wide, and 4 feet deep will hold the manure produced by two horses during about five months. About 2 cubic feet of box space should be allowed for each horse per day. The bin should be made of concrete or heavy plank. When the latter is used the cracks should be battened to prevent the escape of flies. The bin may have a floor or it may be set in the ground several inches and the dirt closely banked around the outside. For the admission of the manure a goodsized door should be provided in either end of a large bin. A portion of the top should be made easily removable for convenience in emptying the box, or one entire end of the box

may be hinged. On ac

count of the danger of the door being left open through carelessness, it is advisable to arrange a lift door which can be opened by placing the foot on a treadle as the manure is shoveled in. The door should be heavy enough to close automatically when the treadle is released.

In buildings where flies are not very abundant, sticky fly paper is fairly efficient in reducing their number. A solution containing three teaspoonfuls of sodium salicylate in one pint of water may be placed in saucers around the room, and it will be found that many flies will be killed by drinking thereof. It is necessary, how

M

D

I

-B

FIG. 38.-Conical hoop flytrap; side view. A, Hoops forming frame at bottom. B, Hoops forming frame at top. C, Top of trap made of barrel head. D, Strips around door. E, Door frame. F, Screen on door. G, Buttons holding door. H, Screen on outside of trap. I, Strips on side of trap between hoops. J, Tips of these strips projecting to form legs. K, Cone. L, United edges of screen forming cone. M, Aperture at apex of cone. Bishopp.

Care should be taken drink the water, as

ever, to remove other liquids from the room. to see that children and animals do not sickness may result therefrom. This solution may be placed in a tumbler and the latter inverted over a piece of blotting paper in a dish. The solution gradually oozes through the blotting paper upon which the tumbler rests and thus becomes accessible to the flies.

Mosquitoes.

Most mosquitoes lay their eggs upon the surface of water. In some species these adhere together in raft-like masses. In summer time the larvæ, or "wiggle tails," hatch in one or two days. Although they live in water, they must, with the exception of one unimportant species, either lie on its surface or come frequently to the surface to breathe. In a few days the larvæ change into pupa, or "tumblers," from which the winged insect emerges through a rent in the pupa case and flies away. The whole process, from the

FIG. 39.-Use of flytrap in connection with manure bin. A, Block of wood set in ground to which lever raising door is hinged. Bishopp.

laying of the egg to the emerging of the adult insect, requires from 9 to 15 days, or, if the water is cold, sometimes as much as 22 days. Some species hibernate in the egg form.

The different parts of an adult mosquito are shown in figure 42. There are a number of species of mosquito, each varying slightly from the other. Only female mosquitoes are blood-sucking insects; male mosquitoes are vegetarians and do not bite man or animals. For some species blood appears to be necessary to the female mosquito for the full development of its eggs.

The breeding places of mosquitoes depend to a great extent upon the species. The yellow-fever mosquito and the domestic mosquito

breed around houses, in any small collection of water that may be present in tin cans, bottles, flowerpots, pools, gutters, sewers, etc. Malarial mosquitoes may be found breeding in such places, but this mosquito usually prefers the margins of ditches and lakes, especially where reeds and water plants are found, as in swamps and low bottom lands. Near the seacoast there are other mosquitoes which breed only in brackish water, but these, although annoying, do not transmit disease to man. Mosquitoes may be blown many miles by the wind, but it is not usual to find those that transmit disease very far from their breeding places. The presence of mos quitoes in a house is good evidence that they are breeding in some place near the house, and very often a search will be rewarded by the finding of wiggle tails in some small collection of water. They are often carried by trains and boats for long distances, and the spread of yellow fever from one country to another is accounted for to a great extent by infected mosquitoes being carried in this way. During the winter some species of mosquitoes hibernate in cellars and dark cor

ners; in others, the larvæ or eggs resist cold, and they even hatch out after being frozen.

The diseases known to be transmitted by mosquitoes are malaria, yellow fever,

dengue, and filariasis. Three conditions are necessary before these diseases can be spread from one person to another. First, a person must be bitten by a certain kind of mosquito-malaria is only transmitted by Anopheles mosquitoes; yellow fever by a striped black and white mosquito called Aedes calopus; a mosquito known as the Culex fatigans, and probably some others, are believed to carry the germs of dengue; while filariasis is spread by several varieties of mosquito. Second, the mosquito must have been infected by previously biting some person who has the germ of the disease in his blood. Third, some time, varying with the different diseases, for some not less than 8 or 10 days, must elapse between the time the mosquito bites the person suffering from the disease and the biting of the well person. The reason for this, in the case of malaria, is explained by Surgeon Carter as follows:

If the mosquito sucks up only sexless parasites with the blood she will not become infected, no matter how many she takes. If, however, the proper kind of mosquito takes up the male and female forms of the parasite they join together in her stomach and pass into her stomach wall, where they grow. After some time the bodies thus formed break and set free many young parasites,