Agriotes sordidus (Illiger, 1807)

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POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

ELATERIDAE Leach, 1815

ELATERINAE Leach, 1815

AGRIOTINI Laporte, 1840

Agriotes Eschscholtz, 1829

With the exception of warmer southern parts of the range this is a generally local and uncommon species, it has a mostly western and southern European distribution, occurring from Portugal to the UK, Belgium and Germany in the north and to Italy and Ukraine in the south; it occurs in Greece but is generally absent from the Balkan Peninsula, and is present on many Mediterranean islands as well as the Canaries and western parts of North Africa. In the UK it is very local and scarce and most records are coastal, from Essex to South Devon and along the south coast of Wales, and there are a small number from the midlands (possibly based on misidentifications.) Across Europe it is typical of damp forests and steppe grassland as well as riparian and coastal habitats but in the UK typical habitats include densely-vegetated saltmarshes and tidal river margins. Adults are active from April until July or August, usually occurring in numbers, they are diurnal and may be swept from vegetation but they fly well and visit a range of flowers including various umbels, mating occurs after a period of feeding on foliage and continues through the season. Females oviposit through the season; they lay small batches of eggs into the surface of damp soil among roots and litter and larvae emerge after a week or two. Larval development is slow and depends on temperature and food supply, they need to feed soon after hatching and most will die within a about five weeks if they fail to do so, hence the oviposition site is important, they develop through between eight and thirteen instars and each becomes more resistant to starvation, the final instar being able to survive up to a year without food, they are widely polyphagous but the rate of development does not depend on the type of food, rather soil temperature and moisture content. Larvae feed on roots during the warmer months and move deeper into the soil to overwinter, each instar taking longer to develop than the previous one and involving three distinct phases, head and mandible hardening, feeding and growth, and a pre-moulting phase. Final instar larvae move deeper into the soil to pupate in an earthen cell from late May until July, this final stage lasting between two and three weeks depending on temperature. In northern latitudes the life-cycle takes about thirty-six months and is spread over four years but in Mediterranean areas, where large populations sometimes become serious crop pests and pheromone traps are used to control them, it takes about twenty-four months spread over three years.

Agriotes sordidus

Agriotes sordidus

8-9 mm. Recognized to the generic level by the smooth claws and the second antennal segment being as long as the fourth, as such it might only be confused with other members of the genus, notably A. sputator (Linnaeus, 1758). Elongate and discontinuous in outline, entirely dark grey to mid-brown entire upper surface with rather dense short pale pubescence which tends to become rubbed in the field, legs pale to dark brown, often with the femora darker, antennal pale, usually with the basal segment to some extent darkened. Head only narrowly visible from above, the weakly convex eyes usually partly obscured by the pronotal margin, surface finely and densely punctured throughout. Pronotum quadrate, broadest about the middle and evenly narrowed to  obscure anterior angles, lateral margins almost straight and parallel in the basal half, posterior angles produced and with a short keel inside the margin, surface rather dull, finely and densely punctured throughout. Elytra with rounded shoulders evenly curved to a continuous apical margin, broadest about the middle, this varies but is usually at least as broad as the pronotum, striae narrow and finely punctured to the apex, interstices about equal in width throughout, finely punctured and pubescent. Legs long and slender, tarsi 5-segmented, without bilobed segments, claws smooth.

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Agriotes sordidus