Orchid mantis: does it really mimic an orchid?

March 9, 2015 • 9:45 am

I believe I’ve posted several times about the “orchid mantis,” a term for a variety of mantises that mimic—or appear to mimic—orchids. These mantids are believed to sit among flowers, and resemble the flower so strongly that pollinators like bees try to pollinate them. But instead of getting pollen, the bee gets snapped up by the mantid when they fly into its arms. Here are a few of the mantids showing their resemblance to flowers:

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Below is an Attenborough video showing the mantis deceiving a bush cricket, who loses its life. It also shows another cool fact: this species is not mimetic as a juvenile, but aposematic: it has “warning coloration” showing that it’s toxic. For some reason, perhaps connected with the mantis’s increasing size, it changes shape and color as it ages, changing from conspicuous to cryptic.

This is a classic example of “aggressive mimicry,” so called because the purported evolutionary pressure was to get food (through aggression) rather than simply to hide form predators. But, like many cases of mimicry, the “pollinator-deceiving” mimicry is inferred, and hasn’t been scientifically tested. To do that you’d have to experiment on these species (and they’re not easy to come by), showing that pollinators do indeed mistake the mantis for an orchid flower. And to test another hypothesis—that the mantis gains additional camouflage by hiding among the orchids it’s said to resemble—you’d have to show that the mantis gets more prey when it’s sitting among flowers than when sitting alone. That hadn’t been done either.

Further, there’s an alternative hypothesis: that the mantid isn’t camouflaged to deceive prey, but to deceive predators. After all, the aposematic coloration of the juvenile above probably evolved to warn away predators who have learned to avoid the toxicity associated with that coloration. And that implies that something tries to eat these creatures. Finally, the flower-resemblance of the adult could serve to simultaneously deceive both predators and prey.

To test these hypotheses, James O’Hanlon, Gregory Holwell, and Marie Herberstein, a group of researchers from Australia and New Zealand, did experimental tests on insects and flowers in Malaysia. The results appear in the two papers at bottom (with links). What they found is that the conventional wisdom is correct in some respects, but the story is more complicated.  I’ll just summarize the main findings. Tests were done on a single species of tropical flower mantid: Hymenopus coronatus.  Here’s a photo of a subadult female from the American Naturalist paper:

Screen Shot 2015-03-09 at 8.53.15 AMHere are the salient results:

  • Yes, the mantids do mimic flowers, but not necessarily a particular orchid. This conclusion comes from color-spectrum analysis of the insects and flowers filtered through what a pollinator (a bee) really sees. This shows that the mantid resembles the colors of a number of local flowers, but the authors weren’t able to find a specific orchid that the tested mantis resembled. (Note: they didn’t look all that hard.) But given their ability to find mantids sitting around on many flowers besides orchids, and even on vegetation, it’s likely that the mantis evolved to resemble a generalized flower rather than a given species of orchid. This makes more sense because a given species of orchid is not ubiquitous in the rain forests, and they flower irregularly.
  • Tests in which the researchers observed pollinators “inspecting” (deviating from a flight path to come closer to an object) a control object (a stick), a common species of flower in the area tied to a stick, and a mantid tethered to a stick showed that pollinators barely visited the stick, visited the flower moderately often, but visited the mantid most often (in fact, several instances of predation were observed).  This shows that the mantid by iteself is even more attractive than the flower, so it’s not simply hiding itself among flowers  to enhance its resemblance to a flower.
  • However, mantis sitting next to flowers got a higher rate of pollinator inspection than did solitary mantises, and the higher the density of flowers around a mantis, the more the mantis was “inspected”—and presumably the more noms it got. Therefore, although mantids can attract pollinators on their own, this ability is enhanced when they’re sitting amongst a bunch of flowers. Because solitary mantises seem more attractive to pollinators than are solitary flowers (implying that the mantids don’t have to hide to deceive the insect), this result probably reflects the fact that a patch of flowers simply draws more insects than do solitary flowers.
  • The authors tested, using a Y-tube, whether the mantids chose to go to flowers more often than to leaves, which would imply a form of habitat selection. They found no effect: mantids went down the “leaf” arm of the Y as often as down the “flower arm”.  So, though it may be adaptive for a mantid to be drawn to a group of flowers (because it gets more prey), that behavior hasn’t evolved. But a Y-tube test may not be the best way to test habitat selection, as it’s an extremely artificial situation.

