INSECT CAMOUFLAGE-NOW YOU SEE THEM, NOW YOU DON’T!

In nature, survival is the name of the game. Over the millennia, animals have evolved countless ways of avoiding danger, especially to defend themselves against predators. Insects in particular have a stunning array of defenses at their disposal. They run, jump, fly, bite, sting, and pinch. Many have bodies coated with itchy hairs or bristling with sharp, painful spines. Others have bright, conspicuously colored bodies that warn potential predators of their bites, stings, or foul tastes. Some are mimics, sporting the colors and behaviors of pugnacious, bad tasting species, but are in fact harmless themselves. But most insects protect themselves by simply remaining out of sight. And many of them do this with camouflage.

Camouflage, the French word for disguise, first appeared in popular English usage in 1917. To many, the word camouflage brings to mind the color patterns used on military combat uniforms and armaments, patterns that have since been adopted as the “official” garb of many anglers and hunters. But these and other uses of camouflage were all inspired by examples in nature, especially insects.

The simplest type of insect camouflage involves having body colors and patterns that help to conceal their bodies against specific backgrounds in their environment. For example, the leafy green hue of some praying mantids helps them to blend in among shrubs and low growing herbaceous vegetation.  In other species, such as the Carolina mantis, gray individuals are better suited for concealment on tree bark. The cryptic lifestyles of these and other predators help them to mask their presence from both predators and prey.

Toad bugs are small, squat, bug-eyed predators with grasping front legs. They hop along the shores of streams and lakes in search of small insect prey.

Toad bugs are small, squat, bug-eyed predators with grasping front legs. They hop along the shores of streams and lakes in search of small insect prey.

The shores of streams, rivers, and beaches are frequently occupied with ground dwellers whose body colors and textures are perfectly adapted for living concealed lives along the edge. One of my favorite examples is the aptly named toad bug. These small, squat, bug-eyed predators with grasping front legs hop about the wet sands and fine gravels, ever ready to pounce on even smaller insect prey.

Some grasshoppers and caterpillars have the ability to change their colors to match temporary backgrounds. Locusts can adjust their colors to match dry, open ground or lush, green vegetation. Many caterpillars avoid detection by using counter shading and are usually lighter below and darker above.

Papilio001

Not all cryptic species of insects resemble rocks, sticks, or leaves. The early stages of spicebush swallowtail caterpillars have white and black blotches on their body that makes them look like a bird dropping.

The colors and patterns of these and other insects have developed gradually through the process of natural selection. Individuals that avoid detection by predators through camouflage are able to pass along their favorable traits to their offspring generation after generation. Over time, this continual fine-tuning eventually results in colors and patterns that are ideally suited to enhancing their survival in a particular habitat. But effective camouflage isn’t just about matching colors and blending in. It is also about breaking up the outline of an insect’s body so that it looks less like a prey item to a hungry bird or lizard.

Diaphemora002

Stick insects look and behave like a stick. During the day stick insects remain almost motionless, lest they give their position away. But sometimes they will gently rock back and forth, as if they were swaying in a breeze.

Another camouflage tactic is to match the color and look of specific objects in the environment. This form of camouflage is called crypsis, a word derived from the Greek word kryptos, meaning to hide or conceal. Cryptic insects not only have the same colors as sticks, leaves (living or dead), and rocks, but their bodies are also shaped to look like them, too. Hungry predators pay little attention to these and other seemingly inedible objects when they are on the prowl for flesh.

Effective crypsis is more than just looks; it’s also about behavior. Cryptic insects have to select the right background and orientation so that color and form blend seamlessly into the right background. Landing on the wrong place, or settling in the right spot but in the wrong direction will inevitably lead to discovery and death.

geometrid larva001

With its stiff body and gray, bark-like skin, this geometrid moth caterpillar is a dead ringer for a twig.

Once, while walking down a path, I saw a twig-mimicking caterpillar stiffly protruding from the middle of the pavement.  Its gray, warty skin was a dead-ringer for a twig. Had it been on a tree or shrub, I never would have noticed it. But for whatever reasons, it had decided to conspicuously take its defensive pose out in the open on a flat, black background.

Phyllium001

The java leaf insect, cousin of the stick insect, has a flat, leaf-like body covered by a pair of leaf-like wings, all supported by six leaf-like legs.

