A reader called recently to tell me about a large bug that appeared near her backyard fish pond. My first guess was a giant water bug because they leave ponds occasionally and are attracted to light. This insect was, however, not that species at all. It was an eyed click beetle or eyed elater, a species with two interesting characteristics each of which serves in the insect's defense.
The first is apparent in the illustration. Those large circles look like eyes and they make this inch-and-a-quarter long insect look like the head of a much larger creature, perhaps a snake. Would that be enough to make a predator hesitate? It might be just enough to give the species an evolutionary advantage.
But this beetle enjoys another quite remarkable defensive edge. In order to describe this feature I first remind you of the three major body parts of insects: head, thorax and abdomen. On this beetle the head is much smaller than the other two and sports those antennae. The next part, where those false eyes are on this specimen, is the thorax. It is a bit like our chest and has this beetle's wings and legs attached. The abdomen is the rest, more than half of this insect's body.
What is special about click beetles (there are hundreds of species) is that the connection between their thorax and their abdomen is flexible and, if the insect is turned on its back, it bends those two body parts and hooks them in this stretched position with a spine. With its thorax and abdomen pulling to return to their normal position, the beetle suddenly releases that spine. The result is like snapping an upside down mousetrap with the beetle flying six or eight inches into the air.
This very sudden action could be just enough to startle a predator and allow the beetle to escape. It might even fling the beetle into cover where it could hide.
Like so many activities nowadays, you don't have to experience this one in the real world. You can watch someone else making a click beetle perform this strange trick on the web at www.youtube.com/watch?v=uH4roWTUMoA.
These are, of course, only two of the defensive tricks used by animals to avoid becoming the prey of a larger predator. They need these defenses because it is not easy living well down on the food chain.
Perhaps the most common response is simply to hide. Some animals like salamanders spend most of their lives buried under leaves and duff on the forest floor, emerging only to mate in the spring. But other animals need time in the open to feed. Many of them adopt a hide-in-plain-sight defense: their body shape or coloration serving as camouflage.
Perhaps the most famous of these are chameleons and octopuses that change color to appear like the surface on which they are resting. But there are many less extreme versions, from walking sticks, insects that are almost impossible to differentiate from the twigs around them, to moths whose coloration matches the tree trunks on which they are found.
Several times I have come upon fawns curled in the undergrowth, their soft brown coats broken up by lighter spots making them almost impossible to differentiate from their surroundings. These dainty little animals remained still even when I approached to within a few feet. Awkwardly running from most of their predators on their still spindly legs would not serve them; they were forced to trust in this one defense. When I finally reached down and touched one, it finally rose and hobbled off to join its mother a few yards away. I read into the doe's sad eyes a kind of thank you for not harming her offspring and I knew that she would make her fawn hide again the next time danger approached.
You probably know some of the many other unusual defenses: The opossum and hognose snake that play dead. In doing so the snake lies on its back, but if you turn it over it flips back again, a clear example of a flawed inbred response. Bombardier beetles that squirt near boiling water at their enemies. Skunk's smell, porcupine's quills, bee's stings,...
To attack these animals their predators have to find a way around these defenses or in some cases suffer the consequences.-- Gerry Rising