This aleocharine staphylinid was discovered by sieving grass cuttings from Tony Galsworthy’s garden compost heap in Merton Park, Surrey (VC 17), on 13th August 2004 and subsequently. It was first published as an addition to the British list after a specimen was exhibited by Tony Galsworthy and Roger Booth at the 2004 Annual Exhibition of the BENHS (Hodge, 2005). It originates from the Far East and is pretty clearly something that has recently been accidentally imported to Britain and become established. To the best of my knowledge, no further British records have been published but my experience is that this is now a widespread species in south-east England at least and one that is quite likely to be encountered by sieving heaps of woodchip, manure or general garden debris. I’ve recorded it in West Kent, Middlesex, Buckinghamshire and Bedfordshire (VCs 16, 21, 24 and 30), mostly by sieving heaps but also once by evening sweeping on Chilterns chalk grassland. I’m not alone in finding that this beetle has become quite a familiar species.
Derek Lott (2009) briefly discusses how to separate Acrotona pseudotenera from A. convergens, noting that in “A. pseudotenera … the hairs on the mid-line of the pronotum point backwards but the outer margin of each mid-tibia carries a long medial seta”. But the main literature for the identification of A. pseudotenera is Assing (1998) on pages 181 – 182 of volume 15 of Die Kafer Mitteleuropas. Dave Buckingham suggested I should put some photos on my blog, so here they are.
If you have an Acrotona specimen with the 1st hind tarsal segment as long as the 2nd, with a long mid-tibial bristle, and with Pronotal Behaarungstyp V, and it looks like these pictures, it’s probably pseudotenera. The classic Pronotal Behaarungstyp V pattern has hairs on the midline lying backwards throughout but in some pseudotenera, the hairs lie forwards on the front part of the midline, occupying up to 20% of the midline and thus approaching the pattern of Pronotal Behaarungstyp III.
Hodge, P.J. (2005). 2004 Annual Exhibition. Imperial College, London SW7 – 13 November 2004. Coleoptera. British Journal of Entomology and Natural History, 18, 201 – 208.
Lott, D.A. (2009). Acrotona convergens Strand (Staphylinidae) new to Ireland. The Coleopterist, 18, 131 – 138.