SCAPHIDIINAE Latreille, 1806
The five British species of this distinctive Staph group are all associated with decaying wood and fungus. Three are locally common and widespread, while the other two are very infrequently recorded.
This is a large subfamily of 45 genera and about 1500 species. It is classified into 4 tribes with the majority, about 37 genera, included in the Scaphisomatini Casey, 1894. The Cypariini Achard, 1924 includes about 60 mostly tropical species in the single genus Cyparium Erichson, 1845, Scaphiini Achard, 1924 includes 3 Palaearctic and tropical genera while the Scaphidiini Latreille, 1807 includes 4 genera with most of the species in the large genus Scaphidium Olivier, 1790. The subfamily is cosmopolitan with the greatest diversity in Old World tropical regions, the Western Palaearctic is relatively poor in species; about a dozen occur in central Europe while 70 species if 4 genera occur in the United States. Some areas are rich in endemics e.g. of the 23 species recorded in New Zealand 21 are endemic. The group was formerly regarded as a distinct family but is now included in the Staphylinidae on larval characters and male genitalia morphology. All species are believed to be mycophagous and most are associated with decaying wood in forest and parkland etc. where both adults and larvae develop either in fruiting bodies or by grazing spores, mycelia and slime-moulds, some have specific host associations and some African and Asian species occur in nests of fungus cultivating termites. They are unusual, though not unique, among the family in that the elytra are almost entire, being generally to some extent truncate apically, leaving only one or two abdominal segments exposed. Temperate species are mostly drab and shiny insects; pale testaceous to black or black with various red or yellow markings, and some e.g. the Western Palaearctic Caryoscapha limbata (Erichson, 1845) (formerly included in Scaphisoma) are metallic. Tropical species may be strikingly coloured e.g. the Mexican Cyparium navarretei Fierros-Lopez, 2002 is black with the elytra and abdomen bright red, and Scaphidium variable Matthews, 1888 from Panama and Costa Rica is entirely shiny yellow with black markings and bicoloured legs. Scaphidium morimotoi Löbl, 1982 from Paraguay has distinct allopatric colour forms. The subfamily may be recognized by the characteristic broad-oval and compact body, long and slender legs and antennae which are inserted on the front of the head outside the base of the mandibles, the insertions being visible from above, and the form of the antennae; 11-segmented with the last 5 segments modified into an elongate club or each variously expanded internally. The mouthparts are
hypognathous, which is unusual in staphylinids, and the eyes vary from round to reniform, in many curving around the antennal insertions. The elytra lack distinct striae although there may be rows of punctures and there is usually a well-defined and impressed sutural stria. They are generally small, <10mm and many are tiny, <2mm. The U.K. fauna includes 5 species in 3 genera although Scaphium immaculatum (Olivier, 1790) has not been recorded since 1936 and Scaphisoma assimile Erichson, 1845 since 1974, and both may now be extinct. The common and widespread Scaphidium quadrimaculatum Olivier, 1790 is distinct; black with two red marks to each elytron, and should soon be recorded when searching decaying logs and fallen timber. Our 3 genera represent a significant proportion of the world fauna, if not its diversity; the cosmopolitan Scaphidium Olivier, 1790 includes about 270 species, the Holarctic and Afrotropical Scaphium Kirby, 1837 includes 4 species and the cosmopolitan Scaphisoma Leach, 1815 includes about 550 species; 13 occur in Europe of which 8 extend to central Europe and 3 to the UK.
The following key can be used to identify the British species:
Size larger >4mm. Antennomeres 9 and 10 transverse.
Size smaller<2.5mm. Antennomeres 6-11 elongate and expanded internally.
Elytra black with red markings, punctation random.
Elytra entirely black, with puncture rows.
Sutural stria curved but abbreviated at the basal margin, hardly extending beyond the scutellum.
Sutural striae curved and continued along the base of the elytra to 1/3 or ½ way.
Elytra black and densely punctured. (Aedeagus distinctive)
Elytra paler, dark brown to reddish, and less densely punctured. (Aedeagus distinctive)