Identification

Even when considering our limited U.K. fauna this can be a very difficult subject for the beginner to master because of the range of variation in the morphology of our various families and genera, not to mention the species themselves e.g. Abax parallelopipedus will be readily recognized by an experienced worker, but without this experience it could look very much like Pterostichus niger, and without pictures and guidance there may be other genera to which it might belong. To the experienced coleopterist the form of the elytral and pronotal morphology is absolutely distinctive and anyway, even without having to consider these features, it just looks unmistakably like Abax, and nothing else looks like Abax so that’s what it is. On several occasions in the field Conall has seen a Carabid running after we have lifted a log or while we are examining reed-litter and said ‘there’s Abax, or there’s Paranchus’, or whatever, and usually he is correct, much to my annoyance as my eyesight is not what it was. Harpalus rufipes is similarly distinctive, and to anybody familiar with our Carabidae many of our species will similarly be quickly placed, at least into the correct genus and very often into the correct species, even in the field. This ability comes from an innate passion for the subject and the nature of this expertise is a familiarity acquired through experience; this is simply the result of spending a few hours, or days, or years or decades looking at beetles.

Abax parallelopipedus (left) and Pterostichus niger (right)

Two similar species, easily recognized with experience.

But there are various ways of looking at beetles. There is no doubt that a reasonable familiarity with our fauna can be gained from browsing through books with good colour plates, and this behaviour will allow many families and genera to become recognizable; if enough pictures are examined carefully, and with a reasonable amount of reading about how the various species are adapted to their environment, it is surprising just how many species can be named, or at least placed into their correct groupings, and when we turn to unfamiliar publications or pictures on the internet we find that many of the beetles are known to us, at least to some extent. In this way many U.K. species can be placed with absolute confidence e.g. Lucanids, Pyrochroids, some Cerambycids, Carabids and Staphylinids etc. And some further species, following a little research, can also be placed quite quickly e.g. water beetles are a very distinctive group i.e. boat-shaped and drab with tapering legs and filiform antennae, and so when pond-dipping they will be obvious among the other stuff, a species like Colymbetes fuscus can be compared with pictures and when it ‘looks about right’ a reference to a description, noting the size and characteristic elytral microsculpture, will give the correct name with confidence. This system of comparing a specimen with pictures and then referring to a description will work with many species e.g. Chlaenius vestitus, Thanasimus formicarius, Platystomus albinus etc. In theory at least all our species could be similarly placed, given enough pictures and descriptions any specimen can be narrowed down to the correct species. Once familiar with the various groups this is how all coleopterists work, but with such experience all the groups are familiar anyway and the use of pictures is, generally, no longer necessary.

Water Beetle reference collection, arranged systematically. 

When beginning to study beetles most people will need to build up a collection, or as such things are usually referred to, and with very good reason, a reference collection. Each named specimen added to this collection will represent a part of the fauna with which the collector is now familiar and it will allow further specimens to be identified by comparison and it will allow others to be eliminated from various groups. Such a collection will also allow a range of variation to be displayed e.g. in ladybirds. This is why some data labels bear the words ‘by comp’ i.e. because this is how they have been identified. But there will come a time when a large number of accumulated unidentified specimens need to be dealt with i.e. named, and this generally happens when those that can be dealt with by comparison etc. have all been added to the collection under appropriate labels. At this point the use of ‘keys’ will need to be mastered. It will soon be explained why the above method of placement is so very important but for now mastering the use of keys is vital. Keys are available at all levels of classification-the grouping of species into genera or families or super-families etc.- but in some sense they should be used only as a last resort. Take e.g. the need to use a  key  to  determine  the  family

placement of an unfamiliar specimen; so far as we are aware there is only one modern key that will do this, that by Unwin, adapted and used by Andrew Duff in the first volume of his Beetles of Britain and Ireland. This key is very difficult to use even with experience; with the best of intentions it is to be avoided if possible (the way tarsal formulas are used is sometimes baffling to us), with a great deal of care and patience it will work but for many ‘obscure’ species-and these are the most likely to be put through this key-it will need to be used alongside google or a similar source of good pictures so that likely suspects can be confirmed. But it is the very time consuming nature of this process that is important to us here; when sampling in the field a good day may produce hundreds of specimens, although this will be reduced as familiarity is gained and many species can simply be noted down rather than collected, and if trapping techniques are used this number may be in the thousands, and so it is vital that short cuts to identification are found; it is all very well going back to a difficult specimen a few times and trying the keys again to see if you have any luck, but if boxes and boxes of specimens are left to be assigned it becomes soul-destroying to see the work accumulate without, or with only very slow, progress. Admittedly when a key is used frequently the various couplets become familiar, and after a decade or two most of them do, but with unknown specimens each and every couplet must be worked thoroughly and pictures and descriptions consulted. Curiously, a key to the families was produced by Joy in his handbook of 1932, and this rather simplistic arrangement just seems to work with very little fuss, it is accompanied only by line-drawings but it seems to have some sort of natural logic that works for the majority of species, but unfortunately with so many additions to our fauna since its publication it is now generally out of date. But Joy’s family key is still very useful and it remains an important work, more especially so as the keys are of a rather simple and straightforward nature and so will readily be appreciated-at least by the beginner- and the results can easily be checked using modern works.

