Background Essay: Evolution of Camouflage
In the insect world things are often not what they seem, especially if you're a hungry predator. For 250 million years, insects have survived because they often appear to be something other than what they really are. Is it a bug, a twig, or a leaf? Is that butterfly the bitter-tasting one, or the delicious one that resembles it? An astonishing number of insects have evolved survival mechanisms that involve mimicry, camouflage, and disguise.
In the case of orange-and-black butterflies, the viceroy has evolved a striking resemblance to the beautiful but foul-tasting monarch. The two are so similar that predators -- mainly birds -- avoid the viceroy, which is actually quite tasty but has benefited from the unpleasant reputation of the monarch.
Sometimes the mimicry is not visual but auditory, as in some harmless flies that emit a sound just like the buzzing of an angry bee or wasp, keeping attackers away. Another, more unusual variety of camouflage is "aggressive mimicry." Some insect populations have evolved to mimic another species' look or behavior, which allows them to get close enough to an unsuspecting bug to attack and eat it.
When an insect happens to blend in with its environment, it's called camouflage. Like mimicry, camouflage can be "protective," to avoid the attention of predators, or "aggressive," to allay suspicion while the predator attacks its prey. The praying mantis that has evolved a flat, triangular shape and coloring just like the leaves it sits on is extremely hard to detect.
In camouflage, the shape and outline of the animal merge with the background so it's not recognizable. Similar to camouflage is disguise, in which the entire insect looks like a specific object, like a leaf or a twig that predators overlook. For these strategies to work, the animal must stay in a particular position for hours at a time, like moths that are active at night and rest by day, sitting motionless on the tree trunks into which they blend.
Some creatures even change color to blend with new surroundings, like the crab spider that changes from white to yellow when it moves from daisies to goldenrod in the summer. With this in mind, it's certain that the forests and fields are alive with thousands of insects we never see -- but might, if we knew what to look for.