306 APPLIED ENTOMOLOGY 



large, rounded mass, joined by a slender abdomen. Differing from 

 most insect pupae, the pupal mosquito is active, moving through the 

 water by a curious tumbling end over end. On the top of the thorax 

 in this stage are two breathing tubes (Fig. 322), and when air is desired 

 the tips- of these are pushed above the surface of the water. The animal 

 swims by making use of a pair of leaf -like appendages at the end of the 

 abdomen. 



After a brief pupal stage, usually lasting only a few days, the animal 

 comes to the surface of the water and a split of the pupal skin along the 

 middle of the back of the thorax appears, through which the adult 

 mosquito escapes, balancing itself on this skin until it is ready for flight. 



FIG. 322. Pupa of Anopheles (left) and of Culex (right) showing position when breath- 

 ing. Difference of form, position in the water and in the breathing tubes are shown. 

 Greatly enlarged. (Modified from U. S. D. A. Div. Ent. Bull. 25, n. s.) 



Of the many kinds of mosquitoes known, a small number are of 

 particular importance aside from their habit of attacking man, being 

 disease-carriers. 



The House Mosquito (Culex pipiens L.). This is a very common 

 species almost everywhere in the Northern United States east of the 

 Mississippi River and north of North Carolina. It is probably a native 

 of the Old World where it is also abundant. Though as far as known it 

 is not a carrier of any human disease yet it is a most irritating pest, and 

 its control is important on that account. 



Winter is passed as the adult (Fig. 323) in protected places and, in 

 spring, egg clusters containing from 100 to about 300 eggs are laid on the 

 surface of water. These eggs hatch in from 1 to 4 or 5 days and the 

 larval stage usually continues for a week or two (Fig. 324) . During this 

 period, the larvae spend much of their time at the surface, the respiratory 

 tube projecting slightly above the water-line and the body hanging 

 downward. Pupation for a few days follows, after which the adult 

 appears. There are a number of generations each season. The adult 



