29 APRIL 1893, Page 10

An Account of British Flies (" Diptera"). By Fred. V.

Theobald, B.A., F.E.S. Vol. I. (Elliot Stock.)—It is not many years since British entomologists spoke of five out of the seven great orders of insects as "the neglected orders," at which no one worked, and about which no adequate or trustworthy information could be obtained,—at least, in English. Nowadays, more students are beginning to interest themselves in other insects besides beetles, butterflies, and moths ; but the gaps in our knowledge of British entomology are still very wide ; and one of the largest and least- known orders of insects is that of the Diptera, or Two-winged Flies. Little has been published to elucidate this order in England since 1856, when Walker completed his useful but rather uncritical and unsatisfactory work in three volumes, in the series called "Insecta Britannica ; " but this work is now scarce and out of date. Hence Mr. Theobald has rendered good service to beginners who wish to take up the study of this little-known order, by commencing an un- pretentious work containing a large amount of useful information, and illustrated with four plates and numerous woodcuts. The pre- sent volume contains the characters of the 49 families into which the author divides the Diptera; chapters on "Fossil Diptera," and on the "Classification of Diptera" (the latter of which appears to us less complete, at least as regards recent authors, than it might have been) ; and a brief account of the principal British species be- longing to the first six families : Aphaniptera (Fleas), Ceeidomyida (Gall-Gnats), Myeetophilida (Fungus-Gnats), Bibionide (St. Mark's and St. John's Flies, &c.), Simuiiider (Sand-flies), and Chironomidce (Midges). The author says in his preface : " In a small work of this kind, it is impossible to give a detailed description of all the species recorded as British. I have therefore chosen those about which there seems no doubt, and have omitted many mentioned by Walker as being doubtful. The families treated of in this volume are the most difficult and least understood of any, and are in a most unsatisfactory state with regard to their systematic arrangement and identification." Until we have ascertained what species are really found in Britain, and until their identification is accurately fixed, a satisfactory monograph is out of the question, and we think that Mr. Theobald has acted very wisely in not attempting to produce more than a useful introductory book at present.