We include this article in the identification aids for the obvious reason that it might be useful when looking at these
insects but it was originally written as part of the work on identification in our techniques section. There are many groups
of British beetles that are very difficult to deal with for a variety of reasons; they might simply be small and so daunting
to the beginner, they may not be straightforwardly covered by literature printed in English e.g. the latest checklist may
contain species not covered by the most widely available key which in many cases will be Joy although the earlier RES
handbooks are nowadays suffering the same kind of redundency, or in many cases, a specimen simply will not go through a key
with confidence. Without familiarity many of the smaller staphs fall into this catagory and it does not help the situation
having Joy's key as the only option for many of the groups. So we have chosen Autalia as a brief case study into some
of the problems likely to be encountered when dealing with these tiny staphs; from the outset it must be admitted that the
genus is for many reasons an easy option and hopefully this will soon be realised be the reader, but this is part of our
intention i.e. to promote the idea that these small and nondescript looking things can in many cases be dealt with and
confident, satisfying and useful results obtained. Among our reasons for choosing Autalia are the following:
Three species are included in Joy's key and two of these may still be identified with confidence. Couplet 1(2) separates A.impressa Ol. on colour, it is bicoloured reddish and black.The other half of the couplet separates off A.rivularis Gr. and A.puncticollis Shp. : 2(1) 'Black, el sometimes lighter' and here there is (presumeably) no scope for confusion. Lohse splits the genus similarly as does Palm (1968 p.67.) Separation of these black species is straightforward and Joy gives firstly a purely subjective character: 'Th. microscopically diffusely punctured' for A.rivularis Gr. or 'Th.distinctly rather closely punctured' for A.puncticollis Shp. and this kind of couplet can be completely meaningless when only one specimen is available. On the other hand his following character is less ambiguous: (pronotal) central furrow deep, extending to transverse furrow at base' for A.rivularis Gr. and 'central furrow shallow, visible only in front' for A.puncticollis Shp. The size ranges given for these species may be useful as a guide with larger and smaller specimens; A.rivularis Gr., 1.5-2mm and A.puncticollis Shp., 2-2.5mm. A little more confidence is gained from Lohse, who gives 1.7-2.1mm and 2.1-2.6mm respectively. A little more on these species later.
In 1947 Dr Otto Sheerpeltz (1947) published a description of another species, A.longicornis, which is close to A.impressa Ol. and had up until that time been included with it, thus Joy's first couplet became useful only in separating off the 'black' species. In his paper Dr Sheerpeltz describes in meticulous detail some subtle morphological differences between the two species and provided convincing line drawings of the forebody of each.These differences concern the antennae;longer and more slender in A.longicornis, the smaller but more prominent eyes of A.longicornis, differences in head shape, pronotal shape and elytral shape and pubescence. These descriptions are very convincing and one is left in no doubt that typical specimens will be confidently assigned. Following this detailed description a key to the palearctic species is given which, in the first couplet, separates the 'black' species on pronotal sculpture as in Joy's key. A.impressa Ol. and A.longicornis are then separated initially on antennal structure: fourth joint quadrate (our words)...A.impressa Ol. or fourth joint 1.5x longer than broad...A.longicornis sp.n. Following the antennal description he then discusses the other characters.
With such fine line drawings and descrpitions one would imagine that the species have diverged sufficiently to allow identification on external morphology alone and, obviously, in many cases they have become so; were this not the case Dr Sheeerpeltz would not have realised the difference and the split would not have been possible! But it must constantly be bourne in mind that with coleoptera things are rarely so straightforward.
