Learn how camouflaged insects and birds are able to protect themselves in nature.
In nature, things are not always as they seem.
The firefly, a male Photinus pyralis, winks his best
come-on wink as he flies through the summer night: Turning
on his light for precisely half a second while swooping
Light off, he cruises seven seconds, then — swoop,
blink, another “j.” Over and over, he trips his light
fantastic in seven-second cadence. On the grass below, an
appreciative female answers each “j” three seconds later
with a half-second glow, a response that identifies her as
a P. pyralis too, and a willing one at that. Encouraged, he
draws near and lands next to his newfound mate. The female
turns to him, grasps him in her forelegs — and,
crushing his body between powerful jaws, devours her
would-be lover’s juicy innards.
Such are the dining habits of female Photuris fireflies, a
whole different genus. Having cracked the code of the
others’ love talk, they lure in tasty Photinus
males — and meals — by mimicking the come-hither
flashes of Photinus females.
Sneaky? Yes, but hardly unique in nature. Mimicry — the
practice of imitating something you’re not to gain some
kind of advantage — is widespread. Bugs do it, birds do
it, reptiles and amphibians and even mammals do it. It’s a
predator-eats-prey world out there, and a little evolved
trickery can mean survival.
Camouflaged Insects: Hiders and Hollerers
The simplest form of mimicry is Camouflage. The fundamental
idea with camo, though, is not to imitate some other
creature, but some other thing. The benefit in a locust
treehopper resembling a locust thorn, a toad the pebbles on
which it hops, a snake the leaves in which it slithers, is
plain. A predator is less likely to bother you when you
seem inanimate and inedible.
Not all pretenders in nature are duck-and-hide types,
however. Others have evolved quite the opposite strategy
and wear bold patterns and bright colors.
In some cases the patterns serve to create a momentary
diversion. Scientists suspect that the lines around the
edges of butterfly wings, for example, look like
caterpillars to birds. Pecking for a meal of luscious
larva, the bird winds up with a beak full of dry wing
scales while the butterfly flutters away — tattered,
perhaps, but alive.
The round “eye spots” on the wings of many moths and
butterflies produce a Similar effect. Most insectivores go
for the head —the nerve center — to subdue their
prey. Aiming for the “eyes,” a predator merely punches a
hole in a wing and gives its quarry time to flee.
Eye spots can play another deceptive role. At rest, a
large-winged moth or butterfly may seem a tempting target.
But when a predator comes too near, the insect has a
surprise in store. Opening its wings, it flashes its large
eye spots — “Boo!” Startled by the sudden appearance
of an animal’s face, the predator leaves in a hurry.
Other creatures also sport distinctive designs and colors
intended to frighten — but it’s no act. Their colors
are a fair warning, loud and clear: “Here I am, and I’m
bad. Steer clear if you know what’s good for you.”
Many animals and insects that taste awful, sting or can
otherwise turn a good day sour have adapted this
warning-label strategy, known as aposematic coloration.
It’s effective, too — just check your own reaction next
time you encounter a small, furry four-legger with white
stripes clown its black back and tail. You’re outta there.
Who’s Fooling Whom?
Warning colors work by teaching predators hard lessons.
When you take a bite of a yellow-and-black-striped buzzing
thing and — Ouch! — get stung, you tend there-after
to avoid putting yellow-and-black-striped buzzing things in
your mouth.
This explains, at least partially, two phenomena: (1) why
many of the bees and wasps you see rear similar yellow and
black stripes, and (2) why there’s a good chance at least
some of the “bees” and “wasps” flying around couldn’t hurt
a fly — and may, in fact, be flies.
A variety of insects, including some beetles and moths,
mimic hoes and wasps. The most common impostors are the
syrphid flies: nectar-loving hover flies, drone flies and
more. Most syrphids are fat, fuzzy and buzzy like bees;
some are slim and hardbodied like wasps.
The supposition, of course, is that the unarmed and
perfectly edible insects have, over the eons, developed the
same striped uniform as the bees and wasps for defensive
purposes. Predators that have learned a painful lesson from
the real stinging thing will avoid the impostors, too.
In scientific circles this idea — an edible species
benefiting by imitating a noxious one — is known as
Batesian mimicry. It’s named after Henry Bates, a mid-1800s
naturalist who roamed Brazilian forests collecting
butterflies. Bates noticed that in many cases two
similar-looking but different species shared distinct
colors and patterns. He theorized that one species tasted
had and kept predators away by advertising its
patooey presence. The impostor species gained the
same advantage even though it didn’t taste bad.
You may have learned all about this in biology class.
According to recent research, though, you may not have
learned it exactly right. Mimicry, it turns out, can he as
tricky as the pretenders themselves.
Take the oft-cited classic case of Batesian mimicry
involving the dead-ringer resemblance between monarch and
viceroy butterflies. For decades scientists thought that
all adult monarchs carried within them the hitter
aftertaste of their larval-stage milkweed diets, and thus
were Unpalatable to birds and other predators. Viceroys
were thought to be the edible mimics who benefited from the
monarchs’ distasteful reputation.
But when a graduate student at the University of Florida
tested the notion by offering the bodies of both types to
hungry blackbirds, he found — much to the scientific
community’s surprise — that both types taste had to
birds. This kind of mimicry, in which both look-alike
species are noxious, is known as Mullerian mimicry. There’s
no fraud involved, but both species benefit because
predators nibbling at either learn to avoid the other, too.
Unfortunately, it turns out the monarchs and viceroys can’t
be netted into that neat category, either. Further studies
suggest that some monarchs and some viceroys are palatable,
while others are not. So who’s mimicking whom, and why?
Listen carefully, and you may hear the faint sound of
puzzled biologists scratching their heads.
Likewise for the aforementioned syrphid flies, long
considered obvious and classic mimics of wasps and bees.
Naturally any bird that bites a bee is going to learn in a
hurry to avoid all bee-like insects.
Well, yes and no. Scientists now know that many birds with
eyesight sufficiently keen to discern striped
patterns — phoebes, swallows and martins among
them — gobble up bees and wasps with apparent relish.
Not surprisingly, they’re quick to make meals of syrphid
fly look-alikes, too. So what would he the advantage of
mimicking?
Further Studies have provided at least a partial answer.
Some birds, it seems, are indeed susceptible to stings and
learn the hard way to react with “yipes” to stripes. Crows
and starlings are among birds that avoid both the real
thing and syrphids. Perhaps more significantly, toads and
frogs also keep a tight lip — and a coiled
tongue — when it comes to the insects. So the syrphids’
mimicry does indeed serve a purpose. Its not exactly
surefire insurance against predation, as was once thought,
but it does up the odds in the flies’ favor.
Mimicry, it seems, teaches humans a dual lesson: In nature,
you can never be sure of what you see . . . or of what you
think you know.
