Signs of Spring (spider edition)

It’s an unboxing video! I hear those are popular. Only what I’m unboxing is a pair of spider egg cases.

Spoiler: I don’t find any spiderlings inside. I find evidence of them being there, in bits of molted cuticles, but nothing was moving. I’ll let them warm up for a few days and look again.

If you want to know more about how spiders overwinter, here’s a source:

Tanaka K (1997) Evolutionary Relationship between Diapause and Cold Hardiness in the House Spider, Achaearanea tepidariorum (Araneae: Theridiidae). Journal of Insect Physiology 43(3):271-274.

The relationship between diapause and cold hardiness of the house spider, Achaearanea tepidariorum, differed geographically. In a cool-temperate population, enhanced chilling tolerance and supercooling ability were observed in diapause individuals, whereas a subtropical population showed only chilling tolerance. Because this spider is considered to be of tropical origin, it would follow that the ancestral diapause of this spider was equipped with chilling tolerance, but not with an increased supercooling ability. It seems that the ability to lower the supercooling point evolved through natural selection in the course of expansion of this species to the northern climates.

Now I have an excuse to visit Florida on a collecting trip, to gather representatives of southern populations. Maybe I should go in, like, February.

One other thought I had about the barrenness of these egg cases: it’s like the Donner expedition. Maybe one of the ways spiderlings survive the long cold winter is by eating their siblings, and this winter was particularly harsh.

Baltimore is a lovely place to visit, a real arachnotopia

Especially with this new attraction, An Immense Concentration of Orb-Weaving Spiders With Communal Webbing in a Man-Made Structural Habitat. You had me at “Immense Concentration”, but then they doubled down with “extreme spider situation”.

In late October, 2009, the managers of the Back River Wastewater Treatment Plant in Baltimore, MD sought assistance in mitigating what they described as an “extreme spider situation” in their sand filtration facility. The building, consisting of almost 4 acres (16,099m2) under a single roof but with no side walls, had been prone to extensive colonization by orb-weaving spiders since its construction in 1993. However, the present infestation was considered worse than normal, and the facility’s maintenance and operations personnel had voiced concerns over the potential risk of bites.

OK, I’m already gurgling with anticipation, but then the article is full of photos and graphic details about the magnitude of the webbing. It is amazing and beautiful. They used the volume of webbing and density of spiders to estimate the total population in this building.

Over 100 million spiders! And just yesterday I reported counting 63 in my garage. I feel so inadequate.

I said there were photos. Behold and be awed.

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Spider Update

It’s been a while since I had anything new to report — the colony is just sitting there, waiting for me to provide the ladies with some males, since they ate all of them. But we’re gearing up for a field season, so there were a few things I was able to try.

I’ve written up a protocol for our summer spider survey. It’s mainly a series of steps we’re going to carry out as we scan a garage, because consistency is important. We’re not going to be able to see every spider in every place — they’re sneaky, quiet little buggers — so we need to survey each environment in the same way, so that we can compare the residences, even if we know we’re going to miss animals. So Mary and I put on headlamps, plunged into our frigid garage and went through the motions to see how practical my plan was.

We didn’t expect much. It’s been a hard winter, and while today felt much warmer and the snow is melting, it really is still only 2°C, hardly happy weather for spiders, and not any better for their prey. We went spider hunting anyway.

As expected, there wasn’t much alive out there, maybe. The only spiders we saw were cellar spiders, Pholcidae, and they didn’t seem to be up to much. In fact, they might have all been dead. They were all inert and unresponsive to touch, but were still strangely plump and life-like, if still. They could be little frozen corpsicles, or possibly estivating. We couldn’t tell. We counted them anyway, if they looked intact and like, maybe, they’re going to rise from the dead at some point. It was all practicing the protocol, anyway.

The end result is that our cold and unpleasant and rather cluttered garage, 5.3m wide and 6.1m deep, has walls that are all covered with cobwebs, especially any part of the wall that is more than just a bare surface. If there was so much as a nail sticking out of a sheet of fiberboard, there was a cobweb on it. We counted a total of 63 zombie pholcids in that little space, and also found 11 egg cases of at least 3 different types. We’re starting to think our biggest challenge will be counting all the spiders in a reasonable amount of time once summer arrives with the mosquito season and the happy little beasts start fornicating fiercely.

