Haliplus lineatocollis (Marsham, 1802)

Considered by Balfour-Browne (Vol1, p28) as, with the possible exception of H.ruficollis, our most common haliplid, this species occurs throughout the UK including Scilly, Lundy, IOW, Man, Anglesea, the Western Isles and Orkney and there is a single (Pre 1979) record from Shetland (NBN). This species occurs in a wide variety of habitats including stagnant or running fres, peaty or brackish water at both low and high elevations (Balfour-Browne). Holman (1987) gives 'mainly in base rich ponds and streams'. Locally as with Gyrinus substriatus, H.lineatocollis is of curious occurence; from our general observations dating back to the early 1980's we know the species to have been common and usually abundant throughout our area as well as further south along the Colne valley through Rickmansworth, Uxbridge and Cowley. We have recorded them from the margins of gravel pits, canal and river margins and ponds throughout the year. Through the winter they have often been common, along with other haliplids, on the underside of floating debris over shallow water. And so it is surprising that since our recording for this site began in 2006 we have found only a single specimen, extracted from a sample of pondside vegetation from below Cassiobury park on 10/8/08. Along with several other sites this pond is visited regularly and contains a large population of H.ruficollis. The search goes on but it is curious that a species so abundant and widespread locally only a few years ago should now be very scarce.

Oviposition occurs in the spring or summer and larvae appear soon afterwards, larvae may be found throughout the year (Bertram in Balfour-Browne) and in southern Europe the life cycle may be completed in the same year whereas further north the larvae usually hibernate out of water and pupat the following spring to produce adults within a few weeks.

An elongate and somewhat parallel sided species. Without experience most haliplids need to be examined very carefully but most specimens of lineatocollis will be obvious due to the dark pronotal line, a character unique to this species.

2.6-3.5mm (Friday,1987). Colour varies but upperside usually dark yellow, head (usually) and longitudinal median mark om pronotum dark, elytra with darker markings, ill defined but may be extensive. Appendages testaceous. Upper surface glabrous, without setae. Head smooth and shining, densely punctured, more sparsely to behind eyes which are very convex and occupy most of the side of the head. Pronotum broadest at base, narrowing to weakly protruding front angles. Hind margin strongly sinuate, produced back to elytral suture. Lateral margins bordered. Punctured anteriorly as strong as head, sparsely so or completely smooth towards hind margin. With a long inwardly curved furrow either side from base to about half way , a character unique to the species. Scutellum not visible. Upper surface of elytra rather flattened, punctured striae well developed to apex, at base some of these form raised ridges. Interstices flat and shiny, with small punctures, much smaller than those of striae, which sometimes form lines. All tibiae with a pair of strong apical spines on inner side. Tarsi 5-5-5, last segment notably elongate, male pro and mesotarsi with segments 1-3 slightly dilated. Claws simple, slender but prominent, claws of all pairs more or less equal.

Some other species have smaller furrows, no more than 1/3 pronotal length.