So the conventional wisdom confirmed here is that the mantids do resemble flowers, fool predators that way, and can get noms by their resemblance. The conventional wisdom that was overturned is that these mantids resemble orchids, or a specific species of orchid. Also, the results don’t support the notion that the mimicry is imperfect, so that the mantids must hide among flowers to get any prey. They do get more prey when hiding among flowers, but that’s because more pollinators are attracted to large groups of flowers. Finally, the authors found no support for the idea that mantids seek out the flowers and hide among them. Because that behavior would seem adaptive, I’d like to see better tests, tests using, say, a large cage with flowers and leaves instead of a simple Y-tube choice experiment.

But, of course, lots of work remains. Did the authors miss an orchid that the mantis really resembles? Does the mimicry protect the insect from predation in addition to helping it find prey? Are there other cues that attract insects besides the color and shape of the mantis? It is possible, after all, that the insect has evolved pheromones, or a scent, that also attracts pollinators. Remember that the case of orchids that mimic insects to get pollinated (the reverse situation; deceived bees try to copulate with bee-mimicking orchids and, in the process, get pollen stuck to their bodies), those orchids have evolved a scent that mimics bee pheromones.

Finally, the photos above show that far more than color is involved in this mimicry. The mantids have developed elaborate petal-like extensions to their legs and bodies, as well as special markings, that also mimic flowers. The authors tested only color resemblance, but clearly the mantid also mimics the shape of flowers. It’s likely that a pollinator will be attracted to the general vicinity of the mantid by its color (bees don’t see that well!), and then make a final decision to approach more closely based on shape. That would impose strong selection on the mantids to look more like flowers.

h/t:Matthew Cobb

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References:

O’Hanlon, J. C.M.E. Herbersteinand G.I. Holwell. 2014. Habitat selection in a deceptive predator: maximizing resource availability and signal efficacy. Behavioral Ecology, online, doi: 10.1093/beheco/aru179.

O’Hanlon, J. C., Gregory I. Holwell, and Marie E. Herberstein. Pollinator Deception in the Orchid MantisThe American Naturalist, Vol. 183, No. 1 (January 2014), pp. 126-132

36 thoughts on “Orchid mantis: does it really mimic an orchid?

    1. Ditto. Just confirming that we do read these posts.

      Also the previous nudibranches post (cue Beavis and Butthead style sniggering).

    2. Same here. Read it. Enjoyed it. Found it very interesting. Nothing intelligent to say. 🙂

  1. Fascinating stuff. The alternative hypothesis you mention i.e. that the mimicry evolved as a defence against predators, is not ruled out by these results though, is it?

    There are probably many examples of traits that serve both to help an animal catch its own prey and to evade being caught itself by other predators. Flight would be such an example; a bat or a bird can more readily flee predators whilst being able to exploit a whole smorgasbord of aerial prey that would be unavailable to a non flying predator.

    1. I agree. And we should consider how a mimic really resembles their prey. Flowers often advertise their state to insect pollinators by ultraviolet markings. I wonder if the mantis might use these markings as well.

    2. As I said, both types of selection could have operated to create this mimicry. The first thing to find out for the predator-protection theory is whether anything actually eats adult mantids. I suspect that’s true.

  2. The idea that the mantis may also use other means to attract prey in addition to visual mimicry is interesting. Presumably using caged, hidden mantis it would be possible to test for the use of scent mimicry.

  3. Nice review. There have been many posts on mimicry. Could Professor Ceiling Cat be planning a book on the evolution of mimicry? The subject is replete with what used to be called natural history.

  4. Boy are mantids cool, and I’m tempted to say they’re totally awesome.

    Also totally awesome is this particular post, which answered each question I had with the next sentence.

