Anacaena globulus (Paykull, 1798)

A common and often very common species throughout the British Isles including Lundy, Anglesea, Man, the Western Isles, Orkney, Shetland and, although Balfour Browne states that it is seldom found in brackish water, its distribution includes almost all coastal regions (NBN). Hansen states that it is occasionally found in seashore drift and may occur more especially in acid water. Berge Henegouwen (1986) gives simply all kinds of permanent and semipermanent water to 2000m. Generally the species seems to show no particular preference for water type, being found in highland sphagnum pools (Balfour-Browne) and all types of freshwater although, from experience, they may be more frequent at the margins of running water. They are found throughout the Watford area, generally in small numbers and often in company with the much more numerous (locally at least) A.limbata (Fab.). Sweeping aquatic or marginal vegetation along local rivers or around any standing or slow moving stagnant water will produce them from mid April, depending on season, and they remain active at least until November. Adults are also present through the winter; they may be extracted from the remains of waterside vegetation and are common (2006/7) in reed litter samples from Radlett road, again in most cases they occur among much larger numbers of A.limbata. Placing logs or timber into marginal water is a good way to record them in winter; each time we have done this in the Cassiobury park pond both Anacaena species have appeared within a week or so. They are occasionally recorded during the summer at MV in town centre gardens.

The convex form and abruptly yellow pronotal margins will, with a lttle experience, allow identification in the field. (See IDAids)

2.7-3.5mm (Henegouwen gives 2-3.3mm). Broadly oval and convex, more so than in other Anacaena species. Outline entire, dorsal surface shining and not, or only very slightly, metallic, finely and rather densely punctured. Head black or with pale patches before the eyes (Balfour-Browne), more densely puntured than pronotum. Eyes not protruding, front and hind margin incised. Head narrowed in front of eyes, clypeus weakly emarginate, labrum more strongly. Antennae nine segmented with a pubescent three segmented club, testaceous with club black. Maxillary palpi as long as antennae, terminal segment a little longer than penultimate, testaceous with terminal segment darker. Pronotum transverse (13:5), broadest at base and finely bordered. Black with abrupt yellow margins, the yellow usually continuing along the basal margin to about a third. Front and hind angles rounded. Scutellum equilateral and finely punctate. Elytra broadest near middle, entire and with apices right angled. Black with pale margins, apex often extensively pale and usually with rows of black spots. Unpunctured sutural stria deeply impressed apically, weak or absent in basal third, without other stria. Puncturation random and fine, as pronotum. Legs dark red or brown. Protibiae rounded apically, with four strong spines towards apex on outer side. Meso and meta tibiae with strong spines throughout and long apical spurs, without swimming hairs. First tarsal segment small so that tarsi appear four segmented. Protarsal segments 2-4 equal, fifth large. Meso and meta tarsal segments 2 and 5 longer than 3 and 4. Claws smooth, toothed at base.

Description from 4 Watford specimens at X40

Berge Hengouwen, A.L.van 1986. Revision of the european species of Anacaena. EntScand. 17:393-407.