Tuesday, September 3, 2013

Hiding behind your Worst Enemy

Many species that are pursued by predators pretend to be what they are not to protect themselves. They may mimic toxic, dangerous or noxious tasting models or they may just become invisible sporting cryptic patterns that blend into the background.

Eye spots of moths and butterflies that are revealed with a sudden flick of the wings are widely accepted as a signal to scare or confuse predators. If you have ever seen the up-side down stance of an Eyed Silkmoth that feels threatened you can easily imagine that a hungry bird might be scared away from this fat clumsy morsel that suddenly resembles a cat or an owl. And maybe the scare even works as a defense against the attack of a lizard?

Antheraea oculea (Western Polyphemus Moth)
Most reptiles are predators of insects - the diet of many lizards consists entirely of arthropods and even baby alligators often grow on the proteins of grasshoppers and moths until they are big enough to hunt other prey.

But this isn't where the relationship ends. Evolution has linked insects and reptiles through more than just the food chain.

Papilio rutulus (Western Tiger Swallowtail) caterpillar

Observe the spots on the bloated body of the Western Swallowtail caterpillar: to my eye they not only distract from the real head that remains tucked down and hidden, they also seems to suggest the face of a snake.

Elephant Hawkmoth, Deilephila elpenor by Amy MacDonald
The resemblance to a snake seems even more impressive in the caterpillar of the Elephant Hawkmoth because it is longer, bigger and adds a cobra-like threatening posture to the mere looks of a serpent.
When my friend Alex Pelzer was working on his Ph.D. using these moths as his model, we tried to test whether birds are indeed afraid of the snake mimic. At the time, I had a young tame Jackdaw (small corvid). When offered the big writhing worm the bird seemed confused, but then attacked the caterpillar and tried to eat it.

My trusting friend Jakob the Jackdaw

So instinctive aversion? Not really.
But: the jackdaw was young, hand-raised and inexperienced. Like young wolves, chimpanzees, and humans, the highly social and intelligent corvids are born with very little instinct. Instead, they have a great capacity for learning. In fact, this young bird looked to me for approval of any new food it found, and it would try to eat everything I offered. So he wasn't a good test animal at all, we should have tried something more precocious, like a young chicken. We just all had a lot to learn.

Macacha (Fulgora laternaria) by Leonel Baldoni
In the rainforests of central and South America lives an insect in the family of the Fulgorid Planthoppers that looks even more like a reptile than our caterpillars, at least in photos where you have no size comparison.
My friend Lois O'Brien is an expert of the group Fulgoromorpha. She writes:

"Fulgora, the lantern fly or peanut bug, has a head that looks like a peanut from above. But from the side, the head looks like an alligator head, complete with false eyes and false nostrils ...and a big mouth full of false teeth." 
To humans this planthopper looks so dangerous that there is a widespread legend that its bite kills within 24 h - the only antidote being to have sex before that time runs out. O'Brien speculates whether the 'alligator mimicry' targets birds, reptiles or monkeys, even humans, and wonders about the size difference between model and imitator. As baby alligators are quite small and quite ferocious hunters (and often under the fierce protection of their really terrifying mother), the size difference bothers me less than the difference in habitat between presumed model and mimic. But birds and monkeys get around ... and maybe they are wary enough of alligators to carry the image in their memory wherever they go.
Fulgora laternaria from Cuvier's La Regne Animal
Or maybe the mimicry model isn't an alligator but just another reptile like a lizard. In any event, the similarity seems just too suggestive to be without any function at all.
But if all else fails, Fulgora can still flash two big eye-spots at the attacker as well.

Chrysalis of Dynastor darius stygianus (photo V. Izerskyy)
 Here is another striking tropical example posted by Vladimir Izerskyy on facebook. It's the pupa of Dynastor darius stygianus which seems to be mimicking  the head of a Boa constrictor peruvianus. Dynastor darius stygianus is found in Peru, for example in Coviriali, Satipo, Peru. Clearly, the  pupa needs protection even more than any mobile form of insect, but we are more used to camouflage as the means of survival of pupas.

We found another unexpected reptile imitator closer to home:
After the black-lighting session of the last 'Infestation Party' at Pat Sullivan's house in Ramsey Canyon, Arizona, there were a lot of entomologists as well as left-over moths still hanging around in the early morning hours. The humans were congregating outside with cups of strong coffee and plates of Schwarzwaelder Kirschtorte (great way to wake up!).

Do you see the snake lurking?
At one point I bent down to take a photo of something low in the vegetation at our feet, when I heard Charlie O'Brien's warning 'Careful, there's a snake under those leaves'. And indeed, there was the eye, the shiny nose, the bigger ventral scales and the curved body of a snake - cartoonishly overdrawn but very convincing from the right angle.

But - overemphasized detail aside - I had had my morning coffee already! - so to me it was just a sleepy moth, a beautiful Glover's Silkmoth.

Glover's Silkmoth (Hyalophora columbia gloveri)

Literature: The Wild Wonderful World of Fulgoromorpha, L. O'Brien, Denisia 04, zugleich Kataloge des OOe. Landesmuseums, Neue folge Nr. 176 (2002) pp 83-102


  1. Wonderful pictures as always. I love that first moth. I posted some Elephant Hawk Moth caterpillar pictures recently and found them so fascinating close up. The Glover's Silkmoth is beautiful too.

  2. Nice story! I wish I were teaching classes that involved teaching mimicry concepts (as I used to) -- there are some great examples here.

  3. Very cool! I like the photo of you with the jackdaw! You've had some amazing experiences!