    Does it not boggle the mind that this kind of adaptation so truly blind? Millions of years of slight bee preference to inspecting mantids that are little more flower-like than the others honed an animal’s appearance into complete flower-like-ness. This is, literally, awesome!

    I guess generic flower-like-ness has to be the theory absent the identification of a specific orchid to resemble. Still, the markings are so not-generic: the tiger stripes, especially, seem so orchid-y it’s hard to imagine those would emerge without some kind of model for the prey to favor.

    How far afield might a researcher need to look in order to rule in or out a specific model flower? Presumably farther than the glade in which they are working. Could these kinds of markings have developed in another environment and simply remained (or be in the process of devolving away) after the animal moved to a more productive hunting ground? Or could there have once been a dominant flower in the area that has died out and, similar to the case of migration, the animal remains flower-like enough that the visual pattern remains effective post-orchid?

    1. One feature that I think is part of the story is that many mantids are already flower-ish or leaf-like in form b/c of earlier natural selection. It can be from those species that you can get a strong flower mimic.

  5. The way the abdomen mimics the lip of the orchid (see third picture in the first set of photos) is extremely convincing, if slightly generic. There are many orchids that have lips very similar to that.

  6. Jerry/Matthew- What a good information-packed post.

    If I may offer an opinion, one shouldn’t, I think, jump to the conclusion that a creature is aposematic (unpalatable) simply because it has gaudy colors. My casual Google search for the terms “aposematic mantid”, “unpalatable mantid”, “distasteful mantid”, and “toxic mantid” produced no valid hits outside of WEIT. I am also unaware of reports of chemically defended mantids. Because mantids tend to be generalist predators, it seems unlikely that much venom could be sequestered by most individual mantids even in species able to consume chemically protected prey. Although mantids can be feisty, their bodies are soft, and it seems unlikely, even if individuals should occasionally make or store unpalatable chemicals, that one would often survive being tasted by a predator (read bird). Distastefulness, if of small individual advantage, would be difficult to evolve by natural selection. Mantis nymphs do not seem to cluster much, and kin selection mediated by predator learning might also be weak. That said, I am speculating from my general impressions, and a mantid biologist may come along and say I am all wet.

    Another caveat: If bright colors are actually conspicuous depends on where the creature lives – its ecology — and the sensory equipment of the observer. A silver beetle may ‘become’ a dew drop and a bright orange bug ‘become’ a dingy bump on the red fungus it calls home. Alternatively, the creature may be so intrinsically conspicuous and difficult to snare – think of big red dragonflies and yellow butterflies – and color may be ‘ecologically’ irrelevant.
    Finally, the conspicuous red and black mantis we see, rather than aposematic, may be a mimic of some distasteful model yet unobserved. I have no idea what the nymph of the orchid mantis might mimic where it lives, although something similar to the ambush bug pictured in this link seems possible (http://bugguide.net/node/view/539397/bgimage).

    1. Perhaps there’s a sense where one can use “aposematic coloring” to refer to the color scheme only (i.e., making no implication as to whether the organism itself is mimic or model), rather than have to spell out “Batesian mimic of an aposematic organism” all the time.

      That would also deal with the case of not knowing which–mimic or model–you were looking at.

      I did think the context was clear, here, though.

      Come to think of it, I suppose there’s a third option for mantids, in addition to camouflage and defense, and that would be offense. I.e., the mimicking colors of the mantid could allow closer approaches to the model, giving the mantid a greater opportunity to prey on it. (But the mantid would then have to be unaffected by the model’s toxicity, of course…)

      1. Merriam-Webster defines aposematic as “being conspicuous and serving to warn”, as, for example, against a sting, venom, or bad taste. Being aposematic is not just having bright coloration. If it is conspicuous, just call it “conspicuous”. That way it is less likely to create “confusion”.
        I still would like to know if anyone is aware of a truly aposematic (chemically protected) mantid? There are some pretty nasty grasshoppers.

        1. Rereading the OP, I see that Jerry did not simply mention that the juvenile mantid had aposematic coloring, he stated that that means it is toxic. So without further knowledge, I guess I agree with you in wanting to know if that’s the case or not.