Another family key was produced by Roy Crowson as a Royal Entomological Society Handbook in 1956 (many of which, including this one, are available online), this is very technical and difficult to use, certainly for the beginner at any rate, but it contains a wealth of information on morphology as well as a few very impressive habitas drawings and so is a very good source of information. And so to circumvent the use of family keys, and so avoid a great deal of time-wasting and frustration, it is vital to place the majority of specimens quickly by comparison. Once a family has been assigned it is generally much easier going to place a specimen, especially so when it is in one of the more popular families e.g. water beetles, ground beetles, longhorns, leaf beetles or weevils etc. Keys work by offering a cascade of alternatives; at each point a specimen is assigned to a couplet which will lead either to another couplet or terminate in an identification, and when the process is finished the specimen can then be checked by other means e.g. by reference to a description or to a picture, preferably both. It is sometimes the case that two species may be closely similar-sibling species-in terms of how the key is written, but here the reference collection comes in useful as one or both alternatives may be available for study, and it is very often the case that when the actual specimens are examined the differences become obvious in a way that defies description in a key e.g. with species of Crepidodera or the ground beetles Carabus violaceus and C. problematicus, with experience these two Carabids become instantly recognizable in the field. Keys can work on purely morphological grounds i.e. by using the most obvious characters with which to separate the species or groups, or they can reflect the differences of the groups in a phylogenetic sense by working through the species from the most primitive to the most advanced in evolutionary terms. This last aspect demonstrates another aspect of keys; as well as being purely functional i.e. as tools for determination, they can also teach us a great deal about the evolution and adaptations or specializations of the various groups; Joy’s keys perform practically while Andy  Duff’s  keys perform in  a phylogenetic  sense as  well as  practically, and keys  are

Joy's 1932 Handbook

easy to read when compared to slabs of text which can become tiring or confusing when trying to keep up with evolutionary systems. As keys are worked through, especially relatively large keys like Hydroporus, Cryptophagus or Longitarsus, it becomes obvious that the morphological differences, at least generally, become ever more subtle; distinctive species tend to be dealt with early on in keys in order to eliminate them from the more involved and morphologically similar groups, and sometimes very comparative features may be used e.g. the ratio of lengths of antennal segments, or underside characters may be employed that seem to be a pain to use if dealing with nicely set specimens glued onto cards e.g. punctation on the underside of some Perapion or Pterostichus, or subtle differences in the extent of sutures in some ladybirds or the form of the prosternal process in Haliplus species, but soaking a specimen off the card and examining the underside is a small price to pay for an accurate identification, not to mention the great deal of satisfaction achieved.

But there comes a point where external morphology is insufficient to differentiate species and here we must accept that a correct determination depends upon dissecting a specimen and comparing various internal structures, generally the genitalia, with figures given in keys. These structures are often, but by no means always, species specific and so will allow many doubtful specimens to be placed with confidence, some genera can only be dealt with by using this method e.g. Altica, Longitarsus, Ophonus and many Staphylinids, although having written this it is often the case that further specimens can be placed by comparing them with dissected material.  The procedures involved in dissecting can seem daunting for the beginner but it only takes a few hours with ‘spare’ material to start to produce results, and after little experience a natural hand control and a degree of ambidexterity seem to develop without really trying. We hope to add a section about dissecting later on but for now it is important to understand that certain aspects of morphology need to be appreciated in order to achieve good results e.g. structural morphology in general-the names of the various sclerites will need to become second-nature-microsculpture, the placement of sensory setae and the often subtle form of elytral striae etc. This may seem like a lot of learning but most of it sinks in naturally when doing practical stuff like identification. Counting tarsal segments is a very important procedure e.g. it will immediately distinguish Oedemerids from Cerambycids, and while all coleopterists know that a 5-5-4 tarsal formula will probably indicate a member of the Tenebrionoidea the beginner may neglect this and so spend a delightful few hours trying to place Nalassus in a key for Amara. Even when dissected the females of some species cannot be placed with certainty and so it is generally important to organize the specimens from a particular outing according to where they were found, under what conditions, and what specimens were found together as this may allow some females to be assigned by association. Finding a mating pair is even better as not only does it demonstrate both sexes of a particular species but also provides some information about the biology of the species i.e. at what time of the year and under what conditions they breed. For the same reason it is a good habit to write down the host plant, or at least the plant on which a specimen was found, in this way Galerucella nymphaea can be named with confidence if it was found on water-lilies as the sibling species G. sagittariae occurs on Rumex as well as some other plants but not on water-lilies.

Ultimately, when it comes to learning about identification, there is one method that beats all others hands-down and will provide a truly invaluable source of information. Get out into the field with an experienced coleopterist, listen as they use the names, appreciate how they home in on likely habitats, and ask how they are able to rattle-off lists of names as though they are reading from a checklist. It can be a humbling experience but will be worth every second.

This section will be used to present keys to some of the groups we discuss on this site; these will, rather obviously, be a synthesis of knowledge used in other keys but in many cases we have used the couplets and are aware, from our reference collection, of the characters we choose to use and so in some sense we write from experience as well as from the literature. Regarding the U.K fauna we are very fortunate to have a wealth of literature available written in English and we hope to feature some of this in the library section as we develop the site.

In order to understand the process of identification it helps to appreciate the fundamental divisions of the order, at least as it applies to the British list. We are not going to provide a definition of the order as it is assumed that anybody surviving the text thus far will be sufficiently aware of what a beetle is, at least in the obvious sense, to render this unnecessary. Having written that I did have the strange experience once of looking at a ‘weird’ staphylinid for a friend who had lost patience trying to identify it; it was an immature earwig.

Anyway...

Family Keys

 

Subfamily Keys

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