A strange form of crypsis in butterflies

“Crypsis,” as you should all know by now, is just a fancy scientific word for “camouflage.”  Often cryptic animals will hide from predators by mimicking their background, but here’s a case in which one part of an animal mimics the other.  Have a look first and see if you can figure out what’s going on.

(The photo, tweeted by Bug Girl, and posted on flickr by itchydogimages, John Horstman, is identified as a Long-Banded Silverline, Spindasis lohita, Lycaenidae. It was taken on February 23, 2013 in Simao, Yunnan, CN, using a Sony DSC-R1.)

Picture 1

This is a case of a “false head” in a butterfly. While the real head is inconspicuous, the posterior part of the wings bear a gaudy, attention-attracting false head, colored orange and replete with fake eyespots, fake antennae, and fake legs. Note as well that the wing patterns call attention to the fake head by converging on it.

One evolutionary explanation immediately comes to mind. Predators—and by this I mean birds—are operating on the old Chinese proverb, “To kill a dragon, first cut off its head.”  Birds have either learned (or perhaps have an evolved propensity) to strike at insects by pecking at their anterior (front) section, which is far more likely to debilitate it than a peck at the rear, on the wings.  By evolving a “false head”, an insect has a higher chance of surviving a bird strike since the bird pecks at the false head, allowing the butterfly to escape with minimal damage. In fact, I remember reading about studies in which on finds “false head” butterflies with the fake head are bitten far more often on the wings than str “regular” butterflies. Doug Taron at the Peggy Notebeart Nature Museum here in Chicago verifies this (and shows more false-headed butterflies):

In 1980, scientists from the Smithsonian attempted to demonstrate that predators could be fooled into attacking the wrong end of the butterfly. They collected hundreds of butterflies in Panama and Columbia, and divided them into groups based on the number of head-like features were present in their wing patterns. Consistent with the false head hypothesis, the greater the number of head-like features, the more likely wing damage due to predator attacks was to be directed to that part of the wings.

I also remember—though I can’t provide chapter and verse—that birds also automatically strike in front of what they perceive as the head, like a sniper leading a target with his rifle. This anticipates that the butterfly will take off when attacked, and that a strike directed right in front of the head will intercept it in mid-flight.  This makes it even more likely that false-headed butterflies will escape predation, since the bird will be aiming behind the entire insect.

Finally, I recall that some of these butterflies actually land and then turn around 180º after landing, just in case a bird is watching them land. That will confuse the bird even more about which end is the head. I’ve found one paper in the 1982 volume of Journal of the Lepidopterist’s Society by Torben B. Larsen that substantiates this behavior in a Nigerian butterfly.

There are several species of butterfly with such patterns, which obviously are examples of convergent evolution. Here are two more:

From Urban Wildlife Guide, the gray hairstreak butterfly, Strymon melinus:

smallerimage

This butterfly is striking enough that its non-scientific name is the “Common false head” (photo from TrekNature by MIKE WNR [drmw]); this is the butterfly documented to do a 180-degree turn after landing:

oxylides_faunus

Oxylides faunus

20 Comments

  1. Diana MacPherson
    Posted May 19, 2013 at 6:37 am | Permalink

    Very interesting stuff about the butterflies. And now a brief ancient greek lesson – crypsis comes from κρυπτος (kyryptos) which means hidden or secret.

  2. Posted May 19, 2013 at 6:54 am | Permalink

    These are wonderful butterflies. Some of them do something even more amazing to enhance the illusion—they gently rub their hind wings together, making the fake “antennae” (which are not straight in these species but curved so that they cross their counterpart on the opposite wing) scrape against each other so they slowly gyrate like real antennae!

  3. marksolock
    Posted May 19, 2013 at 7:06 am | Permalink

    Reblogged this on Mark Solock Blog.

  4. Posted May 19, 2013 at 8:06 am | Permalink

    Lovely stripy Tim Burton stockings on the faunus!

  5. John J. Fitzgerald
    Posted May 19, 2013 at 8:11 am | Permalink

    Interesting discussion of honey comb construction.

    See: http://www.npr.org/blogs/krulwich/2013/05/13/183704091/what-is-it-about-bees-and-hexagons?ft=3&f=111787346&sc=nl&cc=es-20130519

  6. Mark Joseph
    Posted May 19, 2013 at 8:14 am | Permalink

    And the creationist explanation for this type of crypsis is…?

    (Rolls on floor, laughs ass off, has to go sit quietly for a while to catch breath)

    OK, breathing normally again. Serious point. The creationists harp endlessly on a few favorites (which, of course, they don’t understand), never offering any explanation other than “godidit” while ignoring a huge number of cases where natural selection (such as these butterflies) and sexual selection (peacock tails) form a parsimonious, rational, and testable explanation.

