Description

Most of the species are tiny, 1-3mm but some tropical species can reach 5mm and, despite the wide morphological variation, they soon become recognizable due to the characteristic broad head and pronotum and the usually obvious raised lines on the forebody and often the elytra. Shape very variable, most species are oval to elongate and very flat although e.g. the African Mestolaemus longicornis Lefkovitch, 1962 is unusual in having short and almost round elytra, and a few genera e.g. Leptophloeus Casey, 1916 or Dysmerus Casey, 1884 are long and almost cylindrical being adapted to living in galleries rather than under bark. Most are drab brown to black although there are many colourful, or at least maculate, species e.g. the Palaearctic Laemophloeus monilis (Fabricius, 1787), the Nearctic L. fasciatus Melsheimer, 1884 or species of the Nearctic genus Rhinophloeus Sharp, 1899. The head is generally comparatively large and transverse although in the Nearctic and African Nartheticus LeConte, 1861 it is very elongate and in Rhinolaemus maculatus Steel, 1954 from Fiji the head is produced in front of the eyes. The mandibles are large, robust and often produced anteriorly, sometimes e.g. in Rhinolaemus Steel, 1954 very strongly so, with 2 or more variously developed apical teeth and sometimes a sub-apical tooth. The maxillary palps are 4-segmented and the labial palps are 3-segmented and in each case the terminal segment is the longest. Eyes very variable, usually convex and protruding, in Odontophloeus Thomas, 1984 species very well defined, and in some species e.g. members of the widespread genus Narthecius LeConte, 1861, flattened, in many species they are asymmetric and have large facets. There is at least one lateral carina beside the eyes – typical of the family – and the frons is often expanded, sometimes very widely so, for example Dysmerus basalis Casey, 1884. A frontoclypeal suture is sometimes present, for example in species of Placonotus Macleay, 1871, and the labrum is large; the anterior margin rounded to truncate or strongly emarginate, some species have a long and well-developed rostrum, for example members of the Neotropical genus Rhinomalus Gemminger in Harold, 1870. The antennae are 11-segmented, or rarely 10-segmented, and always well-developed and vary in form, for example very long and filiform in Mestolaemus longicornis Keftovitch, 1962, or shorter and filiform in, for example Rhobdophloeus horni Sharp, 1899, indistinctly clubbed, for example in Leptophloeus angustulus (LeConte, 1866) or distinctly clubbed, for example in the new-world genus Lathropus Erichson, 1845. They are often sexually dimorphic, varying in length or the proportion of various segments, or otherwise modified, for example the basal segments in males of tropical species of Cryptolestes Ganglbauer, 1899; in C. calabozus Thomas, 1988 or C. unicornis (Reitter, 1876), but probably most developed in C. diemensis (Blackburn, 1903) where the basal segment is large and arcuate; almost semicircular. Temples variable, sometimes long but almost always strongly constricted. Pronotum quadrate to elongate, generally broadest in front of the middle and strongly narrowed towards the base, the anterior and posterior angles are usually well-formed and sometimes produced. The surface is variously punctured, often strongly so, but the cuticle is generally smooth between, and there is at least one sub-lateral carina. The lateral margins vary greatly; Often smoothly sinuate but sometimes denticulate, for example in Mestolaemus Lefkovitch.... or the Palaearctic Laemophloeus monilis (Fabricius, 1787), in Odontophloeus Thomas, 1984 the lateral margin has four large teeth. Scutellum transverse to triangular. Prosternum broad and flattened with a broad process, the coxal cavities variable. Mesosternum short and broad, the coxal cavities broadly separated and usually opened laterally. Metasternum elongate, usually with a complete median longitudinal line. Anterior coxae obliquely transverse, mid coxae round and globular, hind coxae transverse. Elytra covering the abdomen and usually rounded at the apex, the humerus well-developed. Surface smooth to randomly punctured, or with variously developed striae, longitudinal carinae, pubescence or rows of stiff setae, but never with a scutellary striole. Femora well-developed, tibiae robust; often swollen and usually with strong equal or unequal apical spines, especially to the pro- and meso-tibiae. Tarsi in males usually 5-5-5, sometimes 5-5-4, in females 5-5-5; basal segments short. Claws well-developed.