Bearing a strong resemblance to the bluebottle fly is the gre bottle fly, which is slightly smaller and metallic green in color. is commonly found near putrefying flesh, such as dead animals, creta, and similar filth. A member of this family often breeds the excrement on the backs of sheep, the larvæ or maggots devel ing and feeding thereon, resulting in a serious pest to flockown When the larvæ mature in either filth or flesh they are especia voracious and consume a large part of the substance on which t are developing. The fact that insects of this family alternate tween human excreta and food products renders them especially d gerous, although their number is usually limited and they are dom satisfied to remain within doors.

One of the most important species is the stable fly, or, as i sometimes called, the "biting stable fly." It is less often found filth than the other varieties, but owing to the fact that it is a blo sucking fly, opportunity for the direct inoculation of persons animals with the organisms of disease is presented. It is this sect which has been incriminated in the spread of anthrax. stable fly is about the size of the common house fly and resem it in appearance, being gray in color and somewhat more sto built. Its proboscis, however, is of an entirely different charac as campers and others can testify, being arranged for penetrat and sucking. It frequently torments horses and cattle and may e cause detriment to stock through its activities. The insect is wi distributed. Closely allied to the stable fly is an African spe known as the tsetse fly, which is responsible for the spread of sle ing sickness, a fatal infection found in certain regions of the Afri Continent.

The "lesser house fly" is the name given to a species which, 1 to the house fly, is the most common indoor resident. Proba everyone has observed the useless and apparently aimless, jerky fli of this insect beneath some suspended article, such as a chande This fly is an early visitor, usually being found before the com house fly is present in large numbers. Its breeding habits are same as those of the house fly, but as it feeds less diligently seldom alights, it is somewhat less objectionable. It strongly res bles the house fly but is slightly smaller and more slender, be perhaps, better adapted to flight. The larval form of this fly easily distinguished from that of the common house fly, as it is ered with spines.

In addition to the species enumerated, many other bloodsuck and nonbloodsucking varieties are of interest. The cheese fly posits its eggs in cheese or fatty material, producing the so-ca cheese skippers. The dung and the yellow dung flies and the lat fly are so named because they develop in the excrement of anin

or man. The fruit fly, a much smaller species than any of those mentioned, hovers about fruit juices, cider barrels, and like situations, being often found in the dregs of wine. None of these species, however, is as important as the common house fly.

Structure.

The parts of the fly are the head, thorax, and abdomen. The head is connected with the thorax by a narrow neck which permits of rather wide movement. The greater part of the head is occupied by the eyes, some several thousand in number, described as compound. Between the compound eyes and near the top of the head is a triangular arrangement of three simple eyes. The upper two are much farther apart in the female than in the male, thus serving to easily differentiate the sexes. In spite of the arrangement of the eyes and the great mobility of the head, it is not believed that the vision of flies is especially acute, although the range of vision is wide. The sense of smell, however, is highly developed.

The proboscis protruding from the under and back part of the head is the most interesting part of the fly. When the insect is at rest, the proboscis is folded against the head, but upon alighting it is protruded through the mechanical action of certain air sacs. Capping the end of the proboscis are two oval projections or lobes forming an opening leading into the mouth. The oral lobes in the house fly entirely prevent penetration of the skin by the proboscis, therefore this particular species is in no sense a biting fly. Biting invariably constitutes positive proof that the insect is not a house fly, however much it may resemble that species. On the under and inner side of the oral lobes are grooved channels which lead into the mouth. When these channel-like surfaces are placed in contact with liquids, suction is performed by the pharynx and the substance is drawn into the œsophagus, to be continued through the narrow neck into the thorax. If the food is solid it must first be dissolved through the action of saliva secreted by the salivary glands or reduced to very minute particles.

The greater part of the thorax is occupied by the muscles used in flying, these being placed above the stomach. Connecting with the sophagus after it passes into the chest is a small duct leading to a dilatation within the abdomen known as the crop. From this receptacle food is frequently regurgitated, appearing at the mouth parts in the form of small globules, to be again devoured at the insect's leisure. It is this habit of regurgitation, or vomiting, which renders flies extremely objectionable from a sanitary standpoint, particularly as the stomach contents are obtained in most instances from filth and garbage.

Several segments make up the abdomen or after portion of body, the number varying with the sex and species. The last fo segments in the female form the ovipositor. Owing to its telescop character, this organ may be partially withdrawn within the domen or extended when in the act of depositing the eggs. In t manner eggs are laid in cracks and crevices or deposited beneath surface of filth, thus affording excellent harborage for the lar During the breeding season, which continues throughout the summ months, the abdominal cavity of the female is densely packed w

eggs.

The wings are attached to the thorax and are characterized dark lines or veins extending through the wing membrane, the ma ings varying with the different species. There are three pairs of le all rather thickly covered with hair. Both the legs and wings admirably adapted to the mechanical transference of substances w which they come in contact. It is this interchange of material, rived in many instances from polluted and filthy sources, which c stantly exposes man to the danger of disease.

Reproduction.

Flies are extremely prolific. The stages in the life cycle occu at the most but a few days, and sexual maturity is reached wit three or four days from the date of birth. As the eggs deposi by the female usually number a hundred or more, an enormous crease in the fly population is possible within a short period of ti Like many other insects, flies pass through several developmen stages, the immature forms differing radically from the adult. Th are four stages in the developmental cycle, nam the larva or maggot period, next the pupa, chrys and finally the adult fly. A thorough under these stages is essential for a prer apprecia play in disease transmission.

Nearly all flies breed in org horse manure, but decaying ve human excreta, and putrefying nearly as well adapted to the The barn manure pile may b flies, the unprotected and un nidus for their growth, while food products scattered ab propagation. But three co in filth of this character, food supply. The warm ing garbage heap admi