Pseudotriphyllus suturalis (Fabricius, 1801)
This generally rare species has a mainly southern distribution in Europe, extending from Spain, where it is known from only a few records, to the Balkans, Greece, Romania and Ukraine, and to the north extending to Germany, the UK and possibly Poland although records there are not confirmed. Across much of this range it is very rare e.g. it is classed as critically endangered in Germany and as near-threatened in Austria, but in the UK it is widespread and sometimes locally common in central and eastern England; it is absent from most of the southern coastal counties and the West Country and sporadic and very scarce further north to south-east Scotland. Our local park and woodland in Watford, South Hertfordshire, would therefore seem to be a hotspot for the species as it has been abundant here each year since 2005 and is probably the commonest local member of the family. Typical habitats are old established woodland and wooded parkland and pasture where the beetles occur among fruiting bodies of the fungus Laetiporus sulphureus (Bull.) Murrill (1920), usually on injured or decaying parts of oak or beech but sometimes on other broadleaf trees, adults are present year-round and may be abundant through the winter. Adults are nocturnal and attracted to the fungus in all stages of development and decay; they are easily observed at night on the surface of fruiting bodies or tapped into a net during the day, they often occur under bark near the fungus and they also remain on dry and crumbly parts of the fungus that have fallen to the ground in the summer, and when this becomes waterlogged and slimy through the winter the beetles remain in numbers among the decaying tissue or in surrounding leaf-litter. Adults often seem to be more abundant through the winter and unlike the rest of the year they are often the only beetle species present, extractions of suitable material almost always produce numbers of adults and they sometimes occur among extractions of other fungi. On the continent they have also been recorded from the following fungi, Cerioporus squamosus (Huds.) Quélet (1886), Fistulina hepatica (Schaeff.) With. (1792), Pleurotus ostreatus (Jacq. Ex Fr.) and Phallus impudicus L. (1753).
Adults are small, at most 3mm, elongate-oval and moderately convex, the body is dark to pale brown or reddish-brown, usually with the head and pronotum darker, and the entire dorsal surface is finely punctured and pubescent, and the antennae and legs are pale brown. Head slightly narrower than the apical margin of the pronotum and mostly concealed from above, vertex and frons rather flat and eyes large and convex. Antennae inserted laterally in front of the eyes, the two basal segments only a little broader than those following, segments 1-5 elongate, 6 quadrate, 7 and 8 transverse and 9-11 transverse and much broader, forming a distinct 3-segmented club. Pronotum broadest near the base and gradually narrowed to a straight apical margin, the anterior angles not visible from above, lateral margins finely crenulate, posterior angles only weakly sinuate and the surface with two shallow but obvious fovea towards the base. Elytra broadest about or a little in front of the middle and smoothly curved laterally from rounded shoulders to a continuously curved apical margin, surface without striae; the punctures a little stronger than those on the pronotum and randomly arranged throughout. Legs long and slender, the tibiae only weakly broadened and with tiny apical spurs, female tarsi 4-segmented, male tarsi 3-4-4, the segments not obviously bilobed, claws smooth and without a basal tooth.