312 AGRICULTURAL EXPERIMENT STATION. 



larva varies somewhat in the length of the anal siphon and of 

 the anal gills, but not enough tO' be confusing. 



Habits of the Bcirly Stages. 



This larva or wriggler may be found almost anywhere in 

 stagnant water. There is no place so small and no water so foul 

 as tOi bar this species. Anything from a tin can half full of rain 

 water to- a sewer basin, cesspool or manure pit will answer. Any 

 pool of rain water that lasts eight or ten days, a bucket, a tub 

 or other receptacle left outdoors, a rain barrel or even a watering 

 trough that is rarely emptied will serve. In cities and towns the 

 sewer basins form an important source of supply. Where there 

 are no^ sewers, cesspools answer as well, and where rain barrels 

 or cisterns are in use these are favorite breeding places. Ne- 

 glected gutters in the outskirts of a city or town, sunken lots in 

 which water accumulates, ditches along the roads when allowed 

 to become overgrown and to' become choked — all these are pro- 

 lific sources of supply. And they will breed indoors as well as 

 out if they are given a chance. I have found a brood in a battery 

 jar left half filled with water in the laboratory, and have seen 

 wrigglers^ in the concave floor below a shower bath which had 

 become filled because of a plug in the waste pipe. In one of the 

 leading seashore resorts many of the large hotels have a space 

 from two tO' six feet below the basement floor in which pools 

 form from surface drainage and in- these pools larvae develop 

 in countless numbers. They find their way through the elevator 

 shafts into the house and throughout the rooms to the great dis- 

 comfort of the guests. I found by experience that I could leave 

 my windows open safely at night, if only I closed the fanlight into 

 the hall. It is this ability tO' develop almost anywhere that makes 

 Culex pipiens oiu* most common and widely distributed species. 



After hatching from the tgg as already described, the larva 

 requires from six to eight days to attain full growth. The former 

 is the minimum period in mid-summer when food is plentiful ; 

 the latter is the more usual period. When the weather is cold 

 and the water clean it recjuires a longer period and the resulting 

 adult tends tO' become dwarfed. The same effect is produced 

 when a pool dries up so fast as tO' crowd the insects and force 

 them into the pupal stage. 



In the pupal stage the insects remain for two- or three days, 

 sometimes longer if the weather be cold. Rarely the entire de- 

 velopment from tgg to adult is crowded into one week. 



