PATROBINAE Kirby, 1837
Includes one widespread species (P. atrorufus) and two upland species which have more restricted, northern ranges in the UK.
The subfamily Patrobinae is thought (variously) to be a sister-group of the Trechinae based on the structure of the abdomen and the male tarsi as well as larval morphology, it includes 2 tribes of which the majority of genera and species are included in the Patrobini, the Lissopogonini includes about 10 species of the Asian genus Lissopogonus. Patrobini is an extensive tribe of about 235 species and many subspecies in 27 genera and (tentatively) 4 subtribes, two of which are monogeneric. Platidiolina Zamotajlov & Lafer, 2001 includes 5 species of Platidiolus Chaudoir, 1878 from Asia (4 spp.) and North America (1 sp.) while Deltomerodina Zamotajlov, 2002 includes 14 species of the central Asian genus Deltamerodes Deuve, 1992. Deltomerina Chaudoir, 1871 includes 10 genera, about 115 species many subspecies, it is Holarctic in distribution with all but one genus and with the vast majority of species occurring in Asia, it is represented in Europe by 9 species of Deltomerus Motschulsky, 1850 (a Palaearctic genus of more than 90 species and many subspecies) and 5 species of Penetretus Motschulsky, 1865 but none occur in the UK. Patrobina Kirby, 1837 includes 15 genera and about 100 species, with the exception of the monotypic genus Platypatrobus and 7 species of Patrobus Dejean, 1821, which occur in the Nearctic region, the group is Palaearctic with a few species extending into the Oriental region, the majority occur in eastern areas and Japan is particularly rich in species with 2 genera endemic to that country; Apatrobus Habu & Baba, 1960 (20 spp.) and Minypatrobus Uéno, 1955 (4 spp.), the European fauna includes 7 species of Patrobus, of which 3 extend to the UK.
Patrobus is the only UK representative of the subfamily, it includes 17 species and is most diverse in Asia, our 3 UK species are widespread and all extend into Asia while the remaining European species are mostly of very restricted distribution. All are medium sized ground beetles, 6.5-10.0mm, elongate and rather nondescript shiny but not metallic black or dark brown species with large eyes, cordate pronotum and elongate elytra with well-impressed striae. Head with large convex eyes and short temples strongly converging to a short neck, vertex with a transverse punctured area behind the eyes, with 2 supra-orbital punctures and deep, slightly converging frontal furrows. Terminal segment of all palps well-developed, mandibles sharply pointed, with a setiferous puncture on the external
margin, and antennae pubescent from the third segment. Pronotum transverse and cordate with deeply impressed and usually wide basal fovea delimited externally by a short keel, lateral margins narrowly bordered and with a setiferous puncture about the middle and inside the posterior angle, disc with a transverse impression behind the anterior margin and a longitudinal impression that often widens towards the base. Elytra without a basal margin inside the shoulders, with complete and usually finely punctured striae and a short scutellary striole, interstices flat or weakly convex, the third with 3 or 4 setiferous punctures. Wings variously developed. Fore tibia with a deep antennal-cleaning notch and a single apical spur. Male with two basal pro-tarsomeres dilated. Our UK species may be separated with the following key:
-7.4-10.0mm, entirely black or with the forebody darker than the elytra (in mature specimens), suture sometimes darkened. Wings fully developed. [More slender when compared with our other species, with a shorter and less sinuate pronotum and slender, more parallel-sided elytra. The transverse groove behind the anterior pronotal margin deep, the anterior margin appearing distinctly raised.]
P. septentrionis Dejean, 1828
-6.5-9.5mm. Body entirely dark brown. Wings reduced, at most shorter than the elytral length. [More robust in appearance, the transverse impression behind the anterior pronotal margin weaker, the anterior margin appearing only slightly elevated.]
-7.4-9.5mm. Third antennomere more slender and distinctly longer than the basal segment. Raised area between the frontal furrows and the side margin wider anteriorly (view from in front). Head and pronotum without or with only very faint transverse wrinkles. [Entirely reddish brown to dark brown, appendages and often the elytral suture pale red. Elytral striae more finely punctured.]
P. atrorufus (Ström. 1768)
-6.5-9.0mm. Third antennomere wider and about equal in length to the basal segment. Raised area between the frontal furrows and the side margin parallel-sided. Head and pronotum with distinct transverse wrinkles. [Dark reddish-brown with the appendages a little lighter. Elytral striae more coarsely punctured anteriorly.]
P. assimilis Chaudoir, 1844