Haliplus ruficollis (De Geer, 1774)

Common and usually abundant throughout England, Wales and Scotland north to Stirling and Kinross, further north records are more scattered, there are none from much of Aberdeen, Moray and north of Easter Ross. There are records from the Isles of Wight, Scilly, Anglesey, Man, Orkney and the Western Isles but not Shetland. They occur throughout our Watford area, usually in still and stagnant water and usually in large numbers. Adults may be found in water year round; during the winter by removing and examining floating or submerged debris, from early spring by sweeping among aquatic vegetation and during the summer in large numbers by sweeping generally. We once (July, 08) found large numbers among a sample of duckweed from Cassiobury park taken for extraction. Holmen (1987) states that 'hibernation of larvae and adults normally takes place out of water' but we have yet to see this locally, through the winters of 2005-8 we have extracted many samples of debris and vegetation from pond margins etc without success. More generally they are a typical species of smaller water bodies rich in vegetation but may also occur in streams, lakes and brackish water eg through the 1970's and 1980's they were common around the margins of gravel pits near Uxbridge (Middx).

Eggs are laid inside cells of submerged plants throughout the summer and larvae appear within a few weeks, some of these may pupate in the autumn but generally they overwinter to pupate the following spring. The pupal stage lasts for a few weeks and this generation of adults will probably reproduce the following year. Both larvae and adults feed mainly on filamentous algae and the species is thought to be to some extent tolerant to pollution. Adults are known to fly but we have not recorded them at MV despite running lights near to water known to contain large populations of the beetle.

2.5-3.0mm. Elongate broad oval with elytra widest before middle and pointed at apex. Ground colour generally from pale to dark orange but almost yellow or red specimens occur. Head shiny, with sparse puncturation distinct at X20. Eyes large, convex and protruding. Antennae and palps entirely pale testaceous. Base of head usually darker. Pronotum widest at base and narrowed to front margin, lateral margin straight and distinctly bordered. Hind margin strongly sinuate and produced medially so that the scutellum is not visible. Entirely yellow to red, the front margin is often darker due to the underlying dark cuticle of the head. Surface puncturation a little stronger than that on the head, mostly sparse but may be dense behind front margin. Basal striae (opposite the fourth elytral striae) short, around 1/5 pronotal length, and curved inwards. Elytra with rows of large punctures, each with an underlying black mark, these marks are often confluent so forming distinct black striae which vary in width and may coalesce laterally to form large dark marks, generally one near the centre of each elytron and two or three laterally. Some specimens are pale with discreet rows of black marks, others are extensively darkened, especially behind middle. Often with scattered smaller punctures which may form a line on inner interstices.

In the female the basal third or half of the elytra is shallowly and quite densely punctured, this is first visible at X40, in the male this area is smooth. The claws of each pair are equal in the female, the male protarsal claws are unequal; the inner claw is shorter, broader and more curved. In the male the basal mesotarsal segment is distinctly sinuate on the inner surface, in the female it is straight.

There are a couple of good keys that cover the British species of Haliplus, those by Friday and Holmen (1987) will be found to be essential. The following advice is written from the viewpoint of an amateur without experience of most of the British Haliplus and reflects some of the problems experienced.

H.ruficollis is easily separated from some other groups of the genus:
In our three species of the subgenus Haliplus Lat. (H.confinis St., H.obliquus (Fab) and H.varius Nicolai) the upper surface is almost entirely and rather densely punctured, this is obvious at X20.
Our five species of Liaphlus Guignot lack the impressed striae at the base of the pronotum.
This leaves eight species of the subgenus Haliplinus Guignot. These are keyed on morphological characters by Holmen and partly so by Friday, and it is very tempting to rely on these when first starting to identify Haliplus species. We now illustrate the problems associated with this by discussing our own attempt to identify a sample of about fifty specimens taken from across our area. Using Friday's key the specimens were first grouped into males and females according to whether the basal mesotarsomere is dilated or not. As advised the females were ignored. The unequal protarsal claws narrowed the search down to H.immaculatus, H.ruficollis and H.wehnckei. From here they were separated into two groups; immaculatus, which seemed obvious, and ruficollis/wehnckei according to the degree of sinuation and widening of the basal mesotarsomere. Friday gives some advice on the depth of the concavity formed by this sinuation when compared to the diameter of the tibial spur and this seems helpful when assigning males.
Holmen gives a detailed key to these species, and our group of male specimens goes straight to immaculatus where he gives the additional character of a longitudinal keel on the ventral side of the mesotarsomeres which is no doubt useful but to us, without experience and with our rather basic stereoscopes it did not help. From here there are a few couplets that eliminate species mostly on tarsal characters until we come to ruficollis. Our original separations were looking shaky and we soon came to the coclusion that either some experience was needed which we lacked, or that examples of other species for comparison would have been useful. It should be said that details of the shape and typical pattern of the elytra are given in both works but these did not help for us, we simply had lots of material that might have been one three species. For us at least, so much for external morphology.
Both works give good drawings of the genitalia and these, it is immediately obvious, are highly diagnostic - Friday stresses the point and it is implicit throughout Holmen's work. In our three possible species the male genitalia are very different and cannot be confused for each other. There are three parts; two parameres and the penis. The penis and one of the parameres (called the left in Friday and the right in Holmen but it does not matter as they are obvious) are absolutely distinct and for ruficollis they look like this:



If the genitalia looks like this then the specimen is ruficollis, the morphologically close species have very different male genitalia. All our specimens turned out to be ruficollis - even those we were sure were immaculatus Experience may have allowed an identification on morphology alone but without this we would say that dissection is essential. This was written after dissecting twenty male specimens and we were careful to examine the basal mesotarsomere for sinuation, some of these would have been left as immaculatus and the rest as ruficollis/wehnckei. Friday states 'rely on identification of males and refer to the table at the end of the key for details of the male genitalia'. Fair enough. Females can be identified by companion or association, Holmen gives line drawings of the female genital sclerites and we have compared some dissected material with these figures, again we think that experience or some comparative material is needed here.

Two species, H.wehnckei and H.sibiricus are keyed in Holmen which are now synonymised. (Lundmark, Drotz and Nilsson, 2001)

Holmen, 1987 The aquatic adephaga of Fennoscandia and Denmark. Fauna Scanda Vol 20
Lundmark, M, Drotz, M.K. and Nilsson, A.N 2001. Morphometric and genetic analysis shows that H.wehnckei is a junior synonym of H.sibiricus. Insect systematics and evolution 32:241-251