Spider update

All I want for Christmas is another egg sac, and they aren’t obliging.

  • Vera ate another husband. Again. She’s the voracious jaws of death, and all I can hope for is that the poor doomed fellow inseminated her before getting sucked dry. Vera is hugely bloated right now, having consumed a large male and a smorgasbord of flies.
  • The other pairs of spiders are much more placid and are coexisting well, but no eggs yet. I did notice that one of them had molted, so maybe they’re too young? Have I set up a Blue Lagoon scenario here?
  • All of the spiders (except those sacrificed to the bloodthirsty Vera) are looking healthy and active, and are quite swift in demolishing flies presented to them.

So I’m just waiting. Waiting waiting waiting. Don’t they realize I’ve got plans for their progeny?

Now thinking about starting up a dairy spider farm on the prairies of Minnesota

There are these weird salticid spiders that have evolved a radically different morphology — they live in ant nests, and physically mimic the ants. Look at this ant-spider. Isn’t this amazing enough?

That’s a spider? Yeah, count the legs. It’s trying so hard to fit in with tunnel-dwelling insects with three body segments, you just have to applaud the effort.

What’s more, they’ve acquired another evolutionary novelty: they secrete ‘milk’ to feed their young, and have extended parental care. The necessity of milk production was tested with the cruel experiment of painting over the epigastric furrow (the site of secretion) with White-Out, and what happened? All the spiderlings starved to death. The utter bastards. There are things you can get away with when working with invertebrates that you couldn’t do with cute fuzzies with bones. Try doing that experiment with bunnies, just be prepared for torches and pitchforks.

There’s another revelation in this figure caption.

Spider milk and its secretion site in Toxeus magnus.

(A) Ventral view of mother. (B) Milk droplets secreted after slight finger pressure on abdomen.

Did you get that? They are milking spiders. I come from a long line of Norwegian dairy farmers in Minnesota, so you can guess where my mind went from here. Can I get state and federal subsidies for my spider farm? I’ll have to look into it.

The study is primarily about the life history of this spider species, with some experimental manipulation, and it does a thorough job of that.

T. magnus offspring body length growth and food resources during development.
(A) Egg hatching. (B) Absolute milk dependence: Spiderlings do not leave the nest, and the mother releases milk droplets to the nest internal surface. (C) Spiderlings forage during the day and suck milk at night. (D) Subadults nutritionally independent but still return to nest. (E) Spiderlings reach sexual maturity, but some stay with the mother. *The mother. N = 207 offspring, Nnest = 19 surveyed nests, error bars (SEM).

It’s missing one thing, though: any analysis of the chemical make-up of spider milk. I’m going to take a wild guess that unlike mammal milk, which is rich in fats and carbohydrates, spider milk is going to be more like a protein shake — that it’s going to be in many ways similar in composition to the dissolved bug guts that spider adults live on, to simplify the transition from an independent hunting spiderling to a spiderling with an obligate dependency on parental care. Which means a) humans can probably synthesize it by homogenizing masses of fruit flies in a blender with some digestive enzymes, and filtering out the chitin, and b) there’s not going to be much of a human market for it. Alternatively, they suggest that spider milk may have evolved from the breakdown of trophic eggs — that is, eggs produced that do not develop, but provide a food source for other members of the brood. In that case, it may be a soup of phospholipoglycoproteins, similar to the vitellogenins of other arthropods, and its closest vertebrate analog would be egg yolks.

Inquiring minds want to know. They’re going to have to milk a lot of spiders to get enough to analyze, though!


Chen Z, Corlett RT, et al. (2018) Prolonged milk provisioning in a jumping spider. Science 362(6418):1052-1055. DOI: 10.1126/science.aat3692

P.S. There is a Minnesota milk song. They might have to change some of the hand gestures.

Spiders will just break your heart

Last Wednesday, I was so optimistic. I’d paired up Vera with a first-generation son of Gwyneth (GI-♂), they’d gone at it hot and heavy, and had produced an egg sac — an egg sac with a peculiarity I’ll get to in a moment. My plan was to go in today and open up the sac and see what embryos I’d find.

The peculiarity was that although I’d classified all my spiders as Parasteatoda tepidariorum, there was still a little uncertainty. The patterns of pigment on their cuticles were a bit ambiguous. Here’s part of the description of P. tepidariorum from Common Spiders of North America.

This is a medium-sized to large cobweb weaver. The abdomen appears teardrop shaped as the spider hangs updide down in its web, spinnerets uppermost. The cephalothorax is tan or brown. The abdomen color is extremely variable, usually shades of light brown with a mottled tan or brown. Some individuals are nearly black, others unmarked and pale. The legs are darker at the joints.

The egg cases of this spider are tan and tardrop-shaped, point uppermost.

