Rhizophagus nitidulus (Fabricius, 1798)
POLYPHAGA Emery, 1886
CUCUJOIDEA Latreille, 1802
RHIZOPHAGINAE Redtenbacher, 1845
This is a widespread though sporadic and generally very local species in Europe, it is locally common in Central and Northern Europe, reaching the UK and central provinces of Fennoscandia, but very local and mostly confined to mountain areas across the south from the Pyrenees to Greece, it is present on many of the Mediterranean islands but absent from North Africa and the Atlantic islands, and further east it reaches into Ukraine and to high latitudes in Western Russia. In the UK it is locally common across South East and Central England and Wales and more sporadic and scarce across the rest of England including the Isle Of Wight but not Anglesey or Man, it is very local and rare in Scotland although here it may be increasing, but is absent from Ireland. Adults are present year-round, they overwinter under bark or among decaying wood and are active over a long season from early spring. Typical habitats are open deciduous woodland or wooded parkland although on the continent they are more likely to occur on conifers at higher altitudes, but they may also occur on isolated trees in hedgerows or on pasture, adults fly and are crepuscular and nocturnal, usually occurring in small numbers or as single specimens. Adults often occur near fungi and so the species is sometimes quoted as mycophagous, but both larvae and adults most often occur under bark that has been attacked by or hosts other subcortical beetles, and in Northern Europe the adults often occur in large numbers in traps baited with pheromones used to attract species of Trypodendron Stephens, 1830 (Curculionidae, Scolytinae). On the other hand they have been recorded at sap runs on both broadleaf and coniferous trees and have been attracted to fermenting substrates and so the biology thus remains ambiguous. Adults may be found by night when they often wander on exposed wood or bark, they sometimes occur under bark during the day but more usually within crevices where they are very difficult to find.
Rhizophagus nitidulus 1
Rhizophagus nitidulus 2
Rhizophagus nitidulus 3
Rhizophagus nitidulus 4
© Lech Borowiec
3.0-4.7mm. Similar to other members of the genus and so microscopic examination will be required for certain identification but many specimens are characteristically coloured and the form of the middle and hind tibiae is a good field guide to the species. Body glabrous and entirely pale reddish-brown, usually with the pronotal disc and apical half of the elytra extensively darkened, appendages entirely pale brown. Head evenly convex between large (for this genus at least) and protruding eyes, temples long and weakly converging, surface finely and evenly punctured throughout. Antennae inserted laterally in front of the eyes, 11-segmented with the basal segment large and curved internally, segments 4+5 together about as long as 3, and segments 9-11 forming a distinct club with all segments plainly visible. Pronotum elongate and slightly curved laterally to rounded angles, surface weakly convex and rather flattened across the disc, punctures fine and evenly distributed throughout. Elytra smoothly narrowed from finely rounded shoulders to a continuous apical margin which usually leaves the pygidium exposed, striae punctured and more or less parallel throughout and interstices flat or only very weakly convex. Legs long and robust with femora are broadly visible from above, front tibiae produced to an external apical tooth, middle and hind tibiae curved externally before projecting and truncate apices (characteristic of this species). Tarsi without bilobed segments; 5-segmented in females, 5-5-4 in males, claws smooth and without a basal tooth.