With the present day zeal for popularising interest in common things (called nature study) there has arisen the demand for knowledge practically useful and thoroughly up-to-date, yet in a form free from much of the technical terminology and treatment which are essential in the student's more fully developed scientific handbook.

The "House-fly" is a fit subject for a simplified study of this kind, and the present booklet is an attempt to afford information very different to that of the "popular" works, which only were accessible to the writer's hands between fifty and sixty years ago; the writers of those old books all followed the lead of the reverend and learned contributors to the famous and monumental "Bridgwater Treatises." "The Wonders of Nature explained," "Humble Creatures" (a study of the earth-worm and the house-fly, in popularised language), "The Treasury of Knowledge," "Simple Lessons for Home Use," were the kind of cheaper works in touch with a past generation; these latter and other later well-intended publications will now be found to be somewhat deficient or even a little misleading entomologically; they abounded in pious sentimentality and mostly attempted an aggravatingly grandiose literary style, but all have rather failed in teaching practical economic utility, in connection with which nature-knowledge can be rendered as interesting as any other kind of instructive literature. The tribe of two-winged flies, in particular, has not even yet received a full and adequate study by scientists. A preference has ever been shown towards those other branches of entomology, which may be more interesting to the cabinet-specimen collector, but which cannot pretend to have an equal hygienic and economic importance to humanity.

The presence of the house-fly in our dwellings is often submitted to as an irritating but an inevitable nuisance; yet very certain remedial measures would almost exterminate the creature, which is a dangerous and filthy peril. To many people it will seem a most incredible exaggeration when told that it is really worse than any one of the less common creatures universally regarded with horror and disgust as pestiferous vermin. The surmise may be true that the disgusting body louse carried bacteria, which spread the "black death"; and, even though the rat's flea has been found to be the carrier transmitting bubonic plague, yet amongst people living now in civilised communities within the temperate zones these parasites cannot be ranked as dangerous equally with the house-fly. The modern crusade against the house-fly is not based on any such new discovery, as is that against the mosquito gnats, which are the means of spreading zymotic diseases mainly in the tropics. The malignity of the fly is recorded in most ancient history and folk-lore, yet not very long ago there prevailed amongst certain classes opinions very different to those of old as well as to those of the present day. A short anecdote will perhaps amuse as well as explain those misplaced sentiments, which have not quite died out.

In the middle of the last century there was a boy, thought to be too delicate to be sent to school, who early earned for himself the character of being a strange child. When barely more than nine years old he visited an Aunt who was a veritable exemplar of genteel breeding and propriety after the early Victorian pattern. There he was seriously reprimanded for the "cruelty" of feeding his secret pets, which were garden spiders, with flies which were, so the Aunt said, "poor innocent creatures made by God for a useful purpose," but, she inconsequentially added,-"Spiders were horrid." The strange child replied that the Devil made the flies, and that God made the spiders to eat them. The astonished Aunt then elicited the fact that the strange child's father had explained, during a Sunday Bible lesson, that Beelzebub (the Devil) meant Lord-of-flies.

This strange child was taken a walk over Doncaster Heath by the Aunt's maid. There a dead rabbit was seen from which maggots were crawling, and the maid explained that it was fly-blown. Next they both stroked and patted a patient donkey, and the strange child observed maggots rolling out of the donkey's nostril[1] on to the ground; he wondered much that live animals should be fly-blown. He also saw with pity some cows, around whose eyes flies clustered.

Pondering on these matters, one day he confided to the Aunt his confirmed opinion in these words-"It seems, Aunt, to me that people who won't kill flies deserve to be fly-blown." Doubtless, it would have been better if he had expressed himself thus-People who will not kill fleas deserve to be flea-bitten; and people who will not wage war against flies deserve to be fly-tormented. However, the horrified Aunt mistook the observation for insult and impudent rebellion, and what ensued need not be related as pointing no useful moral. The strange child was merely a genuine early nature student ahead of the times by some fifty or sixty years. In due course he learnt a more orthodox account of "Creation," and the existence of mysteries in facts physiological and spiritual, which can only be imperfectly comprehended in this world.

His craving for nature study was not satisfied with the reading of most of the cheap books then published for the diffusion of knowledge. Collecting butterflies and moths sufficed for some of his schoolfellows in later years, but, not then having access to really good handbooks, he became an original investigator in wide fields of nature study, and thus learnt that many statements and opinions, which ordinarily even at the present day pass current as facts, are erroneous and misleading. Accordingly, the reader need not be surprised at some statements in the following pages at variance with what may be met with elsewhere.

1. Stevens' Book of the Farm and many other publications describe the similar affliction of sheep by Œstrus ovis but omit to notice the case of the donkey, which I have witnessed several times, but have never seen a horse or pony thus afflicted. There is a fly termed Œstrus nasalis, of which the victimised host is uncertain, for Linnæus was mistaken in stating that the larvæ are found in the fauces of "horses, asses, mules, stags, and goats," entering by the nostril.

The old fanciful dogma that everything existing was actually created "in the beginning," and "for a purpose," was once ardently championed as controverting aggressive Voltairean atheism, but it must be now recognised as an unwarranted assumption, deduced from an orthodox doctrine of "design," which in itself seems acceptably agreeable with the idea of unity, consistency, and perfection in Creation and The Creator. In fact the said "fanciful" dogma never really was an integral part of Christian Catholic doctrine. The house-fly, as we know it, is absolutely the developed product of human insanitation; scientifically and practically it is a new "species" of an old "genus" established by a long course of breeding in man-made environments.