My hip hop band name will be “RTA Clade”

Now my brain is stuck on spider evolution, which is an awesomely cool subject, and how annoyed I am that creationists can spit on it with such ignorant contempt. So I have to mention another good article on the subject, Reconstructing web evolution and spider diversification in the molecular era. There are so many papers on this topic, and there’s a guy affiliated with the Discovery Institute writing a whole book on the subject while unforgivably ignorant of it all. So here, cogitate on this:

Optimization of web architecture on the preferred topology. Black stars indicate strong support for a node from both MP (jackknife > 75%) and Bayesian (posterior probabilities > 90%) analyses, and gray stars indicate nodes strongly supported only by one methodology or with jackknife 50–74%. Branch colors represent MP reconstruction of webs, and pie charts represent the relative probabilities from ML reconstructions. Colors of boxes to the left of taxon names represent their webs, and open boxes indicate that taxa do not spin prey capture webs.

There’s also information on the topic of orb web monophyly that I mentioned in the previous post.

The monophyletic origin of orb webs is strongly supported, despite conspicuous differences in the silk used to spin different types of orbs. This has important implications for understanding both web evolution and spider diversification. Instead of cribellate and ecribellate orb webs evolving in parallel, orb monophyly explicitly implies that dry cribellate capture spirals were replaced by ecribellate gluey spirals. This involves 2 major changes. First, a shift in the silk used to produce the core fibers of capture threads, resulting in novel tensile properties. The core fibers of modern (ecribellate) orb weavers are composed of flagelliform silk, which is much more elastic than the pseudoflagelliform silk core fibers of cribellate spiders. Mechanically, flagelliform silk functions like rubber, relying on entropy to resist motion of silk molecules and absorb kinetic energy during prey capture, allowing the capture spiral to expand and contract repeatedly. In contrast, cribellate silk relies on permanent rupturing of molecular bonds to absorb kinetic energy and deforms irreversibly during prey capture. The second major shift involves the mechanism of adhesion, from dry cribellate fibrils that adhere through van der Waals forces and hygroscopic interactions to chemically adhesive viscid glue in ecribellate spiders. This results in webs with greater adhesion per surface area and may have facilitated the transition from horizontal to vertical web orientation in modern orb spiders, which is associated with increased prey interception rates.

That paper also discusses something I didn’t mention. Did you know that about half of all spider species don’t make prey capture webs at all? They’re active hunters, like wolf spiders and jumping spiders, and they belong to an extremely successful monophyletic group called the RTA clade, short for retrolateral tibial apophysis, the best band name ever.

I think I need to go spend some time in the lab with my spiders to cool my brain down, before participating in the podcast this afternoon, which will not be about spiders.


  1. birgerjohansson says

    Moar good news as you relax: South African sources see preliminary signs the omricon variant may cause milder disease.
    My mind drifts to a possible solution of “how do we kill the fascists without killing non-fascists”: encourage the anti-vaxxer Qanon eejits.

  2. John Harshman says

    I’m afraid that the best band name ever would be Higgs Boson and the Large Hadron Colliders. I picture them as alt-country metal.

  3. birgerjohansson says

    How the hell has the winter weather enough energy to generate a fucking tornado?
    Don’t you need immense heat and thunderstorms for that?
    It is as if the Matrix just glitched.

  4. birgerjohansson says

    I get it. The MAGA Republicans are descended from the RTA clade, and the corporate Democrats are just sitting in their dusty webs while the world gets eaten around them.

  5. azpaul3 says

    Ok, I’m not a spider fan but this stuff is very interesting especially at the detail you are showing.

    Thank you, Dr. M.

  6. birgerjohansson says

    Now that you have time to relax, here is more good news. Sildenafil seems correlated to a 69% reduction of the risk of getting Alzheimers.

  7. John Morales says


    Sildenafil seems correlated to [blah]

    It seems, does it? To two figures of accuracy, even!

    Re “hip hop” bands, that’s something for the pure finders. Just less useful.

  8. stroppy says

    birgerjohansson @6

    Tornado newsiness from NBC

    …This event was caused by a volatile atmospheric set up that was primed to produce violent and long-track tornadoes. Friday featured unseasonably warm and record-setting temperatures that felt more like Spring than mid-December. This warmth, combined with high humidity, provided ample fuel for the storms.

    As the day progressed, the wind fields strengthened helping to create the dynamics, or “spin,” in the atmosphere needed to produce tornadoes.

    A cold front charging through the region provided the trigger for the storms, which with all the ingredients in place created ripe conditions for a tornado outbreak.

    Compounding the favorable atmospheric ingredients is the fact that the United States is currently in a La Niña pattern, which historically increases tornado frequency across the Mississippi Valley.

    And climate change may also have played a role.

    Research reveals that climate change may be causing tornado alley to shift East, out of traditional tornado alley of the Great Plains and into parts of the Mississippi Valley.

    While meteorologists and climate scientists cannot yet say that tornado frequency is increasing globally due to climate change, it can be said with relative certainty that tornado frequency and associated vulnerability is increasing for the Mississippi Valley and Midwestern regions of the United States….

  9. wzrd1 says

    Well, OT, but I’ve learned of a new Gen Z thing. Birds aren’t real, a tongue in cheek poke in the eye against all of the other conspiracy theory drivel out there.

    BTW, they omitted webless spiders, I guess that they just don’t count?

  10. davidc1 says

    @2 Well over here in GB ,some people are saying it will cause 75,000 deaths over the winter.

  11. birgerjohansson says

    John Morales @ 12
    Yes, since the correlation was found by data mining more strict experiments obviously needs to be done. That is why I wrote “seems”.
    But since Alzheimers is such a bloody awful disease that has withstood so many experimental drugs, I thought this news was worth passing on.
    The idiot governor of Florida has set aside 1 billion $ for flood control infrastructure, but still denies climate change is a problem .

  12. DanDare says

    Thanks for the science PZ.
    I have a dreadful phobia of spiders. Over the years I made a promise not to kill them out of hand but, where I can, capture them and relocate. In Australia that is a bit daunting.
    Your articles give me good reason to look at actual spiders and see their anatomy. This helps reduce and contain my phobic reaction. That’s very pleasing.

  13. brightmoon says

    I tend to freak when I see spiders but there’s a large daddy long legs spider in my bathroom that I refrained from killing and will watch . (Yes I can tell the difference between a daddy long legs and a daddy long legs spider )

  14. dorght says

    Is there a distinction made between webs used to catch prey and a web mass used as shelter?
    I couldn’t find the brown recluse (Sicariidae) on any of the diagrams. I got bit by one when I rolled onto it in bed. It died, I had a huge burning hive like reaction down my back. I told the Dr. that I had vacuumed up its web from behind the nightstand by my bed earlier that day. He stated flatly that the brown recluse doesn’t make a web. In hindsight I think we may have both been wrong or at least made incomplete statements.
    I took its corpse in with me to the doctor for positive id (3 sets of duplex eyes). And made peace with the numerous other brown recluse in the turn of the previous century house because I really enjoyed not having other bugs (especially silverfish) in there.