Larvae of the click beetles are commonly known as wireworms, primarily because of their hardened exoskeleton and elongate body. Larvae of the brown click beetle, Limonius canus , are especially common in the Pacific Northwest. Like all beetles, wireworms/click beetles go through complete metamorphosis with egg, larva, pupa and adult stages.
Click beetles range in size from very small to large, and are commonly rather elongate. Click beetles are generally drably colored. Most found here are tan brown to black and fairly small, about 12 mm long,. The most interesting feature for members of this family is their ability to "click". The clicking mechanism occurs on the underside and is composed of a spine that extends to the rear and fits into a groove in the midbody. With this mechanism the click beetles can flip themselves in the air, often with an audible "clicking" sound; it helps them to turn themselves over when they are on their backs, and probably is of use in avoiding predators.
A wireworm larva has three pairs of short legs near its head, a pale yellow to reddish brown body, a brown, flattened head, and a scalloped last abdominal segment. When fully grown, this wireworm ranges from 8 to 12 mm in length.
The white, soft-bodied pupa has no protective covering and is approximately the same size and shape as the adult. The larva and pupa live underground.
The wireworm feeds on the roots of many grasses, including corn and many small grain crops. It may also attack the roots, seeds, and tubers of many flower and vegetable crops, especially onions, corn, beans, peas, carrots, potatoes and sweet potatoes (which creates holes in potato and sweet potato roots). They also feed on seedlings.
This wireworm species has a 2-5 year life cycle. In June of the first year, adults deposit eggs singly among the roots of grasses. First instar larvae emerge in July and begin feeding on roots. Larvae continue to develop throughout the summer and over winter in the ground as second instars during the first year. In late July or August mature larvae construct oval cells 15 to 30 cm deep in the soil and pupate. Adults emerge about 18 days later and feed on pollen before hibernating in protected areas. They become active and deposit eggs the following May or June. Adults occur on foliage, or logs and stumps. Many are also attracted to lights at night. Wireworms have few natural enemies.