    The situation is exactly analogous to the difference between an engineer who explains an internal combustion engine in terms of mechanical parts and the laws of physics in burning fuel, and someone who says “magic invisible fairies make it happen by magic, just like they do with refrigerators, iPhones, and color printers.”

  7. Mark Joseph
    Posted May 19, 2013 at 8:22 am | Permalink

    Bird: “You stupid butterfly; you don’t even know your head from your butt.”

    Butterfly: “And neither do you!”

  8. KP
    Posted May 19, 2013 at 8:58 am | Permalink

    It works this way in fish too. Many species have false “eye spots” (ocelli) toward the caudal end. Predator lunges for the tail, prospective prey fish swims forward and avoids becoming dinner.

  9. woody benson
    Posted May 19, 2013 at 10:32 am | Permalink

    Jerry / Lou,
    Note in the last photo that the red line on the hind-wing of Oxylides faunus, the about-facing butterfly of Larsen, produces a mirror image of the outline of the hindwing! Not only has the butterfly switched its head for its tail, it has reversed its wings to match!

    • Posted May 19, 2013 at 10:41 am | Permalink

      Astute observation! Very cool; I didn’t notice that at all.

    • Posted May 19, 2013 at 3:43 pm | Permalink

      Yes, very neat! I also hadn’t noticed that.

  10. Marcoli
    Posted May 19, 2013 at 11:09 am | Permalink

    There are also caterpillars that do a similar trick where they make you guess which end is the head. The monarch caterpillar being a familiar example:
    Monarch Caterpillar

    • woody benson
      Posted May 19, 2013 at 11:25 am | Permalink

      Caterpillars spit.

    • Mark Joseph
      Posted May 19, 2013 at 12:31 pm | Permalink

      Obvious question from someone (me) who doesn’t know as much biology as he should: Do false-headed caterpillars give rise to false-headed butterflies? And, do all, some, or no false-headed butterflies come from false-headed caterpillars?

      • Marcoli
        Posted May 19, 2013 at 2:29 pm | Permalink

        The false headed caterpillars I know best are in the monarch family, and none of those exhibit false heads as adults. So not as far as I know.
        On the other hand, the swallowtail butterflies are thought to be another family that uses the false head strategy. The tails on the hind wings being ‘antennae’, generally with some bright spots nearby on the wings which pass for eyes. This false head strategy does not seem as well done as the butterflies shown above, but birds often peck at their hind wings of swallowtails so it appears to work. In many species of swallowtails the caterpillars mimic snake heads. The can even inflate a thing that looks like a forked tongue that is hidden away just behind their real head. You can Google for swallowtail caterpillar and you will see what I mean. Of course the whole strategy here is to not make a bird think the rear is the head, but rather to deceive the bird into thinking they have come across a snake in the bush.

  11. Marella
    Posted May 19, 2013 at 7:56 pm | Permalink

    Fascinating, I didn’t know butterflies did this!

  12. Dominic
    Posted May 20, 2013 at 2:11 am | Permalink

    I suppose that it is a one-shot strategy though. If the fake head is damaged or lost to a bird, surely the wings would also be damaged? Are these short-lived species in adult form? In fact, what is the life expectancy of a butterfly as an adult?

    • Jonathan Wallace
      Posted May 20, 2013 at 3:50 am | Permalink

      Life expectancy varies substantially with some species lasting only a few days after emrgence and others several weeks or more. Some species emerge as adults in one year, hibernate and mate and lay eggs the following Spring.
      It is not uncommon to see butterflies with a peck taken out of the wing and they seem to manage with surprisingly heavily damaged wings so the strategy would certainly seem to allow an individual to survive to breed after a bird attack.

  13. Posted May 20, 2013 at 3:47 am | Permalink

    As an evolusionist I find this absolutely fascinating, but as a layman (not a scientist) I am at a loss to understand how the species can develop this camouflage purely by means of mutation and adaptation.

    I have yet to come across a good scientific explanation of what mechanisms are used in this ability to “create” such bodily adaptations – and also the many imitations (mimicry) we see in nature.

    Maybe I have just not yet read the right studies – if so, please point me to them.

    Due to my lack of knowledge I can only assume that there is some kind of “creative” consciousness in the species. No, not that of an outside “creator”, but some kind of ability in the genes to plan and then produce such camouflage. But that notion opens up a huge question on how such abilities developed – and why only in certain species – apparently?


2 Trackbacks/Pingbacks

  1. […] A strange form of crypsis in butterflies (whyevolutionistrue.wordpress.com) […]

  2. […] member of the Lycaenidae family, and it defends it self against birds, not spiders . Nice bit of mimicry there: by pretending to be itself, but in reverse, it makes sure it gets bitten in the rear end, […]

%d bloggers like this: