A remarkable pupa that resembles a snake—and moves!

January 20, 2021 • 1:30 pm

Over five years ago I wrote about a remarkable adaptation in insects: mimicry of snakes. Remember that “holometabolous” insects go through very different life stages, and this includes Lepidoptera, which have larvae that become pupae (also known as “chrysalises”), and out of those pupae hatch the winged adults. The larvae (“caterpillars”) are often highly edible to birds and other predators, and have to evolve various strategies to avoid being eaten. Snake mimicry is one such strategy.

In 2020 I described one example of a caterpillar mimicking a snake. When the caterpillar is disturbed, it displays a remarkably snakelike underside and rears its head like a venomous snake. This is the Snake-mimic caterpillar, Hemeroplanes triptolemus, a moth from the Amazon rainforest found in Puyo, Ecuador. The video was taken by the late Andreas Kay, who rediscovered my frog Atelopus coynei. (Kay’s photos are now curated by reader Lou Jost.) I’ve put Kay’s video below again—it’s the second one in this post.

But pupae, being immobile (well, as you’ll see, they can sometimes move a little), have a bigger problem, for they don’t have much behavior to deter predators. In another post from 2015 I described and showed some photos of a pupa that, like the caterpillar above, also resembles a snake. (It’s a different species from the one above; the pupal mimic becomes a butterfly while the larval mimic turns into a moth.) I also noted that the pupa could actually move a bit, and it’s likely that even a little motion might deter a predator. But at that time I had no video to show.

Recently I found that in fact Kay did take some video of the snake-mimic pupa and had put it up in 2018. Ergo, just below, in the top video, you can see a pupa that resembles a snake. The resemblance of both moth and butterfly mimics is so close to that of a snake, both morphologically and behaviorally, that it’s hard to think of any explanation other than Batesian mimicry.

First, here are Andreas’s YouTube notes:

This chrysalis or pupa of the Daring Owl-Butterfly, Dynastor darius, was filmed in the Jardin Eco-botanico Mindo, Ecuador. It mimics the head of a snake which gives it an advantage in the struggle for survival by scaring off predators such as birds. It has fake eyes, a fake mouth, fake scales and even strikes like a snake if disturbed, as shown in this video.

And look at it move! How does the immobile and developing butterfly adult know that something’s threatening it? It appears to have a sense of touch.

And here again is the moth larva mimicking a snake; a video I showed before.  You might want to ponder the incipient stages of this adaptation—what were the first snake-resembling features to evolve?

16 thoughts on “A remarkable pupa that resembles a snake—and moves!

  1. Lovely!

    If the caterpillar has the movement, as a reflex whenever it is threatened, does that give the initial pupa stage the same muscles that are stimulated by …whatever? Also how long does the reflex last? How long is it a pupa?

    1. Butterfly and moth pupae in general can wiggle, but I’ve always see them wiggle from side to side when disturbed, or the wiggle in a circular fashion. So movements per se are primitive in that sense. But what seems novel here is that this pupae seems inclined to just wiggle up and down, which makes it a more convincing snake.
      I’ve felt there is a period ~ mid-way thru the pupal stage where a pupa may not be able to wiggle. This could mark the time when the larval muscles had broken down, but the adult muscles are not yet built up enough. So before and after they can wiggle, first b/c of larval muscles, and later b/c of adult muscles. Now I could be astray on this impression.

  2. This is way cool! A chrysalis typically is camouflaged to blend in with its surroundings. So species that hang up on trees would likely resemble tree bark like this one does (a bit).
    Snakes are commonly camouflaged in a similar fashion – even venomous ones.
    So it seems one small step to take for a species that is already camouflaged to evolve to mimic a snake that is camouflaged. But why bother? WTF, evolution?

    1. The pupae pictured here looks very much like the head of a boa constrictor, a common South American snake that no bird would want to tangle with. (PS: boas are non venomous.)

  3. I remember your first post on this mimicry last year. Amazing then and this one is amazing now. This new pupa looks more venomous to me, as it has the looks/colors of a viper.

    And to ponder the incipient stages of the adaptation, I would imagine the eyes were the first features to evolve.

  4. It’s probably just a matter of time before the folks over at the Discovery Institute will proclaim this as Intelligent Design! 🙂

  5. What? You are the one claiming that evolution is true. Are you not going to explain how this happens? How does the insect know that the snake is the bird’s predator? And then consistently evolve to mimick a completely different creature to itself? Don’t leave it hanging!

    1. We don’t know how it happened for sure, of course–the order of the changes. Some pupae already move, but not to deter predation. Perhaps this one did. Any mutation that affected the color or pattern of a snake would deter predators who had learned to avoid snakes. The insect doesn’t have to “know” that the snake is the bird’s predator; mutations conferring resemblance to a snake would leave more offspring than pupae lacking the mutation. We don’t know the order in which the different mutations arose. Perhaps one for color was first, or rudimentary eyespots, or whatever.

      But you don’t seem to understand how mimicry works: there is no “knowledge” that the pupae has to have. I recommend you read one of Dawkins books, like “Climbing Mount Improbable”, which deals with issues like this.

      I have given a brief explanation in case you’re not a creationist, but I am wary given that “you are the one claiming that evolution is true.” In fact, all rational biologists accept that evolution is true, not just me.

      1. As well as incorrectly supposing that the insect should “know” that the snake is a bird’s predator, the question also falls into the fallacy of thinking that there is intent involved in the process of evolution. Species do not set out with the intention of looking more like a snake or developing wings (or gaining any other adaptive attribute) any more than a sand dune ‘decides’ to align itself in a particular direction in relation to prevailing winds.

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