Insect acrobats

StoryImage( ‘/Images/Story//Auto-img-115999476511368.jpg’, ‘Photo by Dr. Robert A. Hedeen’, ‘The click beetle, known as the eyed elator, is the best known of this large group of insects.’);

There is hardly a youngster who has ever been exposed to the outdoors who has not been entertained by the acrobatic performances of the elongated, streamlined beetles called snapping bugs, skip-jacks or click beetles. If you touch one of these insects, it immediately curl up its legs, and turns over on its back. For a time, it will maintain this posture as if dead. Suddenly, there is a click or snap, and the beetle will pop inches into the air, spinning end over end.

If it lands on its back, it repeats this gymnastic maneuver time and time again until it succeeds in landing feet first. Then, tiring of the “game,” it will scamper off to a place of concealment. Mischievous boys (and sometimes girls) entertain themselves by catching a click beetle and placing it on its back again, thus prolonging the circus.

The clicking sound and vertical movement are made possible by the loose connection of two parts of the insect’s thorax and a spine located in a groove on the undersurface. When the bug is placed on its back, it is usually able to right itself by manipulating its legs, but if this does not work, the clicking technique is employed. To do this, it bends its head and rear end backward so that only the extremities of the body are touching the ground. A sudden jerk, accompanied by the “click,” straightens out the body, and the spine is propelled downward, and the beetle is hurled into the ozone.

The family of click beetles is quite large with about 850 different species reported from North America alone. Most are rather small, but the large eyed-elator may reach a length of 2 inches and is the best known of this diverse group. This common clicker is readily identified by two large, back “eye spots” on its back against a salt and pepper background. These spots are not eyes, however, as the true eyes are small and located at the base of the antennae or feelers.

As noted, most click beetles are much smaller than the “eyed” variety and are inconspicuously colored brown or black to blend in with their habitat. Some tropical click beetles, however, have luminous areas instead of eye spots. A number of these in Puerto Rico are called automobile bugs as the luminous areas resemble the headlight of a very small car. The light emitted is much stronger than that generated by lightning bugs or fireflies and is produced by a series of complex chemical reactions that are not completely understood. The production of luminescence is associated with the mating process. It is reported that luminous click beetles are used as ornaments by ladies in certain tropical countries.

The larvae of some click beetles live under the bark of trees and in rotted wood, but many inhabit the soil and feed on seeds and the roots of a variety of plants. They are elongated, cylindrical, worm-like creatures and are yellowish in color. The hard outer covering has given rise to the common name for these larvae—wireworms. There is hardly a plant that they do not attack, and living underground as they do makes control difficult, except with strong insecticidal formulations. Beans, cotton, corn, potatoes and cereal grains are favored crops attacked by wireworms. Not only do they damage a variety of plants, but they tend to attack the plants at their most vulnerable time of growth, before they have attained sufficient size to resist. Thus, a farmer’s field may be severely damaged shortly after the seeds he has planted germinate.

Click beetles are just one of the countless insects of economic importance man has to contend with, and a farmer with a devastated crop is not likely to be amused by the clicking and jumping antics of click beetles.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

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