          It would seem more likely to me that it sports mimic aposematism rather than toxicity itself, but I have no basis to make such a claim without doing a lot of research.

          That could be what Jerry meant to say as well, but he has to dash these pieces off in a hurry, as you can imagine.

    2. The aposematic mantid seems colored like a scorpion, for example, and other predators might confuse the two, recognizing only the color combination as a warning signal. That is, I think, what Prof. Coyne was saying — an act of mimicry meant to do the opposite of its adult peer’s flowery mimicry.

  7. The “general flower” mimicry makes a lot of sense for the reasons stated: It needs to be flexible and generally useful (or at least it will thrive more if it is).

    1. Which is probably often true; but in some environments certain organisms are more successful with specialization.

  8. I play with a lot of bugs and can’t remember reading about this switch in defense from aposematism to mimicry. Are there other examples? And presumably the adult is still toxic. Wouldn’t this lend itself to mimicry? If the aposematism isn’t conserved through to the adult stage wouldn’t something confer greater success?

    1. Aren’t there lepidopterans, esp. moths, with aposematic larvae and cryptic adults? Of course, in that case the adult has an entirely different diet, if it eats at all.

    1. Yeah, that’s one more plus for science over woo! With the former, it’s one fantastic story after another, with new stories coming along all the time. With the latter, it’s just bloviating over the same old, hackneyed, often ludicrous stories over and over and over. 😀

  9. If these insects mimic a particular species of orchid, then this is unlikely to be a rare species. Otherwise the selection pressure can hardly have been strong enough.

    So we are looking for a relatively common orchid species that occurs in Malaysia and beyond.

    One that I can think of is Eulophia spectabilis. See for example: http://idao.plantnet-project.org/orchisasia/genre/Eulophia/Eulophia%20spectabilis/

    However, there are many other, far less common orchid species that superficially resemble this one in colour pattern. See for example Dendrobium ceraula from the Philippines: http://www.orchidboard.com/community/attachments/dendrobium-alliance/59273d1315310760-dendrobium-ceraula-white-color-form-img_3498.jpg

    This resemblance is due to independent, convergent evolution; it is not the case that one orchid imitates another, because they occur in different habitats. My guess is that the mantis similarly resembles orchids because of independent, convergent evolution rather than through mimicry.

    1. It is unlikely that the mantis resembles an orchid because of convergent evolution. The form of the flower and the body form of the mantis are ‘solving’ very different problems. The similarity of the mantis to an orchid is either coincidence (and the resemblance is so good that seems highly unlikely) or it is mimicry. It may well not be mimicing a specific orchid species but rather a generic orchid but i would think it is certainly a mimic.
      The similarity between the different orchids that you mention may well be due to convergent evolution of course, although shared phylogeny would be sufficient explanation for reasonably closely related species.

      1. The similarity between those orchids is definitely due to convergent evolution, because they are not closely related.

        You say that the mantis and the orchid have to solve different problems. But that is not true. They both are a solution to the same problem: how to attract insects. They just happened to converge on a similar solution, which is why it’s called convergent evolution.

  10. Wonderful animals. Now that spring is in the air, I can hardly wait to get out there in the woods and fields. I saw a Robin and Blue bird the other day. With 4 feet of snow on the ground it will be a while yet before mantises and butterflies and bees are out.

  11. Forgive me for not reading all the comments, first, to see if this is redundant:

    Would the cricket have eaten away at the orchids, blossom and/or plant? If so, maybe the mantid protects the orchid by eating orchid predators while hiding in the orchid from mantid predators — a symbiosic relationship.

    Might the dangerously attractive younger mantid act as bait to draw crickets and others toward the adult mantids? If the filming had continued, might it have shown the adult mantid sharing its prey with the younger?

    Reading that pollintators chose the flower-impersonating mantid over the real flower, I thought “pheromones”, too.

    And, in that case, the mantid + flower combination yields more pollinators coming to flower and mantid, for potentially heightened pollination and more mantis munchables.

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