I want to see the mighty sex battles

Lately, I’ve been curious about this one species of spiders I’ve been breeding, Steatoda borealis. What makes them stand out compared to the other two species in the lab is the size of their palps — they’re significantly larger in S. borealis. It’s got me wondering why they have these massive spiky hooked medieval maces on their faces, where other species have prominent, distinctive bulbs but nothing of the magnitude of this one set of males.

Then I see this species of harvestmen that put my spiders to shame. Look at this gigantic apparatus on the animal’s head! It can be up to 50% of their body weight!

The surprised don’t end there. These harvestmen have three distinct kinds of males, alpha, beta, and gamma, all distinguishable by the morphology of their genitals, and then there are females, of course (only one flavor, though). So four sexes?

Intraspecific variation in the New Zealand harvestman Forsteropsalis pureora: (a) alpha male (major), (b) beta male (major) (c) gamma male (minor), and (d) female. The second cheliceral segment representative of alphas, betas, gammas, and females is shown underneath the corresponding in situ photograph. Scale bars indicate 1 mm.

So how did this state of affairs come about? Fighting. The males engage in combat to gain access to females. This is a familiar strategy — you’ve got the big bruisers who go straight into battle with their rivals, and while they’re thus engaged, you’ve got the gracile sneaker males who dart in and have sex. Those big genitals are costly and tactics that don’t require that kind of investment are advantageous. We’ve seen similar phenomena in beetles and squid.

Alpha and beta males can have a body mass up to seven times higher than that of gamma males, demonstrating the drastic intraspecific variation found in this species. Gamma males adopt a scrambling strategy, searching through their environment to find mates and avoiding contests with other males, while alpha and beta males use their exaggerated chelicerae as weapons in contests to access females.

Awesome. Now I’m thinking that maybe S. borealis exhibits a pattern of combat that has driven the evolution of more exaggerated genitals. It’s not the only possibility, though — the females of this species are also fairly large and powerfully built. So who’s fighting whom?

I may have an excuse to set up some cage matches in the lab.

Bless your beautiful hide!

My wife and I got together this morning and strolled over to the holy place — my lab. She’s been raising a few spiders of her own, and we brought them to the microscope to go “ooh” and “aah” over them and sex them. We ended up identifying 7 females and 7 males, which immediately brought to mind…

None of them were singing, fortunately, but we paired them up and set them up in nice housing with a little spritz of water and and a bunch of flies. We watched them for a bit, but unfortunately for our hopes for a little boom-chicka-wow-wow, the boys were kind of shy. We left them to a quiet night alone, and I’ll check on them in the morning. And remove any corpses, the standard service for any honeymoon suite.

The boys are all thinking about whether these are the brides for them right now.

No anthropophagy among spiders, yet. That we know of.

I thought you might want to know that Spiders feeding on vertebrates is more common and widespread than previously thought, geographically and taxonomically. Not that I want you to worry or anything, but you should know that vertebrates like you are prey to certain spiders. (Not you, personally, of course — just your smaller, weaker cousins.)

You might be wondering who the killer spiders are, and you’re in luck: here’s a table of the spider families that will kill your relatives.

Frequency distribution of 39 spider families engaged in vertebrate predation based on cummulative literature data (source: McCormick & Polis 1982; Brooks 2012; Nyffeler & Kno ̈rnschild 2013; Nyffeler & Pusey 2014; Nyffeler et al. 2017a, 2021; Nyffeler & Vetter 2018; Weisberger 2019; Nyffeler & Altig 2020; Reyes-Olivares et al. 2020; Fulgence et al. 2021; Nyffeler & Gibbons 2021, 2022; Google Scholar & Google Picture Survey for Sparassidae feeding on vertebrates 2021). The ten spider families Atracidae, Theridiidae, Pisauridae, Ctenidae, Theraphosidae, Nephilidae, Araneidae, Lycosidae, Sparassidae, and Trechaleidae are the most prominent vertebrate-eaters (combined 91% of a total of 966 recorded incidents). *The number of records for Atracidae (n 1⁄4 20) presented here is an underestimate [The atracid Hadronyche formidabilis must be considered to be a habitual frog-eater due to the fact that countless frog bones had been found in funnels of this species which not could be taken into account in this graph (McKeown 1952)].

See? No worries. You probably don’t even recognize most of those names.

I’m here to inform you that the number one culprit, the Theridiidae, also known as the tangle-web spiders or comb-footed spiders, are also among the most common house spiders. The spiders I raise in large numbers in the lab, the Steatodas and Parasteatodas and Latrodectus, all belong to this family, and I’ve long noted their ability to bring down animals much larger than themselves with their potent venom and most excellent cobwebs.

