click beetle

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Click beetles
Click beetle adults and larvae (wireworms) Left: Wheat Wireworm (Agriotes mancus) Right: Sand Wireworm (Horistonotus uhlerii)
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Class: Insecta Order: Coleoptera Superfamily: Elateroidea Family: Elateridae Leach, 1815
Subfamilies
Agrypninae Anischiinae Aplastinae Cardiophorinae Cebrioninae Latreille, 1802 Dendrometrinae Denticollinae Dicronychinae Elaterinae Hypnoidinae Lissominae Melanotinae Negastriinae Prosterninae Subprotelaterinae Thylacosterninae
Synonyms
Campylidae Cavicoxumidae Ludiidae Monocrepidiidae Pangauridae Phyllophoridae

The family Elateridae is commonly called click beetles (or "typical click beetles" to distinguish them form the related Cerophytidae and Eucnemidae), elaters, snapping beetles, spring beetles or "skipjacks". They are a cosmopolitan beetle family characterized by the unusual click mechanism they possess. There are a few closely-related families in which a few members have the same mechanism, but all elaterids can click. A spine on the prosternum can be snapped into a corresponding notch on the mesosternum, producing a violent "click" which can bounce the beetle into the air. Clicking is mainly used to avoid predation, although it is also useful when the beetle is on its back and needs to right itself. There are about 9300 known species worldwide^[1] and 965 valid species in North America^[2].

Description and ecology

Adelocera murina on its back, with the click mechanism visible

Click beetles can be large and colorful (e.g. Selatosomus cruciatus), but most are small to medium-sized (<2 cm) and dull. The adults are typically nocturnal and phytophagous, but rarely of economic importance. In hot weather, they may enter people's houses at night if entries or windows are left opened but are not a pest. Click beetle larvae, called wireworms, are usually saprophagous, but some species are serious agricultural pests, and other species are predators of other insect larvae. A few elaterid species are bioluminescent (in both larvae and adult forms), such as Pyrophorus.

Larvae are slender, elongate, cylindrical or somewhat flattened, and relatively hard-shelled for larvae--bearing resemblance to common mealworms (Tenebrionid larvae; e.g. Tenebrio molitor). The three pairs of legs on the thoracic segments are short and the last abdominal segment is, as is frequently the case in beetle larvae, directed downwards and may serve as a terminal proleg in some species. The posterior end of the body (9th abdominal segment) is pointed in larvae of Agriotes, Dalopius, and Melanotus, but is bifid due to a so-called caudal notch in Selatosomus (formerly Ctenicera), Limonius, Hypnoides, and Athous species^[3]. The dorsum of the 9th abdominal segment may also have sharp processes (e.g. in Oestodini such as Drapetes spp. and Oestodes spp.). Although some species complete their development in one year (e.g. Conoderus), wireworms usually spend three or four years in the soil, feeding on decaying vegetation and the roots of plants, and often causing damage to agricultural crops such as potato, strawberry, corn and wheat^[4][5]. The subterranean habits of wireworms, their ability to quickly locate food by following carbon dioxide gradients produced by plant material in the soil ^[6], and their remarkable ability to recover from illness induced by insecticide exposure (sometimes after many months)^[7], make it hard to exterminate them once they have begun to attack a crop. Wireworms can pass easily through the soil on account of their shape and their propensity for following pre-existing burrows^[8], and can travel from plant to plant, thus injuring the roots of multiple plants within a short time.

Other subterranean creatures such as the leather-jacket grub of crane flies which have no legs, and geophilid centipedes, which may have over two hundred, are sometimes confounded with the six-legged wireworms.

Larvae of some Brazilian savanna species of click beetles live in burrows scattered over the surfaces of termite mounds using their bioluminescence to attract flying prey.^[9]

Selected genera

Eyed click beetle Alaus oculatus

References

This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.

External links

Wikimedia Commons has media related to: Elateridae

Wikispecies has information related to: Elateridae

• click beetles, Alaus spp. on the UF / IFAS Featured Creatures Web site
• Taiwanese Site Images Binomial names
• Limonius wireworm research site