing, have you got any idea what the spiderlings eat? I have not ever seen any tiny bugs or anything in the web and as you've pointed out information about these spiders is scarce. I wonder if Mum is feeding them? They do seem to have times when they are all much closer to her. Sometimes she seems to cover them completely with her body.

  3. Hi wolfatron,

    Now I get to answer here as well. I still see the little guys in every web, but also the larger males. And the even larger females. But you can now see that the little guys are much bigger than the babies, and they leave long before they get to that stage.

    I can't wait to see the photos. Wouldn't it let you upload them? I'll get Damian to check the settings. Otherwise, I'll get you to send them to me to upload.

    I find the babies tend to leave when there is a warm breezy day. But some still hang around. They don't seem to come out as a single hatching like the daddy long-legs. But then again, there are a lot more of them per egg sac.

    They balloon off on little silk threads. If you are lucky, you get to see it. Hard for them to do inside! I have seen some land nearby, and move into the edges of other webs, or start their own. But most head off into the big world.

    The reason that you don't see them eat is that they don't. They are still living on the remains of the egg sac provisions. They will not develop proper feeding parts until they moult again. It is a good idea to have dispersed because otherwise they partake of sibling-dinner. I have never seen them stay in the web and grow. They have always left. I did see one very strange sight with Gutsy's babies, but that will have to wait until I have time for another blog. Life suddenly went into overload, as it has a tendency to do. I have also seen what looks like protective behaviour of the blackhouse mothers. All this is original observations. There is almost nothing out there about their behaviour in the wild.

    Although the general story is that they disperse before they start feeding, it isn't always true. I have seen the little common house spiders (Achaearanea sp.) (aka American house spider) go through their first moult still around their mothers, and then group hunt. I have photos of that somewhere. I should do a blog on them because you will certainly have them at home. They are the most widespread spider in the world. They look like little pale readbacks, because they are the same family - Theridiidae. Totally harmless and great to watch once you have detected them.

    I'd love to exchange observations on them, too.

    So good to hear from you again!

  4. Oh, and Guy-in-12 did leave of his own accord and move in with another female. I miss them!

  5. Yep, the little guys I see stay for a couple of days and then move out. They are bigger than the babies and of a finer build. There seems to be a group of my babies that have settled on NOT moving out of home early!! Mum doesn't seem to mind and indeed was out a long way of the web last night, very relaxed.
    I took a photo last night of another one of my black houses who had two of the smaller "males" in her web.
    I so hope that I get to see them leave the web..on little silk threads! Would feel very lucky to witness that.
    Am interested in the common house spiders you mention. Where do they spin their webs?
    The other spiders we have a few of this year is the St Andrews Cross Spiders. Beautiful spiders to look at.
    It's raining heavily here tonight and my black house does not like it!! She retreats into her funnel and calls her babies in with her.

  6. Thank you again for your comments. Wonderful to hear and exchange. I have just added a blog about the common house spiders - hope that means you will locate some and exchange chatter.

  7. Hi Lynne, well all my babies but 2 are gone now and every day I go to the shower to watch but miss them so. Actually there is the 2 still in the web, although further out to the edges, and there is also a couple that have moved to webs very close by. Mum looks kinda lonely and while I know that saying that is putting human values on her experience of life, I can't help but think it. I wonder will she have any more young. I have another female that i've been watching as well, although she is alot more cunning and doesn't very often let me see her.
    She has eggs at the moment and I eagerly await their hatching.

  8. Also, have been looking out for one of the American house spiders that you mentioned and have not seen a single one! Where would I be likely to find one?

  9. Hi wolfatron,

    Mum spider isn't lonely. If her young stayed, she'd probably eat them. Or they would eat each other. I am intrigued that you noticed the different behaviour between two individuals of the same species - one much shier than the other. I didn't believe myself when I first observed different personalities, but over the years I have found individuals to be so consistent in their behaviour, even though they differ from others of the same species, that I now know it is the case. Spiders have individual personalities. David Attenborough commented on his observation of the same thing when trying to film six spiders of the same species - he said it was the most surprising outcome from filming Life in the Undergrowth.

    Isn't watching them wonderful?

    As for the house spiders, they are hard to see until you realise that you have been staring at what looked like an empty web and that they are there. Their long legs are so pale that they blend into the web. The most common places are along window sills, and underneath them, or under the wooden frame which separates window panes. They have large tangle webs, just like redbacks. Much larger than you would credit for a little spider. The other place I find them very reliably are under eaves of houses. They will often build a web lat against the ceiling of the eaves and live on it. The easiest time to see them is when they are surrounded by a hundred little dots which turn out to be babies. The babies stay with them for a week or two.

    Once you have found them, then you will find them all over the place. It's just realising that the small whitish ball in the messy web - especially if there is an egg sac - is a spider. I don't know where you live, but around Melbourne I can find them on any building as long as the webs aren't scrupulously removed.

  10. Oh, and apologies for the delay in replying. We are moving in 7 weeks - to Castlemaine - and life did one of its smother-time episodes.

