Tanysphyrus lemnae (Paykull, 1792)
In Europe Tanysphyrinae consists of a single genus containing two species of which one, Tanysphyrus lemnae, is widely distributed throughout England north to Yorkshire. Associated with Duckweed (Lemna spp.) on which the larvae feed. Specific associations are uncertain but we have found adults, and often in numbers, among Lemna minor throughout the Watford area. They may be swept from waterside vegetation growing near to wherever the host is present or, despite the fact that adults cannot swim (Morris, 2002), extracted from Lemna samples taken at any distance from the water's edge. They become active during warm days in early March and by April or May depending on season are common and remain so until at least mid July when numbers fall. Adults are common in samples of vegetation throughout the winter, sometimes unexpectedly so e.g. from grass tussocks growing upon logs at least a hundred metres from water (Cassiobury park, 10/02/07). Several were found under the bark of a submerged log along with many Haliplus and several Stenus fornicatus in a Cassiobury park pond during April 2007.

1.4-1.9mm. Characterised by the terminal tarsal segments; third strongly bilobed so that the small terminal segment protrudes very little, and sometimes not at all, beyond its apices. The small claws add to the impression of truncate tarsi under a hand lens. Rostrum punctate and long, about as long as pronotum, broadened to apex. Scrobes narrowly visible from above towards apex. Antennae inserted beyond middle, nearer apex in male. Funiculus 7 segmented and club very large. Pronotum broadest at middle, coarsely and densely punctate and usually with lighter scales in an indistinct longitudinal line either side of middle. Elytra with deeply impressed striae, each stria with small, curved semi-erect dark setae. Without erect scales. Parallel sided or slightly dilated behind and with various indistinct patches of light pubescence. Legs robust and finely pubescent, red with femora darker. Femora not toothed below, protibiae with well developed inwardly produced apical tooth. Claws free (not connate) and simple. Male rostrum slightly shorter and less shining than female.

Description from 3 Watford at X50