Mimicry, by Ashley Anne Wick (FFT Insect Team Coordinator)

(This blog entry is dedicated to former FFT volunteer Sofia Prado.  She never got to hear my mimicry talk because we were all frozen – like butterflies – during the epic friaje that signaled the end to our last phase).

I am a Lepidopterist.  And, for better or worse, I will remain one for the rest of my life.  I recall my father calling me his ‘little butterfly’ when I was 10, because of my constant flitting about. When I was a teenager I used to escape to a local river and observe the butterflies licking the salts of the banks. I began studying butterflies when I was 19 as head field assistant to 2 college professors.  When I was 21 I received NSF funding to study moth diversity in different forest types and in turn in relation to remotely sensed satellite data.   In 2011 I will relocate to Canada to help their federal parks system develop a plan to protect and ensure the viability of an endangered butterfly (Apodemia mormo, the Mormon metalmark) and its host plant (Eriogonum pauciflorum, wild buckwheat) as my graduate thesis.  With Fauna Forever Tambopata I currently study the Ithomiinae or glasswing butterflies in the Peruvian Amazon, with the help of volunteers from around the world.

Instead of writing strictly about butterflies, I would like to focus this blog entry on an ecological phenomenon that I encounter nearly daily, both in the field and in the lab.  Mimicry, in all its strange and diverse forms, is both a source of constant fascination and confusion. I’m often stressed out when examining two butterflies that appear to be the same species, but aren’t related at all, with one mimicking the other!  Mimicry is diverse in its evolution, forms, and strange beauty, and is never lacking in the insects, nor in the Lepidoptera (butterflies and moths).  For a simple working definition – mimicry is to appear to be something other that what one is.

Mimicry is everywhere in the natural world.  You just have to look: imagine a treehopper that resembles a thorn, a moth mimicking a bit of lichen on tree bark, or butterflies of the family Charaxinae resembling dead leaves. Tortoise beetles attach bits of excrement and debris to their body to blend into the earth and a praying mantis can mimic a flower and remains undetected until it pounces on its prey. These forms of mimicry are quite obvious – the mimics are blending into their environment.  Insects have mastered the art of camouflage in order to remain undetected by their prey (or in other cases – predators).

The previous examples of mimicry are all based on crypsis, or cryptic coloration. On the other hand, have you ever wondered why bees or butterflies are bright red, orange, yellow or dark black?  What protection would this bring against a predator?  Along the same lines, why do crosswalk guards wear orange?  Why are stop signs red?  We can assume that this bright coloration is beneficial, for evolution to have directed so many different species (humans among them) to the same set of defenses. This phenomenon is called warning or aposematic coloration.  In the case of many Hympenoptera (bees, ants, and wasps) this warning is of actual danger via a bite or sting.  In other species without the abdominal stingers of bees or the painful mandibles of a bullet ant, their coloration often warns predators of some other unpleasant experience, such as a poisonous or unpleasant taste.

In mimicry there is always a model, that model being the species that is legitimately dangerous, distasteful, or unpleasant.  On the flip side, there is also the mimic, the species that is attempting to gain protection by resembling the model.  In the following paragraphs I will present several types of mimicry along with examples, mostly from the insect world.

Batesian mimicry (named after naturalist Henry Walter Bates) is a classic example that college freshman often learn in BIO 101.  Batesian mimicry is utterly straightforward.  The mimic begins resembling (through natural selection) the model in order to gain protection from some unpleasant trait that the model has.  The classic example of this is the monarch and viceroy butterflies.  The monarch butterfly eats milkweed plants and stores the unpalatable toxins, making it taste extremely nasty to birds and other predators.  Then the viceroy buttefly, by so closely resembling the monarch in color and pattern, will gain protection from predators that have learned to not eat monarchs.  This also occurs with moths and wasps.  Below is a photo that a friend of mine took here in Tambopata.  Can you guess what it is?  If you said a wasp, you have been duped, like many intelligent birds before you.  This is actually a moth in the family Sesiidae!

