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'Any color you can do - insects can do better'

February 9, 2018
Blue Tick

I have dedicated my whole professional life to defending and extolling the virtues of insects. Insects are incredible organisms and I have little trouble playing the “anything you can do, insects can do better” game. It is not hard to find insects out-performing just about any other animal in just about any category.

 However, a recent question sent me into research mode: Do insects have the ability to change color like a chameleon — rapidly and intentionally altering their color to blend into their environment for camouflage, to avoid predation or to attract mates?

 Insects are known for their beautiful colors. They rival birds, reptiles, and even fish with their beautiful and vibrant colorations, varied patterns of spots or stripes or splotches and some even have distinctly iridescent or metallic colors.

 Fish (such as the peacock flounder and some mollusks including squid, octopuses, and cuttlefish can quickly and dramatically change colors by either concentrating or dispersing pigments in their skin cells.  Reptiles, most famously chameleons, change the color of their skin by adjusting iridophore cells containing certain nanochrystals that selectively reflect various wavelengths of light.  But what about insects? Can they change colors?’

I found examples of a couple of Australian crab spiders that can change color while hunting. They change their color to replicate the color of the flower they sit on. Unsuspecting bees or butterflies cannot see them, and just as they prepare to pollinate the flower, they become instant fast food.

Even better, I found an example an insect that is a close cousin to the golden tortoise beetle, which is common throughout eastern North America. It is able to turn from its normal, iridescent golden color to a scarlet-red and then back again, almost instantaneously.

Exactly why it does this may be a matter of conjecture — possibly better suited for another column — but it is sufficient to mention that scientists only observe this color change at two times: when the insect is violently disturbed or when it is mating. Anthropomorphically speaking (which means ascribing human emotions to non-human animal behaviors), I can personally understand why the beetle would turn red during these times.  I suspect it is either rage or embarrassment. I know because I am told that I turn red if I am very upset, during a strenuous workout or during strenuous romance.

But how do tortoise beetles accomplish this color change given that their hardened exoskeleton is drastically different than human, fish or reptile skin. Instead of blushing or physiologically altering pigment or nanocrystal containing cells in the skin, the Panamanian golden tortoise beetle changes colors using an entirely different strategy.

According to the insect scientists who studied this phenomenon, the beetle’s outside shell or exoskeleton has three layers, arranged one on top of the other. Each layer reflects light of a different color or hue. Combined, these reflections produce the beautiful and characteristic gold color for which golden tortoise beetles are known. However, beneath this outside shell is a layer of distinctly red pigmented tissue.

Under high power microscopy, scientists discovered that each of the three outside shell layers is, in fact, composed of tiny grooves that insects fill with clear body fluids. When filled, the shell is smooth and acts as a "very effective mirror," that reflects most sunlight and makes the beetle appear shiny and metallic gold. However, when the grooves are empty of fluid, the outside shell becomes less reflective, almost transparent and acts more like a window than a mirror. When the shell loses its reflective properties, the gold hue fades, revealing the dull, red color underneath.

So, anthromorphically speaking, this insect has the ability to show its true colors (whether it is feeling irritated or romantic) by controlling the amount of liquid it forces into its shell grooves.

Fascinating stuff! Proof that these beetles encased in exoskeletons can show rage or even blush even though they lack the physiological processes we humans use. Insects never stop surprising us with curious solutions to everyday problems.

And, brilliant work on the part of the researchers to discover this. Congratulations to them on publishing this important work. While I was not invited to be part of their particular research team, I did have a discovery of my own that relates to insects and how they can change color. My finding may not be as scientifically acclaimed or as ground breaking as theirs but, hey, it is my contribution to science and perhaps others can all learn from it as well. Since I was not invited to add my findings to their paper, I’ll publish it here.

This came about by way of a question from a gentleman who found what appeared to be a tick attached to his leg. He noticed it while fishing in the creek that ran through the back of his property.

 He began, “I have lived in Indiana for my whole life and in all my time I have never seen anything like this before. Once in a while I find a tick on me or my dog. I just pull them off. But I thought ticks were supposed to be brown or black. This one is bright blue. So, is it a tick or something else — like a rare, mutated, prehistoric, never-before-seen thing? Maybe new to science?”

 I often get questions about ticks on people or on pets. They are common during the spring and summer. Almost all of these ticks belong to one major family called often called hard ticks (Ixodidae). Adult tick sizes vary by species, but all are less than an inch long, have 8 legs and large protruding mouthparts at the tip of their characteristically pear-shaped body. Normally, a tick’s body is flattened, top to bottom, but can swell enormously when it engorges on its host’s blood. All ticks that I know in are reddish-brown. Never, ever, blue.

 Thinking this might be a practical joke (some people like to tease entomologists this way) I decided to play along. I sent a note back saying that the behavior sounded like it could be a tick but as to the color I could only speculate. Maybe it was just a tick that was having a bad day and feeling a bit blue, or maybe it was a bluetick hound dog tick, or perhaps it was a tick that had been feeding on a smurf. I requested that the tick be immediately submitted for physical examination. I chuckled to myself at my clever response, never expecting the specimen to be submitted.

 However, it was. When the specimen arrived, it was the exact shape and size of a tick. It met all of the tick identification requirements perfectly — except that it was blue, in fact, bright blue. But something about it was not quite right.

 I put it under my microscope and noticed that the blue color, which completely covered its back also extended to parts of its legs but not all. This was suspicious. I probed the cuticle of the tick and found that I could actually peel the blue color back, almost like paint. Almost, exactly like paint.

 I sent my final report back saying that this was indeed a tick but it appeared to be artificially painted blue and then I questioned how that might have happened.

 A few days later I received a photo of a piece of wooden furniture sitting on a work bench in a back yard. The somewhat sheepish accompanying note read, “My wife recently repainted this bookcase. It is on the path to the creek where I fish. Could it be the cause?”

 The color match was perfect.

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