|Staphylinidae Rove Beetles|
| A large family containing more than an quarter of the
British coleoptera. They seem, perhaps understandably, never to have been particularly popular and neither
have they featured usefully in the various guides to beetles that have appeared over the years.
Apart from the most distinctive forms they are difficult, or impossible in many cases, to figure usefully
because there are so many closely similar species and, without an appreciation of the family as a whole and
some very precise guidance, it probably does more harm than good to use such guides for serious
identification. Having said that, colour pictures from general guides (and there are some with excellent anthologies)
can give an idea of the different forms and might also give confidence to an identification made through keys where only
line drawings have been used. It must also be mentioned that, for somebody interested in Coleoptera but approaching
staphs for the first time, they might seem drab and even tedious e.g. having seived an autumn fungi or dung sample
and obtained a few hundred staphs less than 2mm in length, and a good number of them half this length, one needs a certain resolve
in the aspects of dealing them that follow
What follows is our humble effort to help make staphs more accesible. In order to partition the family into maneagable groups, subfamilies and sometimes lower divisions are considered individually.There are many distinctive forms which, when they are learned and (mentally) removed from the list, leave the remainder much easier to appreciate. Notwithstanding this it soon becomes obvious that the problems involved with identification are formidable, and the situation is compounded by there being no comprehensive keys available in English.
At this stage, i.e. early in ones study of the staphs, it is worthwhile learning enough German to be able to make sense of the works of Freude et al ¹, these books give only line drawings but they are lucid and somehow easy to use, they do not repeat the mistake of Joy's Handbook ² where line drawings are proportional to a species size so that the smallest figures, which might have been most useful, become almost useless without a great deal of experience.
Admittedly one needs to be single minded and very determined with the staphs, they are difficult, but every successful identification provides material that can help guide other specimens through the keys. Studying staphs will soon generate a considerable number of identified specimens but in each case they should be taken as far as possible and then labelled and listed for future reference. This will be frustrating but also worthwhile, the secret is to keep on trying to key things out and remain aware of how far your unidentified specimens go, sooner or later things begin to fall into place.
This situation is unfortunate because for those interested in or even (as, sadly, with one of our group ³) excited by dealing with microscopic rove beetles the amount of work needed is very considerable.
Almost, it seems, by way of compensation the syaphs are not difficult to collect. They are found in most situations at most times of the year and just about any collecting technique will produce them. Samples of almost anything organic (sometimes even seaweed) will probably contain at least some; sweeping, beating, light trapping, ?? netting, pit fall trapping etc. etc. will produce them. It would be far easier to list situations where they are not found. Some idea of the ecology of the group is given under the subfamily and species descriptions.
¹ Die Kafer Mitteleuropas, Freude, Harde, Lohse. Vols 4 and 5
² Practical handbook of British beetles, Joy
³ The author's son, one of our junior members, continually provides copious amounts of specimens which the father is expected to set, mount and identify - Webmaster.
| <1-35mm. Generally elongate with short or medium length
elytra leaving at least part of the abdomen visible, in some species of Omaliinae
this may not be obvious. Sutural stria of elytra usually straight but may be modified and overlap e.g.
or Xantholinus spp.. Abdomen eight segmented and usually flexible, variously covered by elytra, terminal
segments may telescope in so care must be taken to appreciate this. Any serious study will necesitate dissection,
the male and female genitalia are often distinctive. Head from broadly transverse to elongate with temples varying
from dilated to contracted to non-existent, sometimes withdrawn into prothorax. Eyes variable but usually entire,
perhaps best developed in Stenus spp., ocelli present in
Omaliinae and Proteininae. Antennae
usually 11 segmented, sometimes 9 or 10, and variable from filiform to broadly thickened or clubbed and variously setose.
Their position of insertion provides the basis of a practical guide to subfamilies. Thorax and abdomen are
variable, from cylindrical to arched or flat, variously sculptured and modified e.g. Omalium,
and Bledius. Legs are generally less variable than other characters; mostly long and/or agile, many species
are capable of rapid movement when disturbed e.g. Ontholestes or Creophilus. Despite the lifestyle of many of the
staphs i.e. burrowing in fungi, dung, carrion etc. the fossorial leg structure of, say, Clivina
or Aphodius is
rarely developed. Tarsi 3,4 or 5 segmented many combinations, it will be useful or even essential to be able to count these (ID Aids)
but this presents a great obstacle in tiny Aleocharinae species, so much so that both Freude and Joy provide practical
help to this group as well as help based on tarsal formulae. Those without experience will find the ID notes useful.
Part of the reason for presenting this site is to show people some of the Coleoptera of our area while providing guidance as to how to make identifications certain. In some groups of staphs this is very difficult and, for this reason, the Aleocharinae are left out of the following discussion covering subfamilies. Apart from this the sequence follows that of the checklist from the Coleopterists website which represents, we trust, the latest ideas in staph phylogeny. In this list the former families Psephalidae and Scaphidiidae are treated as subfamilies of the Staphylinidae and so are considered here. Aleocharinae, which require a rather more detailed approach, will be considered separately following the subfamily discussions.
|19 genera, 53 spp. These are very distinctive species of two
general forms; broad e.g. Bryaxis, and the more typically staphylinid linear form e.g. Euplectus.
The two species of Claviger are unusual and, for convenience, not included in the subfamily description that follows. They are small, 2-3mm., with tiny eyes and six segmented (four visible) antennae. A large depression (trichome, a licking spot, an adaptation for living with ants) occupies the (apparent) first abdominal tergite. They are found exclusively in ants nests.
Antennae 11 segmented, apically thickened and with a distinctive terminal club. Inserted above mandibles, basal segments obvious. Terminal segment of maxillary palpi longer than others, often highly modified. Tarsi 3 segmented. the first often tiny, and with a single claw (in all British species) but in some (Batrisodes, Tychus there is also a stout seta which can be mistaken for a second claw. Upper surface with deep wide fovea, often between eyes, on pronotum, elytra or on sides of metasternum. Many species are pubescent.
So far as identification is concerned these can offer formidable problems, e.g. Euplechus spp. and Biblioplechus spp. where careful dissection is necessary and females can only be determined by comparison or association. Among the staphylinidae as a whole, however they are not likely to be confused with any other subfamily and will soon be recognised instantly when sorting through samples.
Collecting these is not easy, we have specimens from grass tussocks, moss and bark from a wide variety of habitats but it must be said that they turn up at random, taking samples specifically to find them can be very frustrating. Berlese extraction is probably best, if time consuming, as one needs to be very diligent and patient if working samples under spotlights; the few we have found by this method have remained stationary for a long time.
They are associated with bark and rotten wood, moss, leaf litter, plant tussocks (often from riparian areas), manure heaps and hot beds, in general shaded and moist habitats. Euplectus falsus Bed. has been found in bird's nests. Brachygluta spp. are found only in salt marshes. Many species are associated with ants nests and their surroundings, some are strictly myrmecophilous: Claviger spp., Amauronyx, Bythinopsis and Batrisodes spp.
Unfortunately many of our species are rare or very local but by searching carefully and patiently one can confidentally expect to find half a dozen or so fairly quickly. They should be looked for year round.
Joy's keys must be considered out of date, and while Pearce's (1957) treatment omits 5 species now on the British list, it is a very good introduction to the subfamily. Besuchet's treatment in Vol 5 (updated 1989) of Die Kafer Mitteleuropas is elegant and well worth the effort involved in its use, the line drawings of insects and aedeagi are very good (see page 339!).