*polypoda (Linnaeus, 1766)
Ptenothrix atra seems to be rare. Although there are a few scattered literature records for this species, it is quite easy to confuse with Dicyrtoma fusca. There is only one definite specimen from Britain in the NHML slide collection found at Boxhill in Surrey by Bagnall in October 1943. Unfortunately, the antennae of this specimen are poorly preserved. In 2009 Paul Ardron found a specimen of thisspecies in woody detritus at Swallow Wheel mill, Rivelin valley, Sheffield.
Members of the Dicyrtomidae are characterised by having a very short fourth antennal segment. In Ptenothrix atra, the third antennal segment (ant3) is clearly subdivided (ant3 is not subdivided in Dicyrtomina fusca). The claw on the foot is not wrapped in an outer membrane and the empodium bears a long filament that reached beyond the tip of the claw (Fig. 1). The inner and outer edges of the mucro are serrated (Figs. 2, 3) and the setae on the outer edge of the dens are smooth (Fig. 4) (these setae are feathered in Dicyrtoma fusca). The spines on the abdomen are relatively long (Fig. 5) and the dorsal side of abd6 (Fig. 6) bears long erect setae (not present in Dicyrtoma fusca).