Carpenter et al.: Mosquitoes of Southern U. S. 3 



The duration of the larval stage depends upon inherent characteristics 

 of the species concerned and upon several external factors, such as water, 

 temperature, and the availability of a suitable food supply. Under optimum 

 conditions many species of mosquitoes pass through the larval stage in about 

 a week to ten days, while others may stretch this period into several months. 

 Some of the temporary pool breeders pass through this stage in 4 to 5 days. 

 Mosquito larvae are found in nearly all types of permanent and temporary 

 waters, both fresh and brackish. Specific reference to the typical larval habitats 

 will be found under the discussions of the individual species. 



All mosquito larvae, except those in the genus Mansonia, must come to 

 the surface of the water at periodic intervals to renew their supply of oxygen. 

 The Mansonia larvae as well as pupae attach themselves to the underwater 

 portions of certain aquatic plants and secure their oxygen from the plant 

 tissues. 



Pupa. — With the fourth moult the pupa or '"tumbler" stage appears. 

 Unlike the larvae, the pupae are lighter than water and do not feed. They 

 are very sensitive to disturbances of the water and will go downward very 

 rapidly in a jerking, trembling motion when disturbed. A pair of large breath- 

 ing tubes (trumpets) on the cephalothorax enables the pupa to break the sur- 

 face film and obtain atmospheric oxygen. The pupal stage lasts but a few 

 days (usually 2 or 3) then the pupa extends its abdomen parallel to the 

 surface film in preparation for the emergence of the adult. 



Adult. — When the adult is ready to emerge it swallows some of the air 

 enclosed within the pupal skin and by increased muscular action and internal 

 pressure causes a split to occur on the dorsum of the cephalothorax, per- 

 mitting the adult to emerge. The newly emerged adult uses the cast skin or 

 adjacent vegetation as a float and remains quiescent for a short period of 

 time sufficient to dry and harden its body before flying away. 



The species of Anophelines and Culicines vary considerably in their hab- 

 its, and the habits of the larvae and adults are particularly diversified. Only a 

 brief discussion of the more obvious characteristics is included here. 



The food of a female mosquito includes not only the nectar of flowers 

 and the juices of fruits, but also, in all but a few of our species, animal blood. 

 The maxillae and mandibles of male mosquitoes are insufficiently developed 

 for blood sucking purposes, consequently the male is an obligatory vegetarian. 



The majority of the Anophelines and many of the Culicines feed by 

 preference during the twilight hours of morning and evening, although 

 some will attack in direct sunlight as well. The females continue to feed 

 throughout their life, which in non-hibernating species may, in exceptional 

 cases, be as long as several months. 



It appears that warm-blooded animals and birds are the most common 

 sources of blood, however, even cold-blooded vertebrates are attacked by 

 some species. Some mosquitoes are opportunists and will attack indiscrimi- 

 nately any warm-blooded animal encountered (zoophilism) . On the other 

 hand, certain species, among which are numbered some of the Anopheles, 

 show a marked predilection for the blood of man (androphilism) . Domes- 