When, in 1974, Dr Lohse produced his key to aleocharine staphs in volume five of Die Kafer Mitteleuropas he keyed Autalia on external morphology and gave similar, if not quite so convincing, line drawings of the forebody of the 'bicoloured' species. Which is to say that to those unfamiliar with the genus this reinforces the notion that they will be adequately separated on morphology. Palm's (1968) key deals with our four species, separating firstly on colour and then, again, for the 'bicoloured' species initially on antennal, and here he gives a large and clear line drawing of the basal segments showing the generally more elongate nature of the segments in A.longicornis Scheerpeltz. Beyond a finely detailed whole insect drawing of A.impressa Ol. (p.65) no other drawings are provided and there is no further reliance on external morphology to separate the species. He does, however, provide (p.74) a basic but perfectly adequate line drawing of the penis of each of these species and the difference is immediately obvious. This is not the first time the male genitalia have been featured for line drawings were given by Hansen (1954) fourteen years before Palm's work and twenty years before Lohse! Further evidence that external morphology is adequate for their separation?
A discussion of some morphological features which may be used to separate these species is given by Owen (1984) and includes colour; in A.longicornis Scheerpeltz the elytra are darker than the pronotum wheras in A.impressa Ol. the pronotum, apart from the base which is lighter, is almost as dark as the elytra, punturation which in A.longicornis Scheerpeltz is extremely fine so that the surface has a shiny appearance whereas it is larger and somewhat papillate giving it an overall duller appearance, pronotal grooves which are deeper and more parallel in A.impressa Ol., abdominal puncturation is also mentioned and the last few tergites are shiny but have a shallow reticulation in A.impressa Ol. which is not visible in A.longicornis Scheerpeltz. He then points out that some features previously discussed i.e. form of the antennae and head shape exhibit too much overlap to be 'consistently useful.' Without experience or reference material and faced with a single specimen the doubts must now creep in; reading descriptions of subtle differences will often give a feeling of great confidence but experience will soon show how difficult such things can be to appreciate in real specimens! A great deal of time and effort may be spent deciding to which species a specimen belongs and in cases such as this, whether dealing with a single specimen or a series, there may well be less than absolute certainty over the identification. On the other hand Owen very usefully provides good line drawings of both the aedeagus and the spermatheca of each 'bicoloured' species so that, if one is prepared to dissect, a certain identification can be made every time and morphological considerations can largely be ignored. Upon obtaining Owens paper our own series of 'coloured' Autalia , provisionally split into two groups and stored under two specific labels, all proved to be A.longicornis Scheerpeltz.
In this brief discussion we have tried to show that by following up references it may be possible to assign specimens with absolute confidence; our example is a simple one and was chosen because it shows how a complete genus has been investigated satisfactorily. Dissecting specimens is absolutely essential in this and many other cases and we intend to show dissections and how they are diagnostic. That is not to say that these methods will always solve identification problems e.g. there are a few groups where, even with the help of genitalia figures, definite identifications are not possible from the amateur perspective because reference material or experience may be essential but on the other hand there will be very many cases where reference to figures in foreign works will solve problems.
In A.impressa Ol. the apex of the aedeagus is straight while in A.longicornis Scheerpeltz it is bent downwards.
The 'head' of the spermatheca is narrow relative to the 'stalk' in A.impressa and the coils are more extensive and thicker. The coils will often be disturbed in dissection and may lie in any orientation to the stalk but the base of the stalk is constant; tapering and angled in A.impressa and truncate with the coils originating laterally in A.longicornis.
Scheerpeltz, O. 1947. A British and continental species of Autalia Mannerh. (Col., Staphylinidae) new to science, with a key to palaearctic species of the genus. Entomologist's Monthly Magazine 83: 104-107.
Hansen, V., 1954. Rovbiller 3. Del (Staphylinidae 3. Teil). Danmarks Fauna 59, kobenhaven, 499pp.
Palm, T.1968. Svensk Insektfauna 9(5):68.
Lohse, G.A. 1974. In Freude, H. et al. Die Kafer Mitteleuropas 5:64.
Owen, J.A. 1984 A note on Autalia longicornis Scheerpeltz (Col., Staphylinidae) in Britain. Entomologist's Monthly Magazine 120: 223-225.