Numbers, 76; interest and importance, 76; eggs, 77; always in water, 77; time of hatching, 77; _Larvæ_, 78; live only in water, 78; head and mouth-parts of larvæ, 78; what they feed on, 78; breathing apparatus, 79; growth of the larvæ, 80; _Pupæ_, 80; active but takes no food, 80; breathing tubes, 80; how the adult issues, 81; _The Adult_, 81; male and female, 81; how mosquitoes "sing" and how the song is heard, 82; the palpi, 82; _The Mouth-parts_, 83; needles for piercing, 83; _How the mosquito bites_, 84; secretion from the salivary gland, 84; why males cannot bite, 84; blood not necessary for either sex, 84; _The Thorax_, 85; the legs, 85; the wings, 85; the balancers, 85; the breathing pores, 86; _The abdomen_, 86; _The digestive system_, 86; _The salivary glands_, 87; their importance, 87; effects of a mosquito bite, 87; probable function of the saliva, 88; _How mosquitoes breathe_, 89; _Blood_, 90; in body cavity, 90; heart, 90; _Classification_, 91; _Anopheles_, 91; distinguishing characters, 92; eggs, 92; where the larvæ are found, 93; _Yellow fever mosquito_, 94; its importance, 94; the adult, 95; habits, 95; habits of the larvæ, 95; _Other species_, 96; some in fresh water, others in brackish water, 96; Natural enemies of mosquitoes, 97; how natural enemies of mosquitoes control their numbers, 98; mosquitoes in Hawaii, 98; _Enemies of the adults_, 99; _Enemies of the larvæ and pupæ_, 100; _Fighting mosquitoes_, 101; fighting the adult, 102; _Fighting the larvæ_, 103; domestic or local species, 104; draining and treating with oil, 104; combatting salt-marsh species by draining, 105; by minnows or oil, 105. CHAPTER VII MOSQUITOES AND MALARIA 106 Early reference to malaria, 106; its general distribution, 106; theories in regard to its cause, 107; insects early suspected, 107; _The parasite that causes malaria_, 108; studies of the parasite, 108; _Life-history in human host_, 109; its effect on the host, 110; the search for the sexual generation, 111; _The parasite in the mosquito_, 112; review of whole life-history, 115; malaria transmitted only by mosquitoes, 115; _Summary_, 117; experimental proof, 118. CHAPTER VIII MOSQUITOES AND YELLOW FEVER 120 A disease of tropical or semi-tropical countries, 120; outbreaks in the United States, 120; parasite that causes the disease not known, 121; formerly regarded as a contagious disease, 122; _The yellow fever commission_, 123; Dr. Finlay's claim, 124; experiments made by the commission, 125; summary of results, 129; what it means, 130; _results in Havana_, 131; _the fight in New Orleans_, 132; _In the Panama canal zone_, 135; _in Rio de Janeiro_, 136; claims of the French commission, 138; _habits of stegomyia_, 139; breeding habits, 139; possible results of war against the mosquitoes, 139; Danger of this disease in the Pacific Islands, 140. CHAPTER IX FLEAS AND PLAGUE 142