Not you, of course. You can continue to sleep well at night, knowing that the spiders living in your attic and basement are not going to eat you. Not unless they grow significantly larger, or form significant and numerous cooperative colonies.

My spiders do get along well with each other, so there are possibilities…

If you doubt me, here are some spiders eating birds, bats, frogs, fish, and snakes. Yum.

Examples of habitually vertebrate-eating spiders – A. Argiope aurantia Lucas, 1833 feeding on a female ruby throated hummingbird (Archilochus colubris) in front of a house in College Station, Texas (Photo by Donell S. Frank). B. Nephila pilipes (Fabricius, 1793) feeding on a small bat (superfamily Rhinolophoidea) entangled in the spider’s web; incident observed at the top of the Cockatoo Hill near Cape Tribulation, Queensland, Australia (Photo by Carmen Fabro). C. Megadolomedes australianus (L. Koch, 1865) (Pisauridae) feeding on a Graceful Tree Frog (Litoria gracilenta) in Barratt Creek, Queensland, Australia (Photo by Barbara Maslen ‘‘Wild Wings & Swampy Things Nature Refuge, Daintree’’). D. Adult male of Ancylometes sp.(possibly Ancylometes rufus (Walckenaer, 1837)) caught a characiform fish (Cyphocharax sp.) near Samona Lodge, Cuyabeno Wildlife Reserve, Ecuador (Photo by Ed Germain, Sydney). E. Adult female black widow (Latrodectus hesperus) feeding on a subadult coral snake Micruroides euryxanthus (Elapidae) near the Boyce Thompson Arboretum, Superior, Arizona, USA (Photo by Lawrence L. C. Jones).

But don’t worry, they aren’t eating people yet!

Nyffeler M, Gibbons JW (2022) Spiders feeding on vertebrates is more common and widespread than previously thought, geographically and taxonomically. Journal of Arachnology 50:121–134.

Learn to love your spiders!

Well, this is discouraging.

Scientists asked almost 1,800 people to rate 25 species of animals according to how much fear and disgust a photo of each one elicited. The spider got equally high rankings for both fear and disgust from more people than any other animal. The spider was also deemed the scariest and nearly the grossest as well.

I find myself snuggled up in the top right corner of that chart. No wonder nobody likes me.

But there are some words of hope.

Ecologist and self-proclaimed spider ambassador Bria Marty tested whether learning about spiders can change how people feel about them for her master’s thesis project at Texas State University in San Marcos. She recruited college students to find and identify spiders using an illustrated guide and then upload photos to iNaturalist. Marty, currently a PhD student at Texas A&M University-Corpus Christi, surveyed participants before and after the activity, and one thing jumped out: Afterwards, people reported being far less likely to react negatively to a spider. “Doing an activity like this really does help a lot around fear,” she says.

This kind of change has been known to happen to iNaturalist users, says Tony Iwane, the platform’s outreach and support coordinator and a self-described spider lover. He pointed me to a thread on the site’s discussion forum about how contributing to iNaturalist helped people overcome their fear of spiders, with users sharing the “gateway spider” species that changed how they felt. For @mira_l_b, it was the particularly tiny Salticid (jumping spider) species Talavera minuta. “If I am finding myself confronting life-long fears and cooing sweetly to tiny Salticidae,” she wrote, “then there’s hope for us all!”

The author is advocating a big spider counting exercise for everyone, which sounds like a good idea to me. Except this is not the best time of year for it — spiders are making themselves scarce right now, hiding from the winter onslaught, but you can still find lots of spiders in your houses.

So go find them and say hello!

Is Eric Hovind trying to provoke me?

He’s succeeding. He has this new series of videos titled “Beyond Darwin,” in which he tries to claim that fossils disprove evolution. It’s warmed-over Harun Yahya bullshit. You know, show a picture of a fossil, then show a picture of a modern animal, and declare, A-ha! There’s no difference between them!

It’s all perfectly ignorable nonsense, except he roused me from my slumber with this: SPIDERS DISPROVE EVOLUTION!

What a pitiful effort. Let’s scrutinize his example of failed evolution, shall we?

On the right, that’s a familiar beast: that’s a modern Araneus diadematus, or European garden spider, a big ol’ common orb weaver. It is most definitely a true spider.

On the left is a grainy photo of a fossil. It took me a moment to figure out what that is — you might look at it and notice that it seems to have only 6 legs. Actually, it has 8, but the 2nd pair is thin and attenuated. It also has a segmented abdomen, unlike most modern spiders, and there’s something going on with it’s mouthparts. It’s an arachnid all right, but it’s not a spider. That’s a fossil whip scorpion, Weygoldtina. Here’s a reconstruction that will clarify the details.

