Blistering
beetles bemuse
Caution: caustic chemical cantharidin
By Callan Bentley
Flat Hat Variety Editor
You can tell that summer is only a short time away because of the sudden profusion of insects. This was what I was thinking last week when my roommate called out to me.
"Callan," he said, "There's a big bug over here. Do you want it?"
I grabbed an empty coffee mug and scooped up the visiting insect. The "bug" was a beetle of some sort. True bugs are in the order Hemiptera, whereas beetles are in the voluminous Coleptera. But what sort of beetle was it? Insects are the most numerous animals in the world, and beetles are the most numerous of all insects, with about 200,000 species in the entire world, and 25,000 in North America alone. This could have been any of 200 different species, for all I knew.
Fortunately, I have a copy of the Peterson Field Guide to Beetles on my bookshelf. By matching the insect's body size, metallic green sheen, and long legs to the descriptions in the book, I figured that the beetle in my coffee mug must be Carabus scrutator, a ground beetle (Family Carabidae) called "the fiery searcher." I learned that it is an important predator of caterpillars, and is the largest member of its family on the continent.
Impressed, I let the beetle go out an open window. I told a biology major friend of mine about the fiery searcher's visit, and he responded by informing me that a similar beetle had stopped by his room that evening too. He described it: black, over 3 cm long, with long legs and bluish-green elytra ("elytra" are the beetles' shell-like wing coverings). We drew pictures to compare what we had seen. It was the same species of beetle, no doubt about it.
Wondering at this coincidence, I went back to my room and resumed my studying. After another few minutes had passed, my other roommate told me that another "bug" had flown into the room. I saw that it was another fiery searcher beetle, but before I could catch it, the insect had crawled under a bookshelf, out of reach.
Later, while answering the phone, I saw another one. This totaled four of these beetles in a single hour. I puzzled delightedly. Why were they coming into my dorm? The lights? The open window? Why all at once? Perhaps they all hatch at the same time, I thought. This would make sense, since beetles usually have a single life generation per calendar year. Larvae metamorphose into adult beetles in the spring, and so it's reasonable to expect them to be showing up about now.
The beetles in general hold a great many mysteries like this. With all that variation among so many species, it would be hard not to.
For instance, the meloid beetles (Family Meloidae), also called "blister beetles," secrete a chemical called cantharidin. When these beetles are disturbed, they exhibit a "reflex bleeding" response, where droplets of their blood are exuded at the kneecaps or other parts of the body. This is what scientists term autohemorrhage, meaning that the beetle causes itself to bleed, and injury is not causing the discharge. The blood contains cantharidin, which causes blisters upon contact with human skin. Interestingly, the supposed aphrodisiac Spanish Fly is made from the crushed bodies of meloid beetles.
One sure sign of summer's arrival will be the presence of "lightening bugs" or "fireflies." You will not be surprised to learn that these are neither bugs nor flies, but beetles of the family Lampyridae. They are quite well known for the luminescent ability of their posterior-most abdominal segments. Most children find this fascinating. Like my childhood neighbors, I spent many summer evenings outside stuffing lightning bugs into a glowing mason jar. The flashes of light are used to let male fireflies locate female "glowworms" (which are wingless) on the ground. Each species of firefly has its own distinctive series of flashes, which vary in intensity, color, and frequency. Occasionally, females will imitate the flash sequence of a different species and then eat any hapless males with are attracted to her.
Beetles can be found anywhere
and everywhere. This summer try to dedicate yourself to learning more about
the natural world. Instead of watching MTV some evening, pull out the old mason
jar and go after the fireflies. Inspect the fiery searchers of your life with
your own searching curiosity. Like each person you meet, each insect has a unique
story. With fascinating tales to be told, all you have to do is ask.