Caterpillar mimics scorpion or ant

Matthew emitted this tw**t showing what looks to be a remarkable case of mimicry: a caterpillar (Lepidopteran larva) mimicking a scorpion, and ant, or both. Scorpions are of course not insects but arachnids (like spiders) and have eight legs. Nevertheless, the mimicry is remarkable, and it’s hard to believe that this is anything but a genuine mimic.

I’ve enlarged the mimic so you can see how amazing it is, complete with a fake stinger:

Here’s the moth of Stauropus fagi, which rests with a large part of the hindwings protruding:

Now Matthew may be wrong here, and the model for this mimic could be a stinging ant, as the head looks remarkably antlike, and the scorpion “stinger” could be an exaggerated ant stinger. But it could be both, in which case we’d have an almost unique case of an insect mimicking two distinct arthopods (I know of no other). One way to tell is whether scorpions and ants are both found within the range of this caterpillar.

Wikipedia says this:

In the first instar the caterpillar feeds entirely on its own egg-shell and is unusual in that it mimics an ant or small spider. This is due to the long thoracic legs “and caudal appendages which are ever nervously twisting about”. If the larva is disturbed during this period it wriggles about violently in the same manner as an injured ant.

 

15 Comments

  1. busterggi
    Posted December 27, 2017 at 1:14 pm | Permalink

    The invertebrates really do this up so much better than us boney critters.

    • Paul S
      Posted December 27, 2017 at 2:25 pm | Permalink

      Too true. I can only mimic my dad, and not that well.

    • Posted December 27, 2017 at 6:43 pm | Permalink

      This is actually an observation with an important evolutionary lesson. The ability of natural selection to produce such near-perfection of mimicry or camouflage is limited by the effective population size of the organism. When effective population size is low, genetic drift is large and this puts a lower limit on the effectiveness of natural selection. The “nearly neutral theory” of population genetics actually leads to a nice simple equation expressing this relationship.

      Vertebrates generally have much lower effective population sizes than invertebrates, so natural selection simply cannot produce such perfection in vertebrates.

      • Diane G.
        Posted December 28, 2017 at 1:03 am | Permalink

        Makes perfect sense when you think about it. Thanks Lou!

  2. Posted December 27, 2017 at 1:23 pm | Permalink

    Wow! That IS astonishing mimicry!!

  3. Liz
    Posted December 27, 2017 at 1:32 pm | Permalink

    Fascinating.

  4. Posted December 27, 2017 at 1:41 pm | Permalink

    I just saw this caterpillar today on Flickr, so this is quite a coincidence. I don’t quite ‘get’ the mimicry, but perhaps like many other cases you need to see how it moves to get the full effect.

  5. Posted December 27, 2017 at 1:45 pm | Permalink

    It does move rather creepily. As shown here: https://www.youtube.com/watch?v=V1wV9P-f7Dc
    And here:

    • Liz
      Posted December 27, 2017 at 2:18 pm | Permalink

      Interesting to see them provoking it. I wonder if the “stingers” actually do anything and why there are two of them when both the scorpion and stinging ant only have one as far as I know.

      • Mark Sturtevant
        Posted December 27, 2017 at 2:51 pm | Permalink

        I am not sure what are the paired appendages that are considered to be the ‘stinger’. But if they are the last pair of caterpillar prolegs, it could be that it could not get the mutations to merge them into a single appendage since doing that would be really hard.
        As we learn quite often about mimicry, the display does not have to be really good to derive some benefit.

    • Diane G.
      Posted December 27, 2017 at 4:12 pm | Permalink

      Cool vids, thanks!

  6. lkr
    Posted December 27, 2017 at 2:14 pm | Permalink

    I think the head is fairly standard-issue lep larva. Leg movement is hardly cryptic, seems as much ant-like as any arthropod coming to mind. And abdomen would look a little scorpionish if it weren’t for the paired ‘horns’ [possibly scent glands?] where the stinger would be. If it weren’t for the ostentatious movement of the legs, it could just as well look like a poor attempt at phasmid-style miming of dead leaves.

    A lot of mimics and cryptics scream out their models. This would take a good bit of familiarity with the caterpillar’s habitat and the local arthro-fauna to make even an educated guess.

    But certainly a lovely creature from a Designer who used his good stuff on those NOT made in His image, yes?

  7. Posted December 27, 2017 at 6:08 pm | Permalink

    Makes me wonder if being creepy enough would be sufficient to deter predators.

    • loren russell
      Posted December 27, 2017 at 6:12 pm | Permalink

      Bluffing can work — viz all the videos we see of tiny cats running off bears and other large animals.

      If this were a scorpion mimic, I’d predict stabbing movements if touched.

  8. Posted December 28, 2017 at 1:31 am | Permalink

    Great post. How clever.


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