Denticollis linearis (Linnaeus, 1758)
POLYPHAGA Emery, 1886
ELATEROIDEA Leach, 1815
DENTICOLLINAE Stein & Weise, 1877
DENTICOLLINI Stein & Weise, 1877
Denticollis Piller & Mitterpacher, 1783
This species, our only U.K. member of the genus, occurs throughout Europe to the north of Scandinavia, The Near East and Asia; on the continent it is either rare or very rare over many parts of its range. In the U.K. it is generally common throughout England and Wales and there are records scattered through Scotland although sparsely so in the far north. It occurs in a wide range of habitats including broadleaved, mixed and conifer woodland, grassland, parkland and coastal situations with suitable host plants. Adults occur from May to July or a little later depending upon the season and are easily recorded by sweeping low vegetation, grass and shrubs. In the summer they disperse and may be found far from suitable habitats, occasionally being attracted to light. The larvae are omnivorous, feeding beneath bark on insect larvae as well as live wood. In moorland habitats they also develop in peat or moss. The larvae overwinter and pupation occurs in the spring.
Among the U.K. fauna this species is recognizable by the very prominent eyes and the overall form. The colour is very variable and several forms have been named e.g. f. mesomelas Linnaeus, 1758 has been applied to a form in which the elytra are black with pale margins. 9-13mm. Head and femora mostly dark, often black. Pronotum orange to red or brown, and sometimes darkened on the disc. Elytra from black to dark brown or pale yellow but usually with the lateral margins pale. According to Joy the male is entirely yellow but for the head and thorax reddish, the female with black, pale margined elytra and the vertex of the head black. Upper surface with fine yellow pubescence. Head densely punctured, transverse with the clypeus raised in front of very prominent eyes. Antennae 11-segmented and inserted on the side margin in front of the eyes. Pronotum quadrate and convex, with wide, shallow punctures, a median longitudinal impression and a transverse impression in front of the basal margin. Lateral margins sinuate, and hind angles produced and acute. Scutellum large and prominent. Elytra almost parallel or, in the female, dilated behind the middle; with well-impressed rows of large punctures, the interstices finely punctured and cross rugose. Lateral margins weakly sinuate and narrowly explanate. Legs slender; tibiae straight and without obvious spurs. Tarsi 5-5-5, without lobed segments. Claws simple.
DENTICOLLIS Piller & Mitterpacher, 1783
This small genus has a Holarctic distribution; about 40 species are described and the greatest diversity is in Asia where some species are restricted to particular regions e.g. Japan. There are 4 Nearctic species of which 2 are known from North America; D. denticornis (Kirby, 1837) is a widespread Nearctic species, while D. varians (Germar, 184) also occurs in Northern Asia. The European fauna includes 4 species. They are unusual for elaterids in that they superficially resemble certain lampyrids or cantharids. Adults are medium sized beetles, 8-15mm, and of a very characteristic appearance; rather flattened and parallel-sided or nearly so and with very convex and prominent eyes in front of short and curved or parallel temples. The front of the head is margined and the antennae are inserted on the anterior margin in front of the eyes. The appendages are long and the elytra continuously rounded and covering the abdomen. The pronotum is generally quadrate and narrowed anteriorly and in most cases with transverse impressions near the base. Scutellum generally large and prominent. The elytra have strongly punctured striae and narrowly explanate lateral margins and are usually more dilated towards the apex in the female. Most are rather drab coloured insects; various shades of brown or orange but several are very dark or black and strongly metallic e.g. the Asian D. erebus Gurjeva, 1987, while the Nearctic D. denticornis has attractive yellow streaks to the pronotum and elytra. Some species show sexual dimorphism in colour but this is usually variable. In several species the antennae are to some extent pectinate in the male, perhaps best developed in D. flabellatus (Reitter, 1906). The prosternum is rounded anteriorly and the metasternum is narrowed so that the meso-coxae are almost touching. The tarsi are 5-5-5 with the segments either lacking lobes or with the fourth segment weakly lobed. The claws are smooth and lack teeth. The combination of a pointed anterior part to the metasternum and a raised anterior margin to the head will distinguish the genus from other elaterids. Most species are to some extent saproxylic but in general they occur in a wide range of habitats.