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The eyed click beetle is found in the
southern
U.S. as far west as Texas. At up to 2 inches long, it is one of
the largest known "click" beetles in the family Elateridae. The
huge false eyespots make it readily identifiable; it is thought
these startle predators into thinking they are confronting an
animal much larger than it really is. The true eyes are located
behind the base of the saw-toothed antennae. Most click beetles
are considerably smaller and not as conspicuously marked.
All click beetles have a defense mechanism
responsible for their common name; when disturbed, the beetle
launches itself high into the air with an audible click. This
feat of strength is accomplished through the use of a stiff
chitinous spine on the underside of the prosternum that fits
into a groove on the mesosternum; the beetle build pressure
against the spine which is suddenly released causing the two
segments to spring violently apart. It is said the beetle is
able to transition into winged flight during these excursions,
but we have never witnessed this phenomenon, and knowing the
machinations beetles must undergo to get their flying wings
activated, we find it highly unlikely. Indeed, we think the
rapid escape mechanism evolved at least in part to compensate
for the slow response of the flying equipment. (See figure 2.)
Awesome!
Click beetles undergo complete metamorphosis:
Egg - larvae (beetle larvae are called "grubs") - pupa - adult.
Some species of click beetle have larvae that have a hard shell,
commonly called "wireworms." These grubs can be serious
agricultural pests, feeding as the do on the roots of plants
(corn and other cereal grains are often attacked) during their
1-3 year portion of the life cycle. Wireworm larvae are hard,
smooth, slender, wire-like worms varying from 2 to 1 inches in
length when mature. They are a yellowish-white to a coppery
color with three pairs of small, thin legs behind the head. The
last body segment is forked or notched
Life History
Wireworms usually take three to four years to develop from the
egg to an adult beetle. Most of this time is spent as a larva.
Generations overlap, so larvae of all ages may be in the soil at
the same time. Wireworm larvae and adults overwinter at least 9
to 24 inches deep in the soil. When soil temperatures reach 50
to 55 degrees Fahrenheit during the spring, larvae and adults
move nearer the soil surface. Adult females emerge from the
soil, attract males to mate, then burrow back into the soil to
lay eggs. Females can re-emerge and move to other sites where
they burrow in and lay more eggs. This behavior results in
spotty infestations throughout a field. Some wireworms prefer
loose, light and well drained soils; others prefer low spots in
fields where higher moisture and heavier clay soils are present.
Larvae move up and down in the soil profile in response to
temperature and moisture. After soil temperatures warm to 50 F,
larvae feed within 6 inches of the soil surface. When soil
temperatures become too hot (>80 F) or dry, larvae will move
deeper into the soil to seek more favorable conditions.
Wireworms inflict most of their damage in the early spring when
they are near the soil surface. During the summer months the
larvae move deeper into the soil. Later as soils cool, larvae
may resume feeding nearer the surface, but the amount of injury
varies with the crop.
Wireworms pupate and the adult stage is spent within cells in
the soil during the summer or fall of their final year. The
adults remain in the soil until the following spring.
Damage
Wireworm infestations are more likely to develop where grasses,
including grain crops, are growing. Crops susceptible to injury
include small grains, corn, potatoes, sugar beets and
vegetables. Legumes are less likely to be injured. Wireworms
damage crops by feeding on the germinating seed or the young
seedling. Damaged plants soon wilt and die, resulting in thin
stands. In a heavy infestation bare spots may appear in the
field and reseeding is necessary.
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