|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.
|3 genera 5 spp. Formerly Scaphidiidae, now incorporated into
Staphylinidae on grounds of larval morphology ¹. Atypical staphs but very distinctive form. Two species are large
, >4.5mm.; Scaphium immaculatum Olivier, a rare species from Kent, found in moss, and Scaphidium quadrimaculatum Olivier,
common and widespread, under bark or logs. Scaphisoma species are small <2.0 mm. and associated with fungi or
wood/bark around fungi dyring the winter.
Joy's key usefully covers four of our species, a fifth, the rare Scaphisoma assimile Erichson is covered in Fowler (3:348) and Freude (3;346).
General shape characteristic; very convex above and below, glabrous and very shining. Elytra with well developed sutural striae, truncate at apex exposing 1 or 2 abdominal tergites, the last of which is pointed. Antennae with 5 or 6 terminal segments thickened; symetrical and well developed in Scaphidium, elongate and asymetrical in Scaphisoma, joints 2-6 thin and quadrate or elongate. Basal segment in Scaphisoma long and curved like a small scape. Head narrow, antennae inserted in front of prominent eyes, their insertion visible from above. Pronotum broadened to base with strongly sinuate hind margin which covers the scutellum in Scaphisoma spp. Legs long and thin. Tarsi 5-5-5 with well developed, unmodified claws.
¹ Kasule, 1966. Subfamilies of larvae of Staphylinidae. Trans. Roy. Ent. Soc. 118:261-283