  11. Well, more interesting stuff going on with these spiders! My first girl (I'm going to have to follow suit with other spider watchers and name mine soon!) had a new small "batch" of spiderlings hatch, only about a week after the others had left. Indeed, not all the others have left yet, there are still two or three hanging around the web on the outskirts. Amazing..could not believe it when I went in and saw them.
    With regard to behaviours..I have also been watching yet another of these spiders, a third. She is totally unlike either of my other two. She doesn't care less how close I get to her, she comes out on her web every night and just sits there while I photograph her. She endures the flash and all sorts of banging on the window frame and even on the glass she has her web on. she'll let me up really close (1-2 inches) and just never runs into her funnel. My others won't let me near them..they dash off the minute anything disturbs them in the slightest. V different indeed:)
    Have spied some of the messy webs around that you mentioned. Thought they were Badumna Insignis actually. Must keep an eye out. I live around Melbourne so should be able to spot one. Have been looking for a wolf spider or Melbourne luck though.
    Have lots and lots of spiders that sit in a curled leaf in the middle of their webs during the day in our garden. Am yet to get a good look at one of them, they run back as soon as you shine a light on them at night..sneaky!
    Hope your move is not too stressy.
    PS. My partner bought your book for me the other day as he knows that I've been watching the spiders around our house alot lately. He didn't know that I'd been watching your
    blogg though. Lots of great info. Loving it.

  12. I am delighted that you have discovered the fun of spider watching - and that there is always something new going on once you get to know the individuals. Your third (I need names to distinguish them!) is just like my Legless - my favourite spider of all time. She would let me get as close as I liked, until the incident with the white-tailed. It's all in the book.

    I also had babies hatch in two lots from one of the Badumna webs this year. It was Little Birdski She landed on a bird statue inside the house when she was tiny and I watched her grow there. When she made an egg sac, I figured that she (and her statue) had better go outside - a house full of black house spiders didn't appeal. That was last season. This season she made two egg sacs, about a week apart. They hatched about a week apart. She made them in a location that I could just see them both. I wonder if yours was a second season spider. I don't think they last longer than that. Little Birski had to be moved before we sold the house, so I'll have to start with the new ones at Castlemaine to see if any get to a third season. None here have so far.

    Except for my trapdoors, of course. A few of them I have been watching for six years now, and they are full grown, so probably ten years old at least. They can live for decades.

    I noticed a lot of leaf-curlers in Melbourne last week. I haven't got any here. They are very cute. The males co-habit with the females, and sometimes you can see two pairs of legs sticking out from the leaf when they are both in residence. If you want to send me photos, I'll blog about them. Wish I had them here.

    I am really looking forward to your continued observations.

  13. I've got lots and lots of the leaf curlers here and yes, they all have a pair of reddish coloured legs poking if indeed some poor occupant is being squeezed out of their home! I will try to get some photos and send them to you.
    My second lot of badumna babies is starting to leave the web this week. I too wonder how old my first spider is. I think she was actually quite mature when she first caught my attention.
    Did you read my last entry under your "garden orb weavers - an amazing coincidence" story? Have you got any ideas? That beautiful spider is still missing in action I'm afraid.
    Ha! :) I must say, I've been getting some interesting looks as I read your book on the train on the way to work each morning!

  14. I'd love some leaf curler photos. I never seem to have a camera with me when I see them. They are unique to Australia. Aren't the Badumna babies cute? Have you seen any raise their little bottoms in the air, release their silk and take off?

    I did see the other message, and reply, but clearly I goofed and it didn't appear. I have replied again.

    I am greatly amused by the strange looks you are getting. One thing every author hopes will happen is that they will see someone reading their book on the train. It hasn't happened to me yet, but at least I know it is happening. Thank you!

  15. Hey Lynne, check out my new blogs at

  16. oops.. anyway, I have loaded a whole heap of photos for you to have a look at. I haven't seen any babies raise their bottoms. I thought they might today as it seems a great day with a gentle breeze etc.
    There are some leaf curler photos up as well..hard to get good ones of them!

  17. WONDERFUL to have another spiderblogger. I've pointed to it from facebook. I really hope that we might be the start of a trend. Change the world - eight legs at a time.

  18. Hi
    Just wondering if you have any suggestions on to relocate a female black house spider over my front door? she's just had a bunch of babies, she's a bit too close for comfort gotta go but don't want to hurt her.
    thanks Cherry

  19. HI Cherry,

    She will stay with her web if possible. We moved some by slowly rolling up the web on the end of a fairly long stick and she went with it onto the stick. Then put the stick down near an outbuilding or some other suitable location. I won't guarantee it will work, but my husband did about 20 that way when we had to clean up the last house to sell it. I just cried. I'd known some of them since they were spiderlings and didn't want to leave them. But we had to sell and not everyone likes spiders by the hundred on the back verandah and all over the doors!

    Good luck - it's so good to hear from someone who cares about hurting a spider.


  20. Interesting blog. Perhaps you can help me...

    I have one these spiders (like Gutsy from the first photo) in my house right now. She's been here for about a month so I decided to see what I could learn about her. I found out she can be poisonous (I have no intention of messing with her so that shouldn't be an issue) and I found out these spiders live primarily in Australia and New Zealand. My question is do these spiders live anywhere else in the world? The spider in my bathroom looks exactly like the one in your photo, the facial features, the leg structure, the coloring...everything exactly like yours, but I am in Florida - USA a long way from Aus or NZ. I can send you a picture if you would like. Do you know if they are common in the US or do I have just have a rare visitor?


  21. Black house spiders - any of our Badumna family, are native to Australia and NZ, but some of the smaller cousin of the black house spider, Badumna longinqua, have made it to the US. They are very hard to distinguish from each other except with adult females. I'd love to see any photos. If you are sending them, can you include the web. SOmetimes that can help distinguish. Send them to my email address: lynne @ without the spaces. If it is Badumna, then you have a rare visitor, although I think there was a population established in California.

    I watch them every night, so a good photo should help me know if it is at least possible that is what you have. Living in houses is quite usual. I'm looking forward to hearing from you!