There are only three British species in this family and all three seem to breed in the red-rotten heartwood of trees. Like so many of the heartwood saproxylics, it is a rare pleasure to lay eyes on them. They are small beetles (1.5 – 2.5 mm) which I usually see either by beating branches, by aerial interception trapping, by rearing from samples of red-rot, or occasionally by sweeping under and around veteran trees. They are quite distinctive as a family, resembling tiny longhorn beetles though they are not closely related.
The most recent key to the British species is in Buck’s (1954) RES Handbook which is out of print but should be available as a download from here before much longer. But with a little practice, the three species can be recognised in the field.
Vanonus brevicornis is the rarity of the family. Hyman and Parsons (1992) knew of records from just five vice-counties, all in southern England, with post-1970 records from two of those and gave it Vulnerable (RDB2) status. Only about 16 individuals had been recorded in England at that time. It has since been placed on the Burnham Beeches list (Martin Albertini, pers. comm.); a single individual was attracted to light in a Kent garden in 2006 (Chuter, 2008); I caught one in an aerial interception trap on beech at Cliveden, Bucks in 2008 and beat two from a veteran oak at Windsor in 2009; Tom Harrison found one at the base of a beech tree near Abingdon (VC Berkshire) in 2010 (Harrison, 2011). Though there may be other records, this species seems to be retaining its status as an extreme rarity in Britain with perhaps only about 21 individuals ever recorded.
I think the trick for finding Vanonus is to search low down. My Cliveden specimen was from an aerial interception trap set outside a beech rot-hole that was about a foot off the ground. And both my Windsor specimens were beaten from hawthorn branches a few inches off the ground, adjacent to a dead oak.
The species are mostly recorded from early May to mid-September but the peak time for beating Euglenes oculatus at least is from late June to late July.
Buck, F.D. (1954). Coleoptera (Lagriidae, Alleculidae, Tetratomidae, Melandryidae, Salpingidae, Pythidae, Mycteridae, Oedemeridae, Mordellidae, Scraptiidae, Pyrochroidae, Rhipiphoridae, Anthicidae, Aderidae and Meloidae). Handbooks for the identification of British insects, vol. V, part 9. London: Royal Entomological Society.
Chuter, K. (2008). The genus Aderus (Aderidae) in Kent. The Coleopterist, 17, 22.
Harrison, T. (2011). Vanonus brevicornis (Perris) (Aderidae) new to Oxfordshire. The Coleopterist, 20, 81.
Hyman, P.S. (revised Parsons, M.S.) (1992). A review of the scarce and threatened Coleoptera of Great Britain. Part 1. U.K. Nature Conservation: 3. Peterborough: Joint Nature Conservation Committee.