Scydmoraphes Reitter, 1891
This large Palaearctic genus includes more than 120 species and subspecies; the greatest diversity is in the west, and Europe in particular where more than 75 species and subspecies have been recorded although most of this diversity is in Mediterranean regions. Many have limited distributions or are endemic to certain countries or islands e.g. S. tenuicornis (Reitter, 1881) from Sardinia and Corsica, or S. titan (Reitter, 1881) from Spain, and only about ten species extend north into central Europe. Two widespread species extend north into the UK, see below. All species are ground dwelling and most occur live among woodland litter or in moss or decaying wood but a few are sometimes associated with ant nests. The species are tiny and have secluded lifestyles and so are likely to be under-recorded. Little is known of the biology but adults usually occur year-round and, typical of the family, they are thought to be specialist mite predators, and the larva of S. sparshalli has been described (Jaloszyński, 2015).
They are small beetles, at most 2.0 mm but the majority are much smaller, less than 1.3 mm. The general appearance is typical of much of the subfamily; elongate and discontinuous in outline with the head slightly narrower than the pronotum and the pronotum much narrower than the oval elytra, body finely pubescent, black to brown or with a mixture of both, appendages brown, Head finely punctured and convex to slightly concave between large, convex and coarsely-faceted eyes, temples moderately converging to a wide neck (which is at least 2/3 as wide as the head across the eyes), anterior clypeal margin often with lateral or median ridges, labrum truncate apically. Maxillary palpi 4-segmented; third segment enlarged and the fourth segment small and slender. Antennae inserted laterally in front of the eyes. Antennae 11-segmented; 2 basal segments only a little broader then the fourth segment, third segment narrower than two and four, 5-7 quadrate or slightly elongate, and 8-11 form a long and loose club, in some specimens the eighth segment is only a little wider than the seventh and so the antennae appear to be gradually thickened
Scydmoraphes helvolus 1
Scydmoraphes sparshalli 1
Scydmoraphes helvolus 2
apically or to have a 3-segmented club. Pronotum quadrate to slightly elongate, broadest behind rounded anterior angles and narrowed to perpendicular or slightly obtuse posterior angles, lateral margins finely bordered, surface finely punctured throughout and with an uninterrupted transverse groove across the base. Met-episterna covered, or mostly covered, by the elytra and so not visible in lateral view, hind coxae closely approximated and wide, reaching the elytral margin or nearly so. Elytra smoothly curved from sloping shoulders to separately curved or continuous apical margins which substantially cover the abdomen, epipleura reflexed and not demarked by a ridge, surface with glabrous basal fovea and a longitudinal impression from the shoulders, finely punctured and often uneven. Legs long and slender with tarsi almost as long as the corresponding tibiae, all tarsi with five simple segments. Among our UK fauna very similar in habitus to Stenichnus, which have simple (unbordered) pronotal margins, or Neuraphes, in which the transverse pronotal impression is either keeled or interrupted medially and the elytral fovea are pubescent. The species tend to look very similar and identification often depends on genitalia examination, but our two UK species are readily distinguished as:
Smaller, 1.3 mm at most. Head weakly convex or flattened anteriorly, the antennal tubercles distinct but flattened and only slightly raised. Aedeagus distinct.
-S. helvolus (Schaum, 1844)
Larger, at least 1.3 mm. Head distinctly flattened anteriorly with antennal tubercles appearing raised. Aedeagus distinct.
-S. sparshalli (Denny, 1825)
Scydmoraphes helvolus is widespread in Europe from France to Romania in the south and extending north into the UK, Denmark and southern provinces of Fennoscandia; there are widely scattered records from many countries but it tends to be very local and scarce throughout the range. The species occur very locally across southern and central England and Wales and is most frequently found in the south east and East Anglia. Adults occur year-round with peaks in abundance occurring in spring and autumn. Typical habitats are established deciduous woodland and wooded parkland; adults occur under loose bark or among moss and leaf-litter, often around mature oak trees, and, at least on the continent, they have been recorded from nests of Wood ants (Formica rufa L.) and Black ants (Lasius fuliginosus (Latreille,)). Sampling is usually by sieving or taking likely samples for extraction but adults have also been recorded from winter flood refuse.
Scydmoraphes sparshalli This is a mostly Central European species; it is known from the Pyrenees to Northern Italy and Romania in the south and north to the UK, Germany, Denmark and the Netherlands in the north; it is generally absent from the Baltic region although there are records from Latvia and the extreme south of Sweden and Finland. The species is very rare in the UK and known from only a few sites across central England and Wales although it is also recorded from Lundy Island. Adults have been recorded from January until the autumn but they probably occur year-round. They are associated with woodland and wooded parkland and pasture etc. and they have been recorded under bark of a range of deciduous trees including oak and alder, on the continent they have also been recorded from decaying hay on pasture near woodland margins, rodent passages and ant nests (Lasius fuliginosus Latreille, and probably other Lasius species.)