Dalopius marginatus (Linnaeus, 1758)

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POLYPHAGA Emery, 1886

ELATEROIDEA Leach, 1815

ELATERIDAE Leach, 1815

ELATERINAE Leach, 1815

AGRIOTINI Laporte, 1840

Dalopius Eschscholtz, 1829

This generally common and often abundant species occurs throughout Europe north to the UK and above the Arctic Circle in Scandinavia, it extends east through Russia and Asia Minor to northern Kazakhstan and Mongolia and is present fro, lowlands to the upper limit of the tree line in mountain areas. It is common throughout mainland UK and Northern Ireland and occurs on most of the islands north to Orkney, typical habitats include grassland and low vegetation in open wooded areas, parkland and along hedgerows, they are often common on disturbed ground but are rarely found in domestic gardens, on the continent it is often more associated with woodland and in the north, where very large populations can occur in pine forests, it is sometimes considered as a pest as larvae may kill or retard the growth of seedlings. Adults occur from May until July, they are active in warm weather and the earliest specimens occur on hawthorn blossom and umbel flowers but they are soon common and may be swept from low vegetation and shrubs. Mating occurs after a period of feeding and females lay eggs into the ground where the larvae will develop, feeding on tender roots as well as other insect larvae. Larvae live mostly near the surface of the soil, between 1 and 5 cm deep, but move deeper to overwinter or to pupate; the life-cycle takes between 3 and 4 years depending on temperature and nutrition and fully-grown larvae pupate in a subterranean cell from early summer. Adults are fully-formed from August but they remain within the remains of the pupa and overwinter to emerge in May as the temperature rises. They may be sampled through the season by sweeping vegetation of beating flowers into a net, they superficially resemble several other species but the size and bicoloured elytra soon become distinctive in the field, and unlike some other species e.g. Agriotes acuminatus (Stephens, 1830) or A. pallidulus (Illiger, 1807) they tend to occur in small numbers.

Dalopius marginatus 1

Dalopius marginatus 1

Dalopius marginatus 2

Dalopius marginatus 2

Dalopius marginatus 3

Dalopius marginatus 3

6.0-7.5 mm. Elongate and rather parallel-sided with a broad head and sinuate pronotum, upper surface rather shiny and finely pubescent throughout. Head black to dark brown, pronotum dark with variable pale brown margins, elytra pale brown with the base and sutural area variably darker, very rarely the pronotum and elytra are almost completely dark, legs pale brown, antennae darker brown or pale with the central segments darker. Head broadest across large convex eyes, very nearly as broad as the anterior margin of the pronotum, evenly convex and densely and quite strongly punctured throughout. Antennae filiform with all segments elongate; the basal segment as long as the next two combined and the second much shorter than the fourth. Pronotum quadrate and smoothly sinuate laterally to rather strongly produced posterior angles, surface smoothly convex and finely and quite densely punctured throughout, without a ridge inside the posterior angles, in side view the lateral bead appearing straight from the posterior angle to the anterior margin. Elytra pale, usually darkened across the base but not including the shoulders and along the first two or three interstices almost to the base, all striae well-impressed and punctured from near the base to the apex, interstices finely and randomly punctured and rugose throughout. Tarsi 5-segmented; the fourth segment of the middle and hind tarsi distinct and a little longer than half the length of the third segment. Claws smooth and without a distinct basal tooth.