The second most well-known type of mimicry is Mullerian mimicy (after Fritz Müller).  In this type of mimicry, multiple unpalatable or otherwise harmful unrelated species will mimic each other, with all individuals involved serve as both mimics and models at the same time.  What benefit would all individuals gain by all being distasteful or dangerous and mimicking each other?  Let’s take tiger colored butterflies for an example.  If a bird successfully eats one bright orange, yellow, and black colored butterfly and has an unpleasant experience, it is likely to avoid all similar looking butterflies in the future, in turn, all tiger butterflies would gain protection from the single fatality, magnifying the impact of a single death. This ecological phenomenon can also be described as mutualism.  (www. On mullerian france museum mimicry rings).

Now, let us examine some lesser-known types of mimicry – Wasmannian, Gilbertian, and Aggressive mimicry.

Wasmannian mimicry – which occurs when a mimic resembles a model along with which it lives.  Due to limitations of cohabitation, this usually occurs with insects that live in a social setting, like ants, termites, and wasps.  This is sometimes the case with beetles or spiders attempting to gain protection by living in the nest of ants or termites. As an additional note, many social insects have the advantage to being an excellent model, because they are known to be able to mount extensive attacks due to their social behavior – this can add an additional benefit to the mimic of ants.

Gilbertian mimicry (named after Lawrence E. Gilbert) occurs when a host or prey attempts to defend itself by mimicking its predator or parasite. The most well-known case of this is between Heliconius butterflies and plants in the genus Passiflora. The story of these two groups of species that have been interacting is incredibly interesting, but I’ll let you judge for yourself.  As a result of herbivory of the larvae of Heliconius, Passiflora have developed toxins to deter herbivory.  In response to these toxins, the larvae have evolved enzymes which break down the toxins, allowing them to continue to feast on the foliage of its host plant.  As an even more extreme response to the continued herbivory, Passiflora began to evolve stipules that mimic nearly hatched Heliconius eggs.  The adult butterflies would likely avoid plants that already have mature eggs which would eat the leaves before their young would have a chance to hatch, and even avoid the potentially cannibalistic behavior of Heliconius larvae. One must wonder: What is next in the evolutionary game for these two groups of species?

Aggressive mimicry, also called Peckhamian mimicry (named after George and Elizabeth Peckham), occurs when a predator mimics a model, but the model is not necessarily its prey.  This type of mimicry is common in many different types of fauna, and may be detrimental, negative, or positive for the model. Let’s look at a couple quick examples of this strange manifestation of mimicry.  An Australian katydid finds prey by luring in male cicadas.  It does this by using the same species-specific clicks that female cicadas use to attract males, and once the katydid has succeeded in attracting the male cicada, it will feast. The katydids are able to change their clicks to mimic different species, even those with whom they do not normally coexist.  Another example, and a shout out to the birders out there, we shall investigate an avian example of aggressive mimicry.  The zone-tailed hawk, which resembles the turkey vulture, will sometimes fly around with vultures.  Being a predator, the hawk will quickly break formation and attack an unsuspecting prey in a tree or on the ground.  What is interesting about this example of aggressive mimicry, is that the turkey vultures are neither positively nor negatively affected by the presence of the hawk.

Hopefully you have enjoyed learned about a few of the thousands of examples of mimicry in nature, and here in the rainforests of the Tambopata it is nearly impossible to not take notice of the diversity of insect size, shape, and behavior.  I hope that you too can appreciate the intricacies and beauty of insects and how these tiny creatures have evolved to compete and thrive in the natural world.

Want to know more about mimicry, butterflies, or volunteering with my research in the Amazon? Email ashley@faunaforever.org or check out www.faunaforever.org/fft

References:

Insects of Latin America

An Introduction to the Study of Insects

Bugs in the System

Brittanica Online

www.Bugguide.net “Arthropod Mimicry”