Laccobius minutus (Linnaeus, 1758)
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POLYPHAGA Emery, 1886
HYDROPHILOIDEA Latreille, 1802
HYDROPHILINAE Latreille, 1802
Laccobius Erichson, 1837
This Palaearctic-wide species occurs continuously from Western Europe and Asia Minor to the far east of Russia, and Japan. The species occurs throughout Europe although only sporadically and infrequently so in the south; it seems to be absent from Portugal and there are very few records from Spain, it is present on a few of the Mediterranean islands but absent from North Africa. It is generally common and often abundant from lowlands to lower mountain altitudes in central and northern areas, and extends beyond the Arctic Circle in Fennoscandia. In the UK it is common throughout the mainland, though less so in the west and the north, and with the exception of Shetland, is present on all the islands. The Irish distribution is rather sporadic; it is generally common across the north-west but otherwise very local. The species is widely eurytopic; it prefers well-vegetated and slightly acidic waters, but more generally might occur in any still or slow moving water, including brackish pools in coastal situations. Adults are present year-round; they overwinter out of water among litter or under debris etc, are active over a long season from March until October or November, peaking in abundance during May and again in the summer. A proportion of adults are capable of flight; they have been swept from marginal vegetation and they occasionally appear in light traps on warn spring and summer evenings. Adults are detritivores or vegetarian, and the predaceous larvae have been described by Bøving and Henriksen (1938). From the phenology it is likely the species is univoltine with reproduction occurring in the spring, but the biology remains unknown. Adults may be found among marginal vegetation, often in very shallow water and sometimes in temporary pools or even puddles in the spring, they usually occur in numbers and good samples should be taken as they often alongside the common and widespread L. bipunctatus or other members of the genus.
2.5-3.2 mm. Convex, broadly-oval and more-or-less continuous in outline, head dark with a small pale patch in front of the eyes, pronotum pale with an extensive and irregular dark discal mark which extends to the apical and basal margins, elytra pale with rows of dark lines or dots, often extensively darkened but usually with paler margins and always with a small pale area at or near the apex. Forebody distinctly microsculptured (X40). Head finely but not densely punctured between large and weakly-convex eyes that follow the outline, clypeal margin straight, labrum smoothly curved apically. Palps yellow with the extreme tip darkened, at least as long as the antennae, terminal segment distinctly longer than the previous segment. Antennae 8-segmented, yellow with a dark 4-segmented club. Pronotum widely transverse, broadest across slightly obtuse (from above) posterior angles and smoothly narrowed to projecting anterior angles, apical and basal margins smoothly curved and simple. Pronotal surface smoothly convex, punctured about the same as the head, but with a series of close set punctures in front of the basal margin. Elytra broadest about the middle and smoothly curved from rounded shoulders to a continuous apical margin, each with about 20 regularly punctured striae, these may be confused around the scutellum but they otherwise form regular rows, interstices narrow and smooth. Legs long, slender and entirely pale brown or yellow, Front tibiae with external spines and short apical spurs, middle and hind tibiae with long and paired apical spurs, and only fine external setae. Tarsi 5-4-4, all segments simple except front tarsomeres 2 & 3 dilated in males.