The compost bins are coming alive!

I got word from a colleague* that their compost bin was accumulating spiders again — they had a swarm of them last spring, that disappeared over winter — so I had to check it out. I opened the bin and was disappointed at first, because while I saw lots of cobwebs all over the decaying vegetable matter, there was nowhere near the number of spiders I’d seen in the spring.

I finally spotted one in a corner. Steatoda borealis, the same species that had thoroughly colonized the bin before.

Steatoda borealis is an interesting theridiidid. They seem to be the native species to this area, with the more common house spiders being immigrants from either Eurasia or South America, depending on the species. These beasts are bigger than the others, and I haven’t seen them in houses or garages much, mainly outdoors or in special environments like this compost bin. I’ve got some in the lab, and they seem less active than Parasteatoda or Steatoda triangulosa, but that may be because I’ve only observed them in the day.

I spent several moments poking around in the bin, taking a bunch of photos, making a note to myself to come back in a week or two. Then I started to lower the lid. The lid I’d been holding up all this time with my left hand. Only then did I notice that it was covered in webbing, and there were all the spiders, lots of them, gettin’ busy busy beneath my oblivious fingertips. Squeee! Jackpot!

So I had to take a bunch more photos. These spiders were paired off all over the place, mating furiously! I took photos of these wonderful piles of tangled legs, 16 at a time with agitated bodies having a grand time.

You’ve probably heard about female spiders killing their mates and eating them, but that doesn’t happen so much in environments rich in food. Steatoda and Parasteatoda can happily coexist in sprawling web communities where lots of insect life is rising up from a festering mass, and they don’t do the cannibalism thing in those circumstances.

I did notice one lonely male off to the side of a mating pair, staring intensely. I hope you find your true love soon, little guy!

Definitely going back here later. It’s a wild little hotspot for spider orgies.

This post also appears on my Patreon account, complete with spider photos. The photos are also posted on Instagram and iNaturalist.

*A colleague in math. Curious fact: two of the professors in our math discipline have the most interesting spider populations in their yards. Is it something about mathematicians that attracts spiders?

Spider gluttony

I was checking out our compost bin, which is swarming with young juvenile spiders, and what jumped out at me was how fat they’re getting. These little spiders are growing fast and are turning into regular whales. This one, I noticed, had a secret stash — they’d corralled a bunch of baby isopods to snack on whenever they felt peckish.


Yum. All gathered into one spot, and tender and delicious nibbles, too. No wonder they’re getting so plump.

Personally, I’m feeling well satiated right now. I scheduled one class to turn in their final assignment last night, and another class to turn in their term papers tonight. I’d rather lick isopods off a compost bin lid than read any more student papers.

I want you to know this was a challenge

A swarm of Parasteatoda have hatched out in my compost bin, and I’ve tried a few times to get decent photos of them, but it’s hard. They’re young and tiny — less than half a millimeter long — and they’re busy, scampering all over to build webs, so shooting them is tough. Also, I’m rusty from a long winter neglecting my camera.

Here’s one being spooky, its cephalothorax in shadow with just the pair of posterior median eyes visible and glowing.

I’ll keep practicing and they’ll keep growing.

Spring is sprunging

It’s been raining off and on for the past week, and we have rain forecast for the next ten days, right up through commencement, and the trees have started vomiting up leaves.

You’ll notice even our bedraggled lawn is turning green.

Spring won’t actually be here until the grass spiders start putting up tents all over the yard. I’ve been watching a couple of places where I know Theridion always lurks, and have been seeing traces of silk; we also found a Parasteatoda building a cobweb in our compost bin. Once classes are over, it’ll be time to get down in the weeds and see who else is emerging.

Just another spring day on campus

Here is a typical gathering of UMM students, honoring the god of electricity.

UMN Morris is a clean energy leader and destination. We are carbon neutral in electricity. UMN Morris produces more clean electricity per student of any campus in the United States.
-100% carbon neutral electric status achieved in 2020
-1,000,000 lbs + of organic waste diverted from landfills by campus and community
composting program
-10 Million kWh electricity produced each year by two wind turbines
-Gold STAR rating (Association for the Advancement of Sustainability in Higher

Are spiders attracted to Sephora cosmetics?

I’m suddenly reading a viral anecdote all over the place — the claim that a “body butter” (whatever that is) called “Delícia Drench” and marketed by the cosmetics company, Sephora, attracts wolf spiders.

If you’re scared of wolf spiders- watch out for these lotions lol. I wanted to love them sooo bad, but one of the ingredients is like kryptonite to wolf spiders! When I put it on instantly one will come out. Normally I’ll see one every like 3 years, used this and it was every day. I stopped using it and haven’t seen one since…. oh and one time, the spider wanted to eat whatever ingredient it is so bad that it chased me. I swear on everything. I’d run left, it ran left, I ran right, it ran right. Like it was legit following the scent. And no, the scent isn’t that good, nothing a $5 vanilla cream can’t match. So yeah, do be careful if you’re frightened of spiders, especially the big wolf ones. Also, plz don’t hurt them if you do wear this & they appear. Use a cup and put them outside. Sorry for a disappointing review.

There are a few red flags here. It’s a negative review written by someone who apparently wants to discourage purchase of the product. It’s an account that says little more than that the writer noticed lots of spiders. I hate to tell you this, but I don’t use “body butter” and I can see swarms of wolf spiders in season — they’re ubiquitous and common. Wolf spiders scamper all over the place, they’re very active animals, so telling me that one seemed to be chasing you is unimpressive.

