Tachinid Flies by Robert BelshawReview by: Martin C. D. SpeightThe Irish Naturalists' Journal, Vol. 24, No. 10 (Apr., 1994), pp. 424-425Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25539936 .

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424 Ir. Nat. J. Vol. 24 No. 10 1994

to greatly increased levels of recording. Our chief concerns should be to preserve enough examples of what has

been called 'Irish rainforest1 (i.e. raised and blanket bogs) to maintain viable populations of species such as marsh

fritillary and large heath, two butterfly species regarded as declining on a European basis.

On the whole a valuable book which I hope will do much to stimulate future research (including, hopefully, some in Ireland) and similar publications. The chief cavil must be the price which, for a book containing no colour

plates, still seems excessive; perhaps the publishers will take note and bring out a paperback at a greatly reduced

price.

IAN RIPPEY

Tachinid flies by Robert Belshaw. 169 pages. Handbooks for the identification of British insects, 10, 4a(i).

Royal Entomological Society, 41 Queen's Gate, London SW7 5HR. 1993. ?20stg to non-members, ?14stg to

Members and Fellows. (?3stg p&p.) ISBN 0901546 81 X.

For any reasonably sane individual who has had the misfortune to be dependant upon British literature sources

for identification of tachinid flies, publication of Belshaw's revision of the British fauna will come as an intense

relief. Attempting to decipher the almost incomprehensible keys, or peering at the Breugelesque massed ranks of

diminutive illustrations, in the volume the present work replaces, made trying to name even a solitary specimen a

pleasure for only those individuals training for their 'black belt' in mental masochism. But merely to welcome

Belshaw's volume because anything would have been an improvement on its predecessor, however true that may be, is hardly a critical appraisal of Belshaw's efforts! Belshaw's keys are eminently intelligible and most couplets are accompanied by marginal illustrations of features mentioned, helping considerably with interpretation at many

points where this is required. At the back of the Handbook a further 30 pages of illustrations are provided, also

backing up the keys. There are, in total, 440 figures. The illustrations are clear and simple ? rather too simple in

many cases ? and the links between them and the text are not dependent upon a knowledge of complex

morphological terminology. A system of arrows is used to pinpoint features referred to in the keys. A disconcerting characteristic of these illustrations is that the author has omitted from them most features other than those

specifically referred to in the keys. A not atypical result is that the remarkably hairy Servillia species are shown

(Fig. 271) with bald heads, except for a particular patch of short hairs referred to in the key. The non-specialist key user, confronted by the same part of a Servillia under the microscope, could be forgiven for being quite convinced

that he/she has misread the key somewhere, since the hair and bristle-covered object under the microscope bears so

little resemblance to the mostly bald object depicted in the Handbook.

These keys impart the impression that it is now possible to identify any tachinid found in either Britain or

Ireland. But the appalling state of taxonomic literature on tachinids has ensured that these insects have been

neglected, and it is very likely more species remain to be added to the British Isles' list. Twenty more species are

recognized as occurring in Britain by Belshaw than were included in the previous volume, which was published in

1954. This represents an addition of one species every two years to the British fauna in the intervening period. With

the encouragement provided by Belshaw's keys, addition of further species would be expected. But since

Belshaw's keys include only those species already recorded from Britain and make no reference to how many additional species are known in each genus in adjacent parts of continental Europe, or to additional genera known

there, or to relevant literature on potential additions, it could be extremely difficult to recognize the fact that a

specimen is of some species not on the British list, when trying to identify it using Belshaw. This is particularly true

since the male terminalia, usually diagnostic, are figured by Belshaw for only some 25% of the species covered and no reference is made to terminalia figures in other literature for the species not figured by him. The tachinid fauna

of parts of the British Isles other than southern England has not been well studied and the Irish fauna has been

studied least of all. Of the 240 tachinid species known in Britain, Belshaw can confirm the presence of only 54 in

Ireland. In families of Diptera, the minimum percentage of the British fauna which can be expected to occur in

Ireland is 40%, though up to 70% of the British fauna can occur, especially among wetland groups. This suggests that, if the Tachinidae were subject to serious study in Ireland, the number of species recorded here would be

expected to at least double. Further, to judge from the situation in other taxonomic groups, three to five of those

species could be expected to be absent from Britain (and that is excluding species present in both Britain and

Ireland but as yet unrecorded from either island). Anyone seeking to revise the Irish tachinid fauna would thus be

well advised to make as much use as possible of continental literature as part of the operation and not to rely solely upon Belshaw's alluring keys. Sadly, the continental literature is not wonderful either.

Notwithstanding the cautionary comments made in the preceding paragraph, for the "occasional dipterist'' or

the hapless student, faced with the need to identify "a fly, probably a tachinid", Belshaw's volume is extremely useful. He has done the user a great good service by preceding his keys to tachinid genera by a key distinguishing tachinids from related families of calypterate Diptera. This key also clarifies the concept of Tachinidae employed

by the author, who adopts the recent practice of segregating, into separate families, various groups previously consigned to Tachinidae. Thus Oestridae, Rhinophoridae and Sarcophagidae are separated off from Tachinidae

and are not covered in Belshaw's volume. One singularly unfortunate feature incorporated into this key to families

is liable to cause major problems for the non-specialist user, however. And it is only the non-specialist user who would normally have recourse to use the key to families. In couplet 6 the alternatives are subscuteilum large or

subscutellum absent (or no larger than as shown in a figure). The one alternative, subscuteilum large, is figured. The other, subscuteilum absent, is not, and nowhere in the accompanying text is the term subscuteilum defined.

