Mycetophagus atomarius (Fabricius, 1787)
Widely distributed across England, Wales and Scotland as far north as Glasgow but with few records from Wales and the west country and not recorded from Cornwall. Associated with fruiting bodies of Daldinia concentrica on Ash (Fraxinus) and Hypoxylon fragiforme on Beech (Fagus). Larvae develops within the fungus and pupae are reported from under bark or in deadwood (Alexander). Joy states simply "under Beech bark", a habitat we have sampled extensively around Watford without producing the species, to find the beetle one needs to find the fungus, in our experience searching Beech otherwise appears pointless. From our experience a very local species despite at least one of its hosts, Daldinia, being common throughout our area. All our records are from Daldinia on the western border of Cassiobury park during March and April.

3.5-4.5mm. Antennae red with segments 7-10 black, broadened apically into a weak 5 segmented club. Inserted under sides of head in front of eyes, insertions widely separated. Head black, widest at eyes and strongly punctate from hind margins of eyes forward, behind this with five transverse lines and then strongly microsculptured to base. Hind margins of eyes with erect dark setae. Labrum and palpi red. Thorax less closely punctured than head and finely bordered throughout. Broadest at base with sides evenly rounded and smooth, not crenulate. With large basal fovea, hind margin strongly sinuate. Black or narrowly red anteriorly. Elytra with strongly punctate striae and dense microsculpture (X20), yellow marks narrow and characteristic at shoulders and behind middle. Entire upper surface somewhat shining and with recumbent yellow pubescence. Legs yellow and pubescent, apex of each tibiae with two small spines. Male tarsi 4-4-4, female 3-4-4. Claws simple.

Description from 2 Watford specimens at X20