Laccobius bipunctatus (Fabricius, 1775)
POLYPHAGA Emery, 1886
HYDROPHILOIDEA Latreille, 1802
HYDROPHILINAE Latreille, 1802
Laccobius Erichson, 1837
Widespread and generally common throughout most of the Palaearctic region from Europe and North Africa to Siberia, although it probably extends further east as it was only recently recorded from China (Jia, 2013). In Europe, it is often the most frequently recorded member of the genus, it occurs generally but is probably more common in cooler central and northern areas where it reaches the UK and the Baltic countries; extending into southern Norway and Finland, and central Sweden. To the south it avoids warm water habitats and is often most frequent at higher altitudes. The species is common and often abundant throughout the UK, including all the islands, though less so in the north of Scotland and across Ireland. The usual habitats are small ponds, ditches, peat bogs and shallow margins of other still water bodies, usually with dense aquatic and marginal vegetation; although during the summer the adults often occur among matted or filamentous algae in very shallow water. Adults are present year-round; they are active from March until October, and peak in abundance during May and September. At least a proportion of adults are able to fly and they sometimes appear at light traps during the summer. Little is known of the biology but larvae are predaceous while adults are herbivores or scavengers. The early stages have not been described, but a Japanese species has been described in fine detail by Minoshima et.al (2017) The most common of our UK species and easily found by working through samples of vegetation or marginal substrate in a tray, although they are easily seen in the water net, and they usually occur in numbers.
3.0-3.5 mm. Broadly-oval and strongly convex; forebody rather dull due to distinct (x40) microsculpture, elytra lacking microsculpture so more shiny, ventral surface flat and densely pubescent. Head broadest across the base and smoothly rounded anteriorly, extensively dark but for a variable pale spot in front of the eyes. Vertex and frons evenly convex and finely punctured, eyes large and continuous with the outline. Palps about as long as antennae, pale but for the base and the extreme tip which are darkened. Antennae 8-segmented; pale with darker 4-segmented clubs. Mentum flat and punctured, not rugose. Pronotum transverse, broadest across rounded posterior angles and narrowed to slightly projecting anterior angles, basal margin simple and almost straight, apical margin curved. Pronotal surface extensively finely punctured and microsculpture, pale with an irregular large and dark (slightly metallic in some lights) discal mark which extends to the basal margin. Elytra smoothly curved from rounded shoulders to a continuous apical margin, pale with numerous rows of dark spots which vary in size, in some specimens the elytra being substantially dark, striae irregular and comprising two sizes of punctures, interstices without microsculpture. Tibiae with paired apical spurs. Tarsi 5-4-4; second and third segments of front tarsi dilated in males, all segments otherwise simple.
Laccobius bipunctatus 1
Laccobius bipunctatus 2