One neat little surprise: along a back wall, there’s an area with a rack of shallow shelves, and Mary excitedly tells me that she has discovered spiderlings! I was skeptical and thought that was metabolically improbable given the ambient temperatures, but when I looked, sure enough, there were sheets of webbing in all of those shelves, and in all of them there was an explosion of tiny white dots with itty-bitty hairlike protrusions. They were of the right size, and that was the kind of scattering I’ve seen in newly hatched spiders in the lab, but I couldn’t imagine they might have survived a Minnesota winter, and they didn’t.

I twirled a patch of cobweb with the putative spiderlings onto a brush, and brought it into the lab, and sure enough…spiderlings. Well, the molted cuticles of many adorable baby spiders. Here’s a photo.

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The perfect metaphorical image for spider taxonomy

One of the things I’ve been struggling with this past year has been spider systematics, and it has been frustrating. If I see one more taxonomic revision, I’m going to gag; every attempt to assemble a coherent picture of their evolution seems to be fragile and ready to fall apart. I don’t blame the scientists doing the work, I blame the spiders themselves for being diverse and complex.

However, I have never seen a diagram that so aptly illustrates the chaos of spider phylogeny unironically.

Schema of spider web evolution. A selection of orb web on a tree to demonstrate the various web types—this is certainly not a phylogenetic tree. Distant ancestors such as scorpions and more close ones such as mygalomorphs and ctenizids roam the ground, already using silk to line burrows and construct trip-lines. Further ancestral relatives (e.g., Eresus and Agelena) build their webs on the base of vegetation; a Dictyna web spans the fork of the tree. The right-hand branch contains (in order from its base) the webs of Stegodyphus, Uloborus, Hypotiotes, Deinopis, and Miagrammopes. The center branch holds a two-dimensional araneid orb web by Araneus. The left-hand branch holds a two-dimensional tetragnathid orb web by Meta. This branch also supports (upper left to right) derived orb webs by Theridiosoma and Scoloderus, and the minimalist Mastophora glue-drop web as well as (below on the extreme left) the highly derived three-dimensional webs by Achaearanea and Linyphia (adapted from Vollrath F. 1988. Untangling the spider’s web. Trend. Ecol. Evol. 3:331–35).

Whoa. It’s a schema of spider web evolution that is “certainly not a phylogenetic tree”. OK, what is a “schema” then? You’re using a tree structure as part of an explanatory framework, but the webs are drawn between the branches. How does that work, exactly? How am I supposed to interpret this diagram? What relationships are being elucidated? Am I just too old to be learning new stuff?

Why are there volcanoes erupting in the background?

Otherwise, it’s an informative paper. I’m beginning to think of some of their diagrams as an analogue to how Spider-Man will splat a blob of webbing in a bad guy’s face to shut him up or blind him.

I’m definitely going to have to go to the American Arachnological Society Meeting this year in June, just to hang about with some arachnologists and maybe absorb their attitude by osmosis or something, because I’m mainly just confused.

An inspirational story?

I was reading about Greta Binford, the spider-woman, and there’s a lot of good stuff here. I was a tiny bit put off by this bit, though:

Binford came late to the study of spiders, and without morbid predilections. She grew up on a small corn- and-soybean farm in west-central Indiana—“dull spider country,” she calls it.

I’m afraid Minnesota might be even duller spider country, and I’m a bit concerned about the lethality of our winters — it might be a very seasonal spider country. But that doesn’t make them less interesting. I’ve already got some ideas for experiments to test mechanisms our local populations have for coping. Also, even in winter I’m finding lots of spiders indoors, just not the species I was focusing on.

Binford is forgiven, though. She’s most interested in spider venoms, and that’s not a particular strength of upper midwestern spiders. I’m more into development and behavior, so there’s plenty to keep me occupied here.

But this bit rings true, for sure.

The key to good hunting, Binford said, was to have a “search image” in mind. Wolf spiders, for instance, can be found by their eye shine. When you train a flashlight beam over your back yard at night and see a faint glimmering in the grass, those might be spiders gazing back at you. Loxosceles tend to splay their legs like asterisks, and to gather in pockets of dampness—anything from the bottoms of rotting logs to the spaces behind steam pipes. “It reminds me of hunting for morels as a kid,” Binford said. “There’s a kind of Zen moment where everything falls away and there’s just you and the spider.”