The wording is such as to imply that the subscutellum is a sclerite present in some families but absent in others.

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Ir. Nat. J. Vol. 24 No. 10 1994 425

Only a specialist would know that the term "subscutellum'' is applied only in tachinids, where a sclerite known as

the mediotergite is extremly convex and in its form resembles another adjacent sclerite known as the scutellum. In

calypterates where the mediotergite is not convex and scutellum-like (i.e. in calypterates where in Belshaw's sense

the "subscutellum" is "absent") it is frequently flat, or slightly convex, but nearly always very well developed. How is the non-specialist to interpret this situation? In such specimens the sclerite illustrated by Belshaw as the

subscutellum is clearly present; even if not convex it is certainly not absent. Because this couplet is so badly worded and inadequately illustrated, very large numbers of non-tachinid calypterates are likely to be determined as

tachinids by non-specialists using these keys. Given the general clarity of the English used in Belshaw's keys, this

major error right at the beginning of the identification sequence is extremely unfortunate.

Standard practice, in attempting to identify material of some taxonomic group with which one is not familiar, is to start with a nucleus of specimens reliably identified by someone else, using these reference specimens as an

accompaniment to the identification keys. Anyone attempting to use Belshaw's keys is strongly advised to adopt this practice. There is probably no such thing as a perfect key and assuredly, as more use is made of Belshaw's

keys, more errors and points difficult to interpret will come to light than those alluded to here. But this advice stems

not from discovery that Belshaw's keys are replete with errors ? it is not so much that they don't work ?

generally, they seem to, more or less ? but that he has selected for mention features which are diagnostic at the

expense of features which are obvious. There are some disconcerting consequences of this approach which may be

illustrated by reference to the species Phasia hemiptera Fab. Although this species may be identified satisfactorily

using them, there is nothing in Belshaw's keys to indicate that the male of this insect is, in its appearance, anything more than yet another little grey fly, or that the species shows a truly exceptional degree of sexual dimorphism. With their broad, multicoloured wings and wide, flat, garishly-coloured body, the centimetre-long males of P.

hemiptera, strutting about on the head of an umbellifer, can be one of the most striking and colourful flies of western Europe. The females of the same species lack this dramatic colouration and are rather ordinary looking. Failure to mention such matters is liable to result in any user of Belshaw's keys doubting their determinations, with

P. hemiptera in front of them?especially if they have both male and female specimens. After all, it seems hardly credible that such an exotic creature as the male could be run all the way through a key without any reference there to any of its most outstanding features! If information complementary to the keys had been incorporated into the

species accounts which follow them this difficulty could have been overcome. The species accounts, which take up most of the pages of this identification manual, contain no information of direct use in identifying the species. Instead, they comprise a summary ofthe available information on hosts, habitat, flight period and distribution in

the British Isles. They incorporate references to published sources of data on hosts, but not to the origins of other

data given, or to other taxonomic literature. It must have been a massive undertaking to bring all this biological information together from the scattered literature and it is very nice to see it accompanying an identification

manual. But it seems to have been included at the price of excluding confirmatory morphological information

which is needed, especially in this family of flies, to give the user confidence in the keys. The biological information is unuseable, anyway, by a users uncertain whether their specimens have been named correctly.

Distribution data for Ireland given in this Handbook lists the counties in which each species has been found, based on literature sources and specimens examined in British institutional and private collections, plus material

examined in Irish museums and collections by Peter Chandler, who has probably done more work on Irish

tachinids than anyone else. There appear to be no previously published Irish records of 25% of the species mentioned as occurring in Ireland, so for these species all that is known of them in Ireland is the counties from

which they were collected. In this regard, it is unfortunate that the format precludes provision of complete records or indication of in which collections Irish material of these species is held.

The nomenclature followed by Belshaw is that of Herting's Palaearctic catalogue (1984) and the Check-list of

British species incorporated into the Handbook is absolutely vital for anyone wishing to search for information on

any species whose name they have gleaned from other literature. There have been considerable changes in

nomenclature since the previous (1954) Handbook appeared. Some instances are potentially very confusing, because certain names appear as previously, but, because of reappraisal of the taxa concerned, are now applied to

different species. Care is also needed in respect of sub-generic and generic divisions, there being a number of

genera which have been demoted to sub-genus, subgenera which have been raised to genus and a considerable amount of generic and tribal redefinition which has occurred. Particularly vexacious is the fact that the Check-list is

not indexed. Names of authorities are inexplicably omitted following species names in both keys and species accounts and so have to be searched for in the Check-list. The Check-list is presented in what passes for

phylogenetic order at present, so anyone familiar with previous arrangements could have difficulty locating

species. Human perceptions of tachinid evolution have gone through such contortions in the last quarter century that adherence to the tradition of presenting Check-lists 'phylogenetically' is particularly laughable in the case of

the tachinids and does nothing to help the user ofthe Handbook. The keys to species are unfortunately not indexed,

either, and neither are they referred back to, from the species accounts. So if you know the genus to which a species

belongs but require to check the identity of that species, in order to discover the relevant key, it is necessary to look

up the genus in the index, find the entry for the generic key, go to the generic key and there find the page number of

the key to species for that genus. The alternative is to search through the pages of the Handbook by eye. In addition to the keys with their associated figures, the Check-list and the species accounts, there is a brief

introductory section covering tachinid biology, systematic and general literature and identification. The

bibliography contains some 160 entries. With the exception of eight papers by Herting (in German) these are

almost exclusively to the English-language literature.

MARTIN C. D. SPEIGHT

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