Rhizophagus bipustulatus (Fabricius, 1792)
Common and often very common throughout southern England, less so in the north and south west Scotland. Adults are found beneath bark, both healthy and otherwise, or among fungi associated with this. Predominantly among deciduous bark but occasionally from conifer, around Watford common under dead Beech and Oak but also from fallen pine in Whippendell wood. Seemingly absent during the winter. Our first records are from late March, by April the adults are common and usually found in small groups.
Also recorded from Elm, Alder, Birch, Malus spp., Poplar and other trees. They are most readily found at the boundary between healthy and dead bark.

2.0-3.5mm. Antennae light brown, as legs, club rounded (stepped) at apex and first joint large. Third segment about as long as four and five together. Head dark brown and punctate, width across eyes less than greatest width across pronotum (R.dispar). Frons with weak depressions inside eyes. Pronotum elongate, widest in front of middle and with front angles rounded, not produced. Strongly bordered laterally and basally, punctate throughout with all punctures about the same size. Elytra dark with (to varying degrees) pale shoulders and subapical macula, not so strongly tapering as in R.dispar, and with shallow oblique subhumeral depressions- the insect needs to be tilted forward and illuminated from in front to see this. Striae punctate, second internal without punctures but for an occasional one in the basal quarter. Legs of medium length with tibiae broadened towards apex; mid and hind tibiae straight on outer side or very nearly so and with several small spines. Inner edge of hind tibiae angles in male, straight in female.

Typical specimens are readily identified in the field from the colouration; legs, antennae and front of head light against a dark body and with light subapical macula. Atypical or immature specimens can be identified from the above description.

Description from 6 specimens at X20