Once in awhile my cat seems to be taking a curious interest in something on the kitchen floor, and from a distance it would seem she is chasing vapors or ghosts, because nothing is there. But, as I walk into the kitchen to save her from herself I realize that a fascinating new toy has brought itself to her, and it is bouncing around on the hard surface of that floor. It is a click beetle, a member of the beetle family Elateridae, whose members are found all over the world and constitute some of the most colorful beetles there are. All of the species have a typical appearance for the family, as elongated and somewhat flattened beetles that we describe as “boat shaped”. They range in length from tiny ones only 1/8 inch long to species that may top out at nearly 3 inches in length. Tropical species can be of a variety of metallic or nonmetallic colors, and even in the United States we have some kinds that are metallic blue or green. Some kinds have artificial eye spots on their thorax to frighten potential predators, and others have light producing organs on their thorax.
What gives them their common name though – “click” beetles – is their ability to snap up in the air when they find themselves flipped over on their backside. With relatively short legs they have a difficult time grabbing onto something as they flail away, and finally tire of the attempt. At that point they simply bend their head and first section of their thorax forward, forcing a spine on their underside to slip into a groove in the second section of the thorax. Then as they suddenly bend the head straight again that spine SNAPS out of the groove and causes them to bounce off the surface. It may not be successful the first or second time, but eventually they land on their feet, and are off and running again. There is an audible CLICK as that spine snaps out of its groove, and of course on a hard surface it may be a continual snapping and clicking until the beetle has righted itself. Some of the smaller brown species, those most often getting into my own home, may bounce several inches off the surface, driving the cat crazy as it attempts to capture the elusive toy.
The adult beetles are often active at night, and may be attracted to porch lights. As someone opens the front door they may fly in or may just wander under the door if there is any sort of a gap for them. These are small and flat beetles, and it doesn’t take much of an opening to admit them. Once inside the home there is no danger to people, pets, furnishings, clothing, food, or the home itself. These beetles are harmless to people. They do not bite or sting and can be handled safely. They do not infest anything in the home, and would eventually die if they are trapped inside. The larvae feed on various things, one of which may be the roots of plants, and these larvae are referred to as “wire worms”. They are long and thin and shiny, and when their numbers are high may cause some serious damage to plants and their underground parts. They are known as pests when feeding on the roots of beans, cotton, corn, or potatoes. Around the home, though, they generally occur in lower numbers and any feeding on plants appears to be of little consequence.
The larvae, however, can be a real nuisance, and became noteworthy in northern California, at least, on hot summer days. Where the temperatures may reach well over 100 degrees for days on end things tend to dry out, and it is during these hot stretches that we now get annual outbreaks of wire worms. Nearly always the invaded home is fairly new, and has no landscaping in either the front or back yards. The bare dirt dries out and heats up, and it may be this combination that drives these larvae out of the soil to seek a cooler and moister place to live. Their legs are very short, but long enough to allow them to make it to the base of the house, and from there perhaps under doors or into wall voids. As they wander they are found on carpeting, attempting to burrow down into the fibers as a way of hiding themselves. They are not going to do any actual damage, and the invasion is only a nuisance, but to many people it can be intolerable. The best control for these insects, when found indoors, is to remove them with a vacuum cleaner. Pesticide applications are not justified.
To resolve the problem outdoors, and to keep them from continuing to emerge from the soil, I generally recommend watering down the dirt, even though nothing may be growing there. By cooling off the hot, dry soil it may be the stimulus needed to return that subterranean environment to one that the larvae can withstand, and once the hot spell is over the problem seems to go away as well.
There are some interesting species in this family, and we’ll discuss just a few of them. One mentioned earlier is a species that produces light, and it fittingly is in the group of click beetles with the Latin name Pyrophorus. There are a few species of this group in the southern United States, and others south of that in Latin America. They are relatively large, with the adult beetle reaching about 1 inch in length in the U.S., and tropical species double that in size. They produce light in two yellow spots on the top of their thorax, and when they are flying through the air they look for all the world like a bright orange spark. Their light is not the famous blinking of fireflies, but more of a steady glow, and on a very dark night it is an impressive sight. Except for these two light spots the beetles are otherwise solid dark brown over their entire body. For more of a discussion on insects that produce light see another BugInfo article on “Fireflies and Lightning Beetles”.
Another striking group of click beetles are the “eyed elaters”, in the genus Alaus. These can be very large species, up to 2 inches or more in length, and on the top of their thorax they have two very large, very noticeable spots that look exactly like large eyes. The real eyes, of course, are much smaller and are located on either side of the head, but it is thought that these fake eyes must serve the insect a purpose in its quest to survive the many dangers of living life as a beetle that cannot sting or bite. A great many other insects also have eyespots on them, perhaps those on butterflies and moths the most developed. You may have seen pictures of “Owl Butterflies”, whose eyespots on the underside of their hindwing give them the striking appearance of an owl looking back at you. It could be that a potential predator – perhaps a bird – would see these prominent eyespots and believe the animal to be much larger than it really is, preferring to leave it alone rather than take a chance by biting into it.
In the tropical parts of the world, as it seems always to happen, insect life goes wild, and the sizes, shapes, and colors become outrageous. Click beetles have taken part in this amazing diversity too, and we find large species there that are like chunks of shiny metal, with their entire body a brilliant metallic greenish or blue color. Just how this brilliance benefits the insect is difficult to say, but since these species have survived the hazards of life for many hundreds of thousands of years it must work for them. So, the next time you hear that mysterious clicking, and the cat seems to be fascinated by something on the kitchen floor, take a close look and appreciate these interesting beetles.