Description

Adult limnichids are small, up to 3mm, elongate-oval and convex dorsally, most are uniformly brown to black, usually with pale appendages, and clothed with fine golden to grey pubescence or scale-like setae. The head is weakly to strongly hypognathous and usually proportionally small, rarely larger as in Limnichites Casey, 1889, and usually deeply inserted into the prothorax so appearing transverse from above. Vertex flat to weakly impressed or convex, eyes round, small to large and usually rather flat, inserted on the lateral margin and so visible from above although sometimes e.g. in Eulimnichus Casey, 1889, hidden, and usually setose. Frontoclypeal suture faintly impressed or obliterated, clypeus distinct, labrum short and transverse. Antennae 11-segmented and short, most segments broad, and with a 1-7 segmented club, inserted between the mandibles and the anterior margin of the eyes. Mandibles small and usually hidden, maxillary palpi 4-segmented, labial palpi 2 or 3 segmented, all segments elongate and slender. Pronotum transverse to almost quadrate; broadest at distinct and usually sharp posterior angles and narrowed to anterior angles which are often produced forward, surface variously punctured and evenly convex or with distinct median or lateral basal impressions, the lateral margins bordered and the basal margin sinuate or bisinuate. Prosternum broad and flat to very convex in front of oval to transverse and posteriorly open coxal cavities, the process extending to at least the hind margin of the cavities, and often fitting into the anterior margin of the mesosternum, acute to bluntly pointed. Mesosternum short and transverse, the cavities round to oval, and widely separated. Metasternum broad and deep in front of transverse and narrowly separated or contiguous coxal cavities which generally extend to the elytral epipleura, sometimes with a longitudinal median impression. Abdomen with five visible sternites; all free and articulated. Pro-leg trocanters well-developed and exposed, meso- and meta-trocanters moderate and triangular. Femora and tibiae slender, both very variable in length. Tarsi 5-5-5, without bilobed segments, claws simple. In most species the underside is grooved for the reception of the legs, and the antennae generally reflex under the anterior pronotal angles. Scutellum small but distinct and usually triangular. Elytra convex, generally without prominent shoulders, and evenly curved to a continuously rounded apex, generally reflexed laterally and bordered outside well-developed epipleura. Surface randomly and usually quite finely punctured, sometimes with indistinct rows of punctures but without distinct striae.

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Larvae are small, less than 5mm when fully grown, elongate and sub-cylindrical, weakly curved and usually pubescent. Pale with the head generally darker, prognathous and partly retracted into the thorax. Antennae 3-segmented and short, the terminal segment with an apical spine. Clypeus and labrum transverse. Mandibles bi- or tri-dentate and lacking a molar or basal tooth. Maxillae with 4-segmented palps, labium transverse with 2-segmented palps. Thorax generally a little wider than the head, with short 5-segmented legs bearing a single moveable claw. Abdomen parallel-sided and decurved towards the apex; segments 1-7 with broad membranous sterna, sternum of segment 8 narrower, sternum 9 operculiform and lacking gills. Posterior margin of all thoracic segments, and abdominal segments 1-8 with longitudinally-striated borders, terminal abdominal segment without cerci. The larvae are semi-aquatic, living among decaying plant material at the water margin, among moss or in tunnels in sandy or silty and waterlogged substrates which are covered with algae and mosses. They are thought to consume decaying plant material among the substrate or to graze the surface mosses from below. Pupation occurs in the same habitats.