Orthoperus atomarius (Heer) rediscovered in Britain and Orthoperus aequalis Sharp in Devon (Corylophidae: Orthoperinae)

摘要

The genus Orthoperus Stephens, 1829 contains six of the smallest beetle species in Britain, the species discussed here are 0.56-0.77mm long. Orthoperus are generally found in damp habitat with vegetative matter and are often associated with mould. Their small size impedes not only their discovery but their identification although this is significantly eased by Bowestead's (1999) detailed text and the good nature of the few who have spent time identifying them. It should be noted that because of their small size they are, inevitably, under-recorded. I first encountered and dissected an Orthoperus found amongst broken up and sieved damp bracket fungus Ganoderma resinaceum Boud. found on an old oak stump at Maristow, Devon (SX4764, VC 3) on 13 November 2010. After painstakingly searching through a pillowcase of debris I had amassed 8 individuals of this minute beetle, the pain in painstaking being accentuated by the numerous sharp stings I suffered from the very active horde of minute parasitic wasps breeding in the abundant Cis (Ciidae) population. I sent ten examples of the bethylid to James Hogan of the Oxford Museum of Natural History who identified them as Cephalonomia formiciformis Westwood (Hymenoptera: Bethylidae) (accession number OUMNH-2011-031), a species not seen in Devon since 1929 and apparently the first record from south western Britain in 77 years (Richards 1939, BWARS, 2014; NBN, 2014). With regard to the beetle I took the advice of Roger Booth of the Natural History Museum, London (BMNH). He was generous enough to spend some time looking at the dissected material and explained that it was Orthoperus aequalis Sharp. This is the first record for Devon and appears to be the first in south-western England, the nearest locality being the New Forest, Hampshire (NBN Gateway, 2014; Hyman, 1992; Bowestead, 1999). It is also the first association of the beetle with Ganoderma resinaceum, a rare fungus in south-western Britain. My identification of the fungus was confirmed by Jeff Benn, the Chairman of the Devon Fungus Group. The beetle has previously been found in Britain on oak bark with mould, cut oak pieces, freshly sawn beech, on fermenting plums and under bark of: a dead elm, birch, a damaged sycamore with mould, oak with mould, beech & fire damaged sycamore. Other non-British records include the bark of more tree species, grass heap, oak faggots, willow leaf litter, and a bracket fungus on pine (Hyman, 1992; Bowestead, 1999). Hyman describes the habitat as ancient broadleaved woodland and pasture woodland, this would accurately describe the remnant habitat explored at Maristow.