This describes my spiders perfectly, given that there is variability in the patterning of the abdomen. They look different, which had me worried that I may have gathered a couple of different species, but then the description of the egg case settled it for me: Gwyneth had produced lovely tan, teardrop-shaped egg cases. Case closed, right? Gwyneth and her progeny were P. tepidariorum.

Then Vera produced an egg sac. Vera herself also fits that description of P. tepidariorum to a T.

But the egg sac she produced was a cottony, pure white ball. What? I flipped through my books looking for some indication of what this might mean, and found a description of Steatoda triangulosa, which is also common in this part of the country.

This is a medium-sized cobweb weaver. The cephalothorax is reddish brown. The legs are light brown with dark brown bands. The apdomen is light brown with two rows of angular spots or bands of dark reddish brown separated by white areas with a mottled appearance. In some individuals this pattern looks checkered.

The egg case is a fluffy white sphere.

Uh-oh. Are Vera and Gwyneth from two different genera? There’s nothing in Vera’s abdominal pattern that fits S. triangulosa, but maybe that’s highly variable in this species, too, and the egg case definitely fits this description. But she’d bred with P. tepidariorum! Were the new eggs hybrids? Was I just a terrible ignorant klutz playing the taxonomy game poorly? I went into the lab to take a few steps towards finding out.

And…disappointment. The “fluffy white sphere” was gone — it had been torn apart. The eggs within were dried up lumps. Uncertainty reigns.

I put the two lousy parents into a petri dish and made a video. You look and tell me: Parasteatoda tepidariorum or Steatoda triangulosa? Looking at just the adult morphology, I’m saying P. tepidariorum, but what do I know. Video below the fold, with an agitated pair of spiders scurrying about.

[Read more…]

Happy Spider Report: Vera was preggers!

It’s all good news. All the spiders are thriving right now, chowing down on flies. Vera produced a very pretty egg sac — I’m thinking the 14/10 light/dark cycle may have something to do with it — and has shrunk to about half her previous size. I’m planning to open up the sac on Sunday as part of my devotional, just to check on the health of her embryos. Although I’m low on adults, the next generation is coming along, and with any luck I’ll have a swarm of spiderlings this time next week.

Crickets are bad, mmm-kay?

Disaster struck this weekend. I gave my fully-grown, big ol’ adult spiders crickets to eat. Now Vera is a monster: she just ropes ’em up, immobilizes them fully, and then bites them. So I was overconfident and gave crickets of the same size to Amanda and Xena.

The next day, Vera is a huge bloated sack of bug juice and her cricket is in fragments. Amanda and Xena are gone, and their crickets are sitting there smug and happy. Turns out crickets defend themselves by kicking predators, and poor Amanda and Xena were beaten to death and then eaten by the evil Gryllidae. This does not make me happy. I’ve got to find a safer food source. For now, I’m just giving the juveniles and the sole survivor lots of fruit flies. Death to all crickets!

In other spider news, I’ve been frustrated by the fact that none of them are producing eggs right now, and all the wild specimens have vanished from their usual haunts as winter descends upon us. Then, last night, I woke up in the wee hours with a sudden obvious thought.

Remember that movie, Silent Running?

There’s this scene where the space-going ecologist is concerned about how all the trees are losing their leaves, which are turning brown and falling off, and he hits the books trying to figure out what disease is killing his forests. And then he suddenly realizes, oh, autumn, seasons changing, all that, and I’m sitting in the audience thinking, you dope, of course, so he runs around setting up lights to create a growing season in the space domes. Yeah, I’m also a dope who didn’t think of that, and I should have, because I’ve got timers and lights for my fish rigged to put them on a 14/10 light/dark cycle. This is routine lab animal maintenance. D’oh!

So now I’m going into the lab this morning to put up lights and trick the spider colony into thinking it’s Spring, and time for love, by wiring up the incubator.

Vera is a beast

Today was cricket-feeding day. I am still learning things, and one of the things I have learned is that I hate crickets, those jumpy, twitchy, annoying little beasts. I have to struggle to confine and catch the things, but I chortle evilly when I finally slide them down into a vial. They’re two or 3 times larger than my spiders, but it’s no contest. They’re doooooomed. Bwahahahaha!

Also, spiders have personalities. Amanda is shy; she gets a cricket, she ignores it, and me, and just hangs out in her corner placidly until I leave the room.The cricket will be dismantled fragments the next day, but a lady does not make a spectacle of her murders.

Xena is timid. She notices the cricket for sure, but she runs away — where it is, she is not, and she scurries about rather frantically to avoid it. She lays down lots of webbing, though, and I think she waits until it snares itself thoroughly before going in for the kill.

Vera is a beast. Put anything in there, she does not delay sinking her fangs into it. I’d just put the cricket in her vial when she charged up, lassoed its hind limbs, and was making quick bites into the leg joints. She reminds me of Gwyneth, a real killer. Especially that bit about first knee-capping her prey before getting into the serious business of liquefying its guts.