The stairs led down to a long, open space, with pipes and wires hung low from the ceiling. Bits of graffiti flared into view, as our headlamps swung past, and strands of webbing caught at our faces. Most of it belonged to pholcids, or daddy longlegs, Binford assured me. Their venom is strong enough to kill a mouse, and they prey on other spiders, but their fangs are too small to hurt us. She played her beam along the bottom of a wall and held it on a Steatoda, a bulbous relative of the black widow, famous among arachnologists for turning radioactive and biting Peter Parker in the recent Spider-Man film. Then she stopped and scanned the room from end to end. “It’s like an Easter-egg hunt,” she said. The spiders were hiding in plain view.

I’ve experienced the same phenomenon! I’ve been walking these halls for years, totally oblivious to spiders, and now that I’ve started seeking them out, they’re everywhere! I find myself looking in corners, and window frames, and crevices, spotting cobwebs or fragments of chitin, and tracking down these little guys who share our homes and office buildings. If you’re an arachnophobe, I recommend not ever looking for them, or you’ll start spotting your nightmares all around you. Don’t develop that search image in the first place.

But don’t worry.

Spiders have a bad reputation, largely undeserved. The great majority aren’t venomous enough to harm us, or their fangs are too small, or their jaw muscles are too puny, or they simply see no profit in attacking large, indigestible creatures that can crush them with their toes. Unlike snake venom, which is designed to kill vertebrates, spider venom is almost always meant for insects. Its toxins can stop a hornet in mid-flight, but they lack proper targets in the human nervous system. “If we were wired for spider venoms the way insects are, we would be screwed,” Binford says.

She is studying Loxosceles laeta, a more potently venomous relative of the infamous brown recluse, which is infesting a Goodwill building in Los Angeles. I don’t know if you’ll find this part of the story reassuring.

When Binford milks laeta in her lab, their fangs yield about ten times as much venom as other Loxosceles’, and medical records suggest that their bites leave larger lesions. Yet, even if the Goodwill’s population spread across Los Angeles, it isn’t clear how much of a threat these spiders would pose. Laeta are easily as reclusive as their North American cousins. They keep to dark, quiet areas and shrink from human contact. When they do bite, the venom doesn’t always have an effect: some people’s immune systems aren’t sensitive to Loxosceles toxins. Five years ago in Lenexa, Kansas, a family of four trapped and killed more than two thousand recluses in their nineteenth-century farmhouse. Yet no one in the family suffered from a bite.

I would love to find a building with thousands of recluses lurking in it, but it’s not likely. They don’t seem to have taken to living this far north. But this might be one of the advantages of climate change, you never know.

True Facts about the bolas spider

This is funny, but I have never seen a bolas spider. Have you?

They’re on the checklist of Minnesota spiders, though, so they exist this far north. I’m going to have to make finding one an objective of my summer research plans. They’re nocturnal, though — I might turn into that weird guy poking around in the neighborhood bushes and trees late at night. I swear, officer, I’m not a peeping tom, I’m just looking for arachnids.

Hmm, the cemetery might be a safe place for nocturnal spider watching.

Paratropis, Stormtropis

I was just reading about these recently identified genera of Central and South American mygalomorph spiders, Paratropis and Stormtropis, and got a little thrill from the photos, so I had to share. Their eyes are mounted in a little turret-like structure bulging up above the cephalothorax, and when you flip them over, oooh, those fangs. All black and pointy.

I know some of you don’t get that excited about spiders, especially ones that hairy and weird-textured and equipped with especially prominent bitey gear, so I’ll hide them below the fold.

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They’re all lovely! Every one!

I should let you know about this article, The ultimate lovely legs competition: the world’s nine most beautiful spiders, although I’m not too thrilled with the premise. It’s not a competition, all spiders have lovely legs…and chelicerae and eyes and abdomens and cephalothoraxes.

(I didn’t include any photos in this post because I’ve learned that some of you get so overwhelmed by the beauty that you close your eyes or close the browser window and go have a nice lie-down, and I didn’t want to disturb your work flow.)

Good Morning Spider!

It’s Thursday, which means it’s my spider clean up day — feeding and removing withered dead corpses from their vials, and also bottle-washing and general tidying up.

I’ve also been working on compiling some resources for students, since in a few months I have to sit down with a few of them and teach them how to identify spiders (challenging, since I’m a novice myself). For everyone’s general edification, here’s a short list of websites with taxonomic information:

Of course I also have a couple of printed field guides. I’m eager for the spring thaw and an opportunity to go chase spiders.