And that’s it. One anecdote. Why would anyone think it’s particularly interesting?

OK, then someone came up with a reasonable explanation for a particularly unsupported and unrepeated observation.

Hello. I just did a little dive into chemicals that attract spiders because I really don’t like bugs. Ao according to studies? There is a two component female produced pheromone of spider. It basically signals for sexual communication. The chemical analysis reveals that “farnesyl acetate, diisobutyl phthalate and hexadecyl acetate of the spider webs exhibited higher relative abundance in sexually receptive females” also, “Two choice behavioral essays verified that the blend of farnesyl acetate and hexadecyl acetate attracted males”.

Farnesyl acetate is primarily used in skincare for fragrance and same for Hexadecyl Acetate (cetyl acetate) for fruity smell and waxy appearance. Cetyle acetate is commonly used as a thickening agent for body cream and lotion.


Vaguely interesting. Spiders do a lot of chemical signaling, so finding that two common chemical signals are also present in the ingredient list of a beauty product does add the faintest patina of plausibility to the anecdote, which, I must add, has not been validated at all. I’m also dubious that a spider would find the the exact combination of these two chemicals on a surface at all appealing, and also not be thoroughly put off by all the other goop found in a product called “Delicia Drench.” It’s like suggesting that a dab of androstadienone, a putative human hormone, would make a compost heap irresistible to passing women.

I would need to see some actual empirical testing before I’d believe any of this. It’s possible but unlikely, and there’s no verified phenomenon that needs explanation. If I had some Delicia Drench in the house, I might test it in the spring — it would be easy, put a drop of the stuff in a cup at the bottom of a pit trap, and measure the frequency of wolf spiders caught relative to traps without the stuff. I’m just not interested enough to buy some Sephora gunk to see if it does anything.

Also, there’s no point: Sephora has rushed to claim that they have removed farnesyl acetate and hexadecyl acetate from their products!

I do not know if wolf spiders are actually sensitive to Delicia Drench, but I can at least say that capitalist corporations are extremely sensitive to rumors that might compromise profitability.

Please, everyone, learn to question tenuous claims that lack any empirical support!

Lesbian spiders? Dimorphic males? Precocious adolescents?

Yesterday, I set up a cage for Steatoda borealis. I haven’t successfully raised them in the lab, probably because I haven’t fine-tuned their environment, but I thought I’d give it another try. I caught these individuals living in a communal environment (my compost bin), so I made a substrate of moss, for burrowing in, and added 5 females, all in the same confined space.

I came in today, and what do I find? They’ve built a communal web and they’re all perched on it, spaced about 2cm apart. This is already interesting.

Something to know about S. borealis: the adult males are distinctive, they have palps that look like massive medieval instruments of war, while the females have slender palps. I was pretty confident I’d segregated them by sex accurately, on the basis of casual inspection.

So I added a male this morning. All the spiders seemed somewhat agitated, there was much scurrying and tapping and exploratory sensory behavior, as I would expect. The male was courting the biggest, plumpest female in the cage.
Then, to my immense surprise, two of the females (I think) paired off, and one of them was aggressively thrusting its skinny little palps at the others genitals. Whoa, what? Did I misgender them, or was this some kind of social behavior?
Then I get dragged away to attend some fucking meeting, and couldn’t inspect them more carefully. This was extremely annoying, as you might guess.

Now I’m intensely curious. I’ve searched the literature, there is no mention of male dimorphism in this species, but it’s an interesting possibility that warrants further investigation. The other possibility is female:female sexual behavior — these spiders are somewhat social compared to others I’m working with, so it could be some kind of bonding behavior? Another possibility is that I’m fooled by juvenile males that exhibit typical sexual behavior but just haven’t completed their final molt to acquire their gloriously developed sexual organs.

I’ll be putting them under the microscope tomorrow to find out.

What beast emerges from the dark depths?

This is exciting. I’ve written about my compost bin before, which has been a rich source of spider lore — a partially closed habitat, the domain of some large dark spiders that build their cobwebs in a place rife with buzzing insects.
The bin has been inaccessible for months, buried under snow. Today the snow had retreated enough that we could hobble over slick, crunchy ice to get to it and throw back the lid. What did I see?
First, fresh silk, new cobwebs laid across the corners. Somebody had been working hard. Then, suddenly, at one side, a massive spider loomed out of the darkness — a fully grown, adult male Steatoda borealis. His presence tells me something: he’s much too large to be a recent hatchling, so he must have overwintered down in the dark, sheltered from the storms, huddled in the fermenting warmth of the compost.
We closed the lid and let him be. I’m sure there are more down there who will creep out in the next few weeks to rebuild a thriving colony.

If you want to see this massive unit of a tough Minnesota spider, you can go to Patreon or Instagram. He’s big and dark in shades of red and black with thick strong limbs and glowing eyes.

There be spiders under there!

Beneath that huge pile of drifted and shoveled snow beside my garage lies buried my compost bin, legendary home to many generations of spiders (especially Steatoda borealis) and maggots. I couldn’t seen any spiders before the last big storm, but now I can’t even get to it. It’s completely covered in an avalanche of snow.

This is probably just fine for the occupants. Lots of spiders overwinter by snuggling down under the layers of snow, and others just tuck away an egg sac and let the embryos rest quietly until the spring. I’ll be checking in as soon as it melts and it warms up a bit more.