Vera also escaped, briefly, and marched up onto my hand and stood there, gently tapping on my knuckle like she was getting impatient. Once the cricket was in her vial, though, she quickly rappelled down and made short work of it.

I’ve got to get them some mates, but I’m worried that the juvenile males are just too small — I may try tomorrow, though, when the females are fat and sated with cricket juice and might be willing to tolerate a conjugal visit. I’ve got a son of Gwyneth I’d like to pair up with Vera — what beautifully voracious slayers their progeny might make!

(I might be getting a little too close with my arachnid brood, I willingly confess.)

Spider poop

As promised threatened, I took some photos of spider poop this morning. It’s surprisingly colorful! But then, these are from the spiderling vials, so maybe it’s like baby poop, which also tends to have surprising colors.

The big circular feature is an artifact at the bottom of the plastic vial.

This is my masterpiece: I call it “Still life with spider poop, molted cuticle, and little blue bits of dried fly medium”. I’m thinking of printing it out on a 10 foot wide sheet and selling it to MOMA.

Spider Update: Cleaning day (no photos)

I’ve concluded that I’ve been a terrible spider daddy. What else can you say when your young spiderlings have a 90% mortality rate? I expect ICE to pound on my door any day now and give me an offer of employment at one of their detention centers.

In my defense, I am learning. My big mistake was hoping that I could keep a freshly-hatched clutch of spiderlings together for a fairly long period of time, to minimize the maintenance chores. Nope. Doesn’t work. I even did some quick experiments where I’d put small groups of 3 in vials of different volumes, so different population densities, and it didn’t help. After a while, there would be only one.

I don’t know whether it was simply that one would hog all the food, starving the others, or whether it was outright siblicide, but lesson learned: the babies get separated, day one. I just have to get a new egg sac first. Unfortunately, all I’ve got now are 3 full grown adults, and they’re all females (it’s their own damn fault, too, since they ate their husbands).

Today was cleaning day and sorting out all the juveniles. At this point, I have a grand total of…11 young’uns. They all look healthy and I don’t expect serious mortality issues from this point on. About a quarter of them are male (you will say, “what’s 25% of 11?”, and I will reply that one of them is ambiguously sexed at this point, with palps that aren’t quite fully developed), but I can’t use them to breed with the adult females, yet. It’s not a worry about incest, but just that they’re roughly 1/4 to 1/2 the size of the adult behemoths, and they’re too preciously few to risk turning them into snacks.

Speaking of incest, 82% of the juveniles are children of the dearly departed Gwyneth, so there goes genetic diversity already. That may not be a bad thing, given that Gwyneth was an uber-fertile monster queen, and a little inbreeding to reduce genetic diversity is useful in a lab model. I’m also planning to do some collecting trips this Spring, to get individuals who didn’t all come from one house on one corner of one block in Morris, Minnesota.

Anyway, right now they’re all tucked into fresh new clean vials, given a little spritz of water vapor, and a couple of hapless fruit flies each. They just need to grow now. Also, I have a sink full of dirty vials to wash out tomorrow. Spider poop, yuck.

Hey, maybe tomorrow I should take some pictures of spider poop — I suspect most of you haven’t seen it.

A quick spider update (no photos)

The last time I mentioned my spider work, I had sad news: the eggs were dreadfully dessicated, and I hypothesized that the declining humidity was not good for their health. I have no new egg sacs, but I did increase the humidity in the incubator, and have other good signs to report. There has been zero mortality among the juveniles this week, and the adults were extraordinarily lively — so lively that I had to deal with 3 escapes while I was trying to feed them.

I had spiders crawling all over me, which was a delightful feeling, but also made me a little panicky — I had to get them back into their nice safe vials before they got injured. All were rescued, no harm done, and they also immediately chowed down on the juicy flies I’d given them.

I felt all paternal and warm inside, as one does when dealing with affectionate pets.

A bad day in the spider lab

I had such high hopes this morning — necessary reagent had arrived, I had a nice egg sac, I was going to open it up and spend my afternoon exploring embryos. It was not to be. I teased apart the egg sac, and what do I find? Heartbreak. Disappointment. Failure.

The eggs were all dead. I’m not sure what happened here, but I have a hypothesis: this summer and early fall, I had all these fish tanks in the lab, gurgling away, and the place was pretty humid. Now those are shut down, and it’s winter in Minnesota, when the air dries out. Spiders like some degree of humidity, and I’ve been maintaining that by regularly misting their vials with an atomizer, but maybe that’s not enough for the embryos.

So I’m cranking up the moisture levels in the incubator. Now I’ve got to worry about balancing everything — too much and I’ll have to worry about mold and fungus.

Babies are such fussy little creatures.