|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.
|2 genera, 75 spp. Seventy four species of the large genus Stenus occur
in Britain and most are found near water or in damp situations. A few prefer dry habitats and occur in pitfall traps in open
land and gardens e.g. S.picipes Steph. Examining damp soil between riparian vegetation will usually produce at least a few
species and many can be found sweeping waterside vegetation as they commonly climb plant stems. They are most prolific during the warmer months
but some are to be found throughout the winter under debris, among waterside vegetation or within reed stems.
Stenus species are distinctive with the same appearance irrespective of size and instantly recognisable. The head is broader than the pronotum and this is due to the huge eyes which occupy most of the side. Antennae long and slender, thickened towards apex and inserted on the upper surface of the head near the level of the front margin of the eyes, Prothorax usually elongate and somewhat cylindrical, never bordered. Sides of abdomen sometimes bordered, this is diagnostic to subgeneric level. Legs usually long and thin, adapted to running as anyone collecting these will soon find out.
The majority of the species will key out using Tottenham and Joy from external morphology but the group offers an excellent opportunity to get used to using adaegi as a diagnostic character; they are easily dissected out with a little practice and can be mounted dry, requiring no special techniques. Line drawings are given in Tottenham and Freude (for males) and comparison with these figures is usually straightforward. In some cases, having keyed a specimen to a small group or pair dissection is essential. Females need to be compared or identified by association in difficult cases. After a while dissection becomes routine as one becomes aware of how straightforward identification can become.
For such a large group nomenclature has remained remarkably stable over the years. Several species have been added to the British list since Tottenham's 1954 work and reference should be made, as ever, to the Coleopterist checklist. Hodge and Jones' work gives many useful updates on the list since Joy and Tottenham. Freude Vol.4 deals with over a hundred species so can usually be consulted for additions to our list.
Our single species of Dianous is similar to Stenus. D.coerulescens (Gyll.) has smaller eyes and distinct temples. The last abdominal segment has a pair of long hair like setae. It is large, 6-8mm, deep blue or dark green with an orange spot on each elytron. Several species of Stenus have light elytral spots but otherwise the insects are black without any blue or green sheen, Again, though hardly necessary, the adaegus is distinctive. The species is widespread but local, restricted by its habitat, living in wet moss by running water or around waterfalls.