Agriotes lineatus (L.) - Common Click Beetle, Click Beetle, Striped Elaterid Beetle (GB), Lined Click Beetle (Wireworm) (US).
Taxonomic position.Class Insecta, order Coleoptera, family Elateridae, subfamily Elaterinae, genus Agriotes.
Biological group.Polyphagous soil inhabiting pest.
Morphology and biology.Body length 8-11 mm, width 2.6-3.2 mm. Head with rough dense simple and deep punctures. Antennae reaching apex of hind angles of pronotum or protruding behind the latter by half the length of the last antennal segment. Pronotum almost as long as wide or slightly wider than long, covered with dense rough uniform punctures. Body hazel to umber; antennae, tarsi, and odd interrows on elytrae brown-yellow, less often yellow-brownish. Body dorsum and ventrum covered with short yellow-grayish hairs. Larvae reach 27 mm in length, to 2 mm in width, prolate and rigid, light-yellow; the lateral sides of their tergits are darker than central line along middle of dorsum. In their original habitus the larvae are usually called Wireworms. Mandibles bear a small tooth forming an acute angle of 60°. The pest over-winters as adult and larva. Beetles are active from the end of April (south) or from the beginning of May (central part of area) until the end of June; mass flying occurs during the second half of May or (in northlands) in June. The period of adult activity lasts 1-2 months. Fecundity is 75-135 with 200 as a maximum. Eggs develop for 14-30 days depending on soil temperature. Depending on temperature and humidity, the larval development lasts 2 to 4 years. Pupation occurs in July and August; pupae develop for 2-3 weeks. The entire developmental cycle of a generation lasts 4 to 5 years.
Distribution.The species occurs from western borders of the former USSR to the Pacific coast of Russia (except for tundra and deserts of Middle Asia), including almost the entire European part, north Kazakhstan, Siberia, western Kopetdag (Turkmenistan), the Far East, south Sakhalin. Appears everywhere in Europe (except for the Far North), Asia Minor, north Mongolia. Introduced into Canada, Brazil, Haiti, and New Zealand.
Ecology.Beetles appear when the soil heats to 12-13°C. They lead a concealed mode of life, weakly flying in the evening or immediately after sunset. Flight starts at temperatures no less than 21°C and humidity 80%. Species lays its eggs in small groups in the upper soil layers at wet patches. When moisture is lacking, the eggs fail to develop and die. Foci of the pest mass reproduction are located on herbaceous cereals. Larvae eat seeds, sprouts, young tillers, roots, seeking them by odor. Larvae are capable of surviving without nutrition for a long time, but they die quickly without contact water. Larvae are highly sensitive to drought, and they make permanent movements, searching optimal conditions. They rise to the warmed upper layer of soil in early spring, descending to great depths from the freezing upper layer during late autumn. Larval body is well adapted to movements in the soil, being smooth and firm. Cuneate head serves as digging organ, legs work as locomotor apparatus, and sharp caudal appendage is used for fixation of body position and reverse movements. The species is hygrophilous, ecologically plastic. In forest and forest-steppe it is common in dry- and water-meadows, arable lands, occurring in steppe in water-meadows primarily and in other highly moistened meadows. The pest prefers soils with large amounts of plant tailings and humus (meadow, meadow-peaty soils, and peat bogs), where it can reach exceptionally high numbers, such as 200 and more larvae per sq. m. Reduction of wireworm numbers is caused by birds (rooks, crows, starlings, etc.) during plowing, and by parasitic and predatory insects (especially by ground beetles of the genera Carabus, Calasoma, Harpalus, Amara, etc.), and also due to diseases (bacterioses, fungal infections).
Economic significance.One of the most common harmful agricultural insect pests. Polyphagous, damaging almost all agricultural crops, such as wheat, rye, oats, barley, maize, potato, beet, carrot, onion, alfalfa, clover, tomato, and fruit saplings. It causes the maximum harm by feeding on sown seeds and seedlings, eating nodes of tillering in cereals, and penetrating into roots. Control measures include early treatment of soil (removal of stubble and plowing, cultivation of fallow lands, inter-row treatment of cultivated crops), crop rotation, mineral fertilizing and dung application, weed (especially couch-grass) control, use of less susceptible cultures and varieties sown on fields heavily populated by wireworms, chemical treatment of seeds and application of soil insecticides, arrangement of poison baits on especially valuable fields. Pheromone traps are a prospective means for the purposes of forecasting; plant breeding for resistance to the pest is potentially effective.
Reference citations.Aleinikova M.M. 1962. Experience of ecofaunistic ranking in click beetles at Middle Volga region. Zool. Zhurn. 41 (7): 1028-1040. (in Russian).
Cherepanov A.I. 1957. Click beetles of Western Siberia (Coleoptera, Elateridae). Novosibirsk: Novosibirsk Publishing House, 382 p. (in Russian).
Cherepanov A.I. 1965. Wireworms of Western Siberia. Moscow: Nauka. 191 p. (in Russian).
Dolin V.G. 1964. Larvae of click beetles (wireworms) of the European part of the USSR. Kiev: Urozhai, 207 p. (in Russian).
Dolin V.G. 1988. Click beetles. Cardiophorinae and Elaterinae. In: Fauna of Ukraine. Beetles. V. 19 (4). Kiev: Naukova Dumka, 204 p. (in Russian).
Gur'eva E.L. 1979. Click beetles (Elateridae). Subfamily Elaterinae. In: Fauna of the USSR. V. 12(4). Leningrad: Nauka, 451 p. (in Russian).
Kryzhanovskii O.L., ed. 1974. Insects and mites as pests of agricultural crops. V. 2. Coleoptera. Leningrad.: Nauka, 335 p. (in Russian).
Shchegolev V.N., Znamenskii A.V., Bei-Bienko G.Ya. 1934. Insects harming to field crops. Leningrad & Moscow: OGIZ - Sel'khozgiz, 464 p. (in Russian).