Several authors of recent books, and lately also able lecturers, have done much to awaken people to a realisation of the dangers of our ever recurrent summer plague of flies. The advent of the petrol motor-car and other automobile vehicles has at the most but very slightly improved the state of affairs within town areas, where mews were formerly much more numerous. The public press has followed suit, but something more in the way of a sustained effort for hygienic reform is desirable. The terrible European war should not preclude consideration of the subject, for the scourges of fly-borne contagion have ever followed armies and rivalled the casualties of the very battlefield. Bands of enthusiasts everywhere should keep going a veritable anti-fly campaign as one of the most urgent needs of practical sanitation. Otherwise active support of the cause will soon languish and be obliterated amongst the multitudinous ever-changing questions of the day, political and other, which, as newspaper editors are persuaded, have the attention of the public for the time being. In spite of the incontestible prospects of universal benefit it may not be easy to engage a large body of public support without something like an organised propagandist movement.

If any readers of this booklet are disposed to join and form a central body with a view of ultimately founding an association for promoting the work of fly extermination, the writer will be glad to find or meet with an honorary secretary and helpers who will work in the cause and economise in the necessary expenditure of all contributions received. After the preliminary efforts of starting such an association, its work will be not only to urge the local sanitary authorities everywhere to adopt the best possible course of action, but also to incessantly move public opinion to compel Parliament to pass laws, capable of administration, for the public welfare in this matter.

The present booklet had its origin very many years ago in the author's idea of writing an account of the house-fly and its kindred, which would be interesting and more truthful than much then to be found in current literature. Such off-hand inconsiderate writing, as appears in the "Elements of Entomology," by W. S. Dallas, F.L.S., requires to be controverted; therein it is stated that the house-fly, which is "troublesome, does very little actual damage, for our only real grounds of complaint are to be summed up in the tickling sensation which its feet cause," &c. "In its larvÆ state, however, it lives inoffensively enough in dung." It has now seemed timely to publish my long-delayed work, re-written with the object of more urgently interesting the general public in the cause of the anti-fly campaign. Still, the author trusts that both the deeper and the less entomologically inclined nature students will find therein not only useful, but also some novel information, given with not too much entomological technicality.

There is no English work sufficiently modern and comprehensive for a study of our native flies. In 1776, Moses Harris, who originated or elaborated the study of wing patterns, published his "Exposition of English Insects," in which more than 300 flies are figured and described; they have the old LinnÆan classification and nomenclature, of course, and the work is scarce. All later attempts by English authors in the way of a more comprehensive student's guide book have been left incomplete. Another excellent, but expensive work, Curtis's "Genera of British Insects," contains about 250 illustrations and descriptions of flies; but most of these are rather rarities, and the amateur in search of a facile guide to the commoner objects of the country-side will be apt to be disappointed. For the sake of readers possibly eager of advancing further in the study, and in the absence of any commendable guide book, a short appendix has been added to the present work, for help in identifying more numerous species and those of many families and genera not mentioned in the foregoing pages. With the leave of the Northumberland, Durham, and Newcastle-upon-Tyne Natural History Society some valuable plates of illustrations are herewith reprinted, and explanatory notes are added, mainly from the volume of the Society's transactions for 1906, a most valuable work and compilation by the late Rev. W. J. Wingate, of Bishop Auckland. This learned entomologist has succeeded in giving a marvellously comprehensive amount of clear condensed guidance. It is a great privilege that the present booklet has been allowed to borrow from such a source of knowledge, valuable far beyond the locality of its authorship.

Other illustrations which have been borrowed appear with the leave of His Majesty's Office of Works, out of Reports to the Local Government on Public Health and Medical Subjects.