2 American Midland Naturalist Monograph No. 3 



The authors are indebted to Drs. E. A. Chapin and Alan Stone of the U. S. 

 Ncitional Museum for helpful suggestions, for assistance in locating critical specimens 

 and for reviewing the manuscript. We wish to express our gratitude to Brigadier 

 General James Stevens Simmons, M. C, Chief, Division of Preventive Medicine, 

 Office of The Surgeon General, U. S. Army; Colonel W. A. Hardenbergh, SnC, 

 Chief, Sanitary Engineering Section of that office; and Colonel Loren D. Moore, 

 M. C, Commanding Officer, 4th Sv.C. Med. Lab., for encouragement and aid. It is 

 also desired to express appreciation to Mrs. Elizabeth Kaston for the illustrations and to 

 the following members of the Entomology Department of the 4th Sv. C. Med. Lab. for 

 valuable assistance: Capt. James P. Toffaleti, SnC, Capt. Harry H. Hoogstraal, SnC, 

 Capt. John A. Carollo, SnC, 2nd Lt. John F. Wanamaker, SnC, Sgts. Daniel Sudia 

 and T. E. Duffey, Leonora Peeples, Jeanne Spence, Frances E. Smith, Winona 

 Gilstrap, Rosemary Baker, and Evelynne Cox. 



Bionomics and Relation to Disease 



Life History 



Mosquitoes undergo a complete metamorphosis, thus passing through 

 four distinct stages during their Ufe cycle; namely, egg, larva, pupa, and 

 adult or imago. 



Egg. — The choice of the larval habitat is made by the female at the time 

 of oviposition. The egg-laying habits of mosquitoes as well as the type of 

 eggs deposited are quite variable but are reasonably similar within a genus. 

 The eggs are deposited singly or in boat-shaped rafts. The females of the 

 genera Culex, Mansonia, Culiseta, and Uranotaenia generally place their 

 rafts of eggs upon the surface of quiet waters, however, the egg raft of Culex 

 apicalis is deposited above the water level on the banks of pools where they 

 remain unhatched until a rainfall causes them to be launched upon the sur- 

 face or the adjacent water. Anopheles females usually lay their eggs on the 

 surface of still waters and as a result of surface tension they are frequently 

 drawn together to form star-shaped clusters. Psorophora and many Aedes 

 deposit their eggs singly in protected places in moist or dry depressions in 

 the ground, where they remain dormant for a considerable period of time 

 before rains, fluctuating tides, floods or melting snows submerge them and 

 permit hatching. In the absence of water many of these eggs are capable of 

 remaining viable for months or even several years. 



Larva. — After the mosquito egg has been in contact with water for a 

 sufficient length of time, the larva cuts its way out by means of the egg 

 breaker on the head and escapes into the water. During growth the larva sheds 

 its skin four times, the stages between moults being called ins tars. 



The food of mosquito larvae consists chiefly of minute plant and animal 

 life and fragments of organic and inorganic debris which are swept into the 

 mouth by the sweeping action of the mouth brushes. Anopheles larvae feed 

 on the surface, while most Culicine larvae feed below the surface of the 

 water. Anopheles larvae rotate the head 180" and with the mouth brushes 

 upward, sweep the surface film for food. Megarhinus larvae and several 

 species of Psorophora are predacious and feed primarily upon other species 

 of mosquito larvae. 