So here’s dumbass Hovind showing us a photo of two animals with radically different morphology, coming from two different distinct orders, the Araneae and the Amblypygi, and trying to tell us they look completely the same. Then he says Maybe evolution didn’t work on that one, or it just evolved as high as it can go, two excuses that aren’t valid evolutionary concepts. He riffs absurdly, pointing out that spiders still die, as if that’s something that wouldn’t happen under evolution.

Hey, Eric, does the fact that you’re still ignorant mean that education doesn’t exist? Do you think The Atlas of Creation is a biology textbook, rather than a religious scam written by a convicted con man? This approach didn’t work out so well for him, or your dad, you know.

I guess the rotting apple hasn’t fallen far from the dying corrupted tree, I guess.

Wait! I just watched the full video from Eric Hovind (the clip above is just an excerpt), and would you believe…he comes right out and cites The Atlas of Creation at the 21 minute mark and credits it for his ideas!

He is literally pulling out examples and photos from that discredited and blatantly silly book and quoting them as evidence that we have to move beyond Darwin. (Here’s a hint, Eric: we have. Darwin didn’t have genetics or molecular biology as tools.)

Sacrifices made in the name of lust

Some spiders have a serious problem: runaway evolution sometimes produces maladaptive conditions. Here’s a spider, Tidarren sisyphoides, that exhibits extreme sexual dimorphism — males have about 1% of the mass of the females.

Male and female T. sisyphoides in copula. The minute male (indicated by the arrow) on the female’s ventrum is ≈1% of the female’s mass. (The scale bar represents 1 mm.)

That’s not the problem, though. The problem is that the males maintain a massive pair of palps. Really gigantic. They probably clang when they walk. Look at these two big boys, and the monster intromittent organs dangling from the front of their faces.

You may notice that the top spider has the normal two palps, which are so large that they’re interfering with each other. The bottom spider has only one palp. The surprise is that this is a product of self-mutilation.

During copulation, males generally use both pedipalps in an alternating fashion to inseminate the paired spermathecae in the female. In Tidarren, however, one pedipalp is removed (either left or right pedipalp, seemingly at random) before sexual maturation which has also been described for another spider of similar size and closely related to Tidarren (Echinotheridion). Just after molting to the penultimate instar, the male secures one of its pedipalps to a silk scaffold and then twists it off by turning in circles and pushing the bulb with the third and fourth pairs of legs.

Ouch. There’s a reason for their partial emasculation, though.

We found that, for male Tidarren sisyphoides, maximum speed increased (44%) significantly and endurance increased (63%) significantly after pedipalp removal. Furthermore, spiders with one pedipalp moved approximately 300% greater distances before exhaustion and had a higher survival after exertion than those with two pedipalps. Removal of the pedipalp may have evolved in male Tidarren because of enhanced abilities to search for females (higher endurance and survival after exertion) and to out-compete rival males on the female’s web (higher maximum speed). Our data also highlight how the evolution of conflicts can result in the evolution of a novel behavior.

Not recommended for humans, unless your testicles are the size of basketballs.

Ramos M, Irschick DJ, Christenson TE (2004) Overcoming an evolutionary conflict: removal of a reproductive organ greatly increases locomotor performance. Proc Natl Acad Sci U S A 101(14):4883-7.

Summer research presentation time!

My students talked about their work today — this picture was taken before the crowds put them to work.

Violet took full advantage of the medium, a big screen connected to a laptop, and instead of a static display, the ‘poster’ rotated through a big collection of images. They had the prettiest poster of the group, as long as spiders are considered to belong to the category “pretty”.

MORE SPIDERS

I saw the mommy spider spin the egg sac on 21 August, and this morning, the 6th of September, they finally emerged. These are Parasteatoda tepidariorum — note the leopard pattern on the abdomen. That’ll turn into a more complex mottling as they get older. Also see how the legs are mostly pale, but with distinct bands.

Steatoda triangulosa has a longer incubation time of 30 days, and the spiderlings emerge with pale abdomens and black, hairy legs.

The important thing about this is that we can nail down how long the incubation period for both species is under our specific culturing conditions. Now we wait for the Steatoda borealis egg sac to hatch out so we know its incubation period. Then…comparative embryology!

By the way, the lab was hectic this morning, with 150 tiny baby spiders, each about 3/4 of a millimeter long, emerging all at once and immediately trying to disperse. There was a cloud of barely visible dots all radiating out instantly from the locus of their home vial, while I was frantically trying to gather up individuals and put them in separate containers. Some, I’m sure, escaped.

Hmmm, is it ever a good thing when a scientist says that?

Since I avoid posting spiders here, you’ll have to go to Patreon or Instagram to see the baby picture.