Agriotes sputator (Linnaeus, 1758)

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POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

ELATERIDAE Leach, 1815

ELATERINAE Leach, 1815

AGRIOTINI Laporte, 1840

Agriotes Eschscholtz, 1829

Generally common and often abundant throughout Europe except for the far north, this species extends east through Asia Minor and Kazakhstan to the far east of Russia and south to North Africa, and since the early 20th century it has also become established  in eastern Canada and the United States where it is sometimes very abundant among arable crops. In the UK it is generally common across southern England and the midlands, mostly coastal in the West Country and Wales and very local and scarce further north to the Scottish borders, it occasionally occurs in large numbers and may be a pest of various crops but it does not achieve the notorious pest status seen on the continent and through Asia where it is among the most harmful pests of a very wide range of crops but especially cereals, sunflower, potato and beet, it also attacks saplings and amenity grass and, to a lesser degree, legumes; larvae attack the roots, stunting growth and destroying seedlings, and also feed directly on seeds as soon as they are sown and so heavy infestations, which are common, can seriously reduce crop development and yields. Adults are active from March or April when the soil temperature reaches 10°C, they become active in the afternoon and disperse by flight in the evening when they feed on tender foliage and visit flowers and blossom. Mating and oviposition begin soon afterwards and continues for about two months but by June most adults have died off. Females lay eggs in small groups between 5 and 10cm below the soil surface, generally near the base of suitable host plants and usually where it is damp as lack of moisture will slow their development and eventually kill them off, and each will lay more than one hundred eggs over the season. Larvae emerge after about three weeks and begin feeding immediately on roots, they mostly remain near the surface but this is dictated by the moisture content of the soil as they can survive long periods without food but soon die without moisture, they are very active and move readily between host plants or through the soil to avoid adverse conditions, Larval development takes between two and four years depending on food and temperature etc., they move deeper into the soil in the autumn to overwinter and move up when the temperature increases in the spring, they begin feeding when the soil reaches 12°C and will not normally feed below this temperature, at near freezing temperatures they become cataleptic and at -4°C they die within a few hours. Pupation occurs deep in the soil during July and August and adults are fully formed within two or three weeks but they remain in the soil until the following spring. Adults may be swept from grass and herbaceous foliage in most situations and they are sometimes common on umbel flowers in bright sun, they are often abundant in grassland on open sandy or chalky soils but are generally common in most fairly dry situations including woodland, gardens, dunes and road verges etc.

Agriotes sputator 1

Agriotes sputator 1

Agriotes sputator 2

Agriotes sputator 2

Agriotes sputator 3

Agriotes sputator 3

Agriotes sputator 4

Agriotes sputator 4

Agriotes sputator 5

Agriotes sputator 5

5.5-8.0 mm. Very typical of the family, this species will soon become familiar dark colouration and broadly-oval form, head dark grey, pronotum dark grey with variable paler brown borders, elytra a mixture of dark grey and brown, typically dark with the suture and lateral margins paler but unicolourous dark and pale forms are common, appendages dark to pale grey or brown, usually with the antennae paler. Head smoothly convex with small, weakly convex eyes that usually touch the pronotal margin, finely punctured and pubescent throughout, the pubescence directed obliquely forward away from the centre, antennae 11-segmented; the second segment about as long as the fourth. Pronotum quadrate to slightly elongate, broadest about or in front of the middle and rather strongly curved to a narrow anterior margin and straight or only very weakly sinuate to backwardly-produced posterior angles, surface evenly convex, without a lateral ridge at the posterior angles, and finely punctured and pubescent. Elytra with rounded shoulders and evenly curved to an acuminate apex, with well-impressed and punctured striae complete to the apex and finely punctured and rather densely pubescent interstices. Legs long and slender; femora only narrowly visible in normal setting, tibiae straight and almost equal in length, each with a fine but distinct apical spur. Tarsi 5-segmented, all segments distinct and segments 2-4 almost equal in length, variously lobed ventrally but not widely so. Claws smooth and without a distinct basal tooth.