Some of the most stunning examples of insect crypsis are species found in tropical rainforests. It is not uncommon to see these insects utilize every part of their body to help them look like something else. Java leaf insects, cousins of stick insects, have a flat, leaf-like body covered by a pair of leaf-like wings, all supported by six leaf-like legs.

dead leaf katydid001

This Costa Rican katydid is a dead leaf mimic. Note the markings on the wings suggesting the veins of a leaf.

Of course, no defense strategy is 100% effective. Birds and other sharp-eyed predators can pick up the presence of cryptic insects by their symmetrical shapes. Tropical katydids have gotten around this by having asymmetrical wing shapes and patterns. Each forewing has its own set of spots and notches suggesting leaves that have been randomly attacked by insects and fungus.

Sometimes symmetry is detected by the narrowest of shadows. Many cryptic insects purposely avoid casting shadows by pressing their bodies and appendages tightly against the substrate. Others have fringe lining their bodies and appendages that eliminates shadows altogether.

Every time I go out in search of insects, I am continually fooled by bits of vegetation that appear at first glance to be a cryptic insect. But every now and again I am rewarded for my efforts with yet another surprising example of insect camouflage. This and other revelations are constant reminders that there are lifetimes of insect discoveries to be made.

©2009, A.V. Evans

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14 Responses to “INSECT CAMOUFLAGE-NOW YOU SEE THEM, NOW YOU DON’T!”

  1. […] Arthur Evans discussses insect camouflage. […]

  2. A type of camouflage that has been derived several times in soil mites is a sticky outer covering to which the mite attaches soil or detritus particles. Some use clay-sized mineral particles and ‘mud’ themselves in completely except for cracks at joints; others stick a variety of organic debris to their bodies. Since most of these mites are eyeless and live in the soil (not much light there). I’ve always assumed this was more a tactile than a visual camouflage, but small birds, lizards, and apmphibians do eat these mites, so there may be a visual benefit too.

    I remember seeing pictures of an assassin bug that preys on termites doing something similar, and caddisflies also come to mind, but I wonder how common mudding up is in the Insecta?

  3. Great stuff. I love that java leaf insect!

  4. A FEW YEARS AGO WE FOUND A CATERPILLAR IN OUR BATHROOM THAT USE A MUDDING TECHNIQUE AND COVER IT’S BACK WITH FRAGMENT OF A BRIGHT GREEN TOWEL, THEN A FEW WEEK LATER WE FOUND THE SAME TYPE OUTSIDE ON OUR STOOP COVERED IN LEAF FRAGMENTS. NEVER TO SEE AGAIN. DOES ANYONE KNOW WHAT TYPE OF CATERPILLAR? iT WAS SO FUN TO SEE THE TECHNIQUE INSIDE THE HOUSE AND OUT.

    • Arthur Evans Says:

      Thanks for your note. There are several species of case-bearing caterpillars. I am not sure which species is the one you have described. One of the usual suspects in the home is the case-bearing clothes moth. The larvae use bits of material to form a protective bag around their body.

  5. Dotty Rilee Says:

    Art, I’m enjoying your blog & 2 weekends ago was a fantastic experience watching you collect & identify bugs at the Rice Center. Thanks alot for letting Elli and me be part of that!

    Last week our youth adventure camp caught some bugs & we used your new field guide to identify them! They loved it! They found a ground beetle, cucumber beetle, then we got stumped on what we think was a beetle and also a locust. (or cicada?)

    If you have time I’d love to make an insection collection for my class with your leftovers!

    Thanks again!

    Dotty

  6. I am having trouble locating any type of picture to tell me what kind of caterpillar I found outside my house in West Texas. It was your average light green, about 1 1/2 to 2 inches in length and had the appearance of a leaf. You could see how the skin resembled the veins and it had a little stump at it’s rump that looked like the stem of a plucked leaf. It was quite interesting to see, and I wish I had snapped a photo of it, but I didn’t. Any help identifying this little guy would be greatly appreciated!

    Thanks
    ~M

  7. I seen a very strange bug on my railing of my deck today. it was a very small white thing with about 6 or 8 short legs and carried a “awd” of what looks like grass and dust on it’s back. I thought it looked like a “walking dust bunny”. lol. What is it?

  8. What a great resource. Thanks so much for the information and amazing pictures.

  9. Ken Harmon Says:

    Those grasshoppers are spectacular! I never even knew such colorful species existed! Do you have any more pictures of the greenhouse stone crickets? I love them but have never managed to get any crisp snapshots of them. I’d like to model one. Any angle would be great. Congregations of them would be cool too 🙂 Thanks!!

  10. This is a topic which is close to my heart.
    .. Many thanks! Exactly where are your contact details though?

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