Numbers, 40; importance, 41; losses caused by insects, 41; loss of life, 42; _The flies_, 43; horse-flies, 43; stable-flies, 44; surra, 45; nagana, 45; black-flies, 46; punkies, 46; screw-worm flies, 47; blow-flies, 48; flesh-flies, 48; fly larvæ in intestinal canal, 49; bot-flies, 50; _Fleas_, 52; jigger-flea, 53; _Bedbugs_, 54; _Lice_, 54; _How insects may carry disease_, 55; in a mechanical way, 55; as one of the necessary hosts of the parasite, 56. CHAPTER V HOUSE-FLIES OR TYPHOID-FLIES 57 The old attitude toward the house-fly, 57; its present standing, 58; reasons for the change, 58; _Structure_, 59; head and mouth-parts, 60; thorax and wings, 61; feet, 62; _How they carry bacteria_, 62; _Life-history_, 63; eggs, 63; ordinarily laid in manure, 63; other places, 63; habits of the larvæ, 64; habits of the adults, 64; places they visit, 65; _Flies and typhoid_, 65; patients carrying the germs before and after they have had the disease, 65; how the flies get these on their body and distribute them, 66; results of some observations and experiments, 66; _Flies and other diseases_, 68; flies and cholera, 68; flies and tuberculosis, 69; possibility of their carrying other diseases, 70; _Fighting flies_, 71; screens not sufficient, 71; the larger problem, 71; the manure pile, 72; outdoor privies, 72; garbage can, 72; coöperation necessary, 72; city ordinances, 73; an expert's opinion of the house-fly, 73; _Other flies_, 75; habits of several much the same but do not enter house as much, 75; the small house-fly, 75; stable-flies, 75; these may spread disease, 75. CHAPTER VI MOSQUITOES 76