THE COMMON MOSQUITO 87 



men will get hold of a bubble of gas forming at the bottom, and 

 will allow itself to be floated to the surface. It is immensely inter- 

 esting to watch these little creatures ; but as week after week 

 went by without change it became just a little tedious. To has- 

 ten matters a little, on March 1st I placed the two jars first re- 

 ceived on a water bath, which was kept at a temperature as nearly 

 constant as the varying gas pressure allowed. Ordinarily the 

 thermometer ranged between 100° and 110°, but it has gotten as 

 high as 120° and as low as 90°. These were exceptions, however, 

 and not exceeding the ordinary out-door range in June. The 

 temperature of the water in the jars ranged between 80*' and 90' 

 almost uniformly. 



A difference in the rate of growth was observable after a few 

 days, and several specimens seemed approaching the adult con- 

 dition ; finally, on March 18th, I noticed the first pupa, seven- 

 teen days after placing the jar on the water bath. From this 

 the adult emerged March 21st and proved to be a female Culex 

 pungens. Three other pupae were formed within a week after the 

 first, and a second adult, also a female, Avas obtained March 24th. 



As to the habits of the larvae in the two jars artificially forced 

 there was little to note as different from those in the normal 

 laboratory temperature, which varied from 40° to 78°, averaging 

 a little under 70° for the twenty-four hours. They fed in much 

 the same manner, kept away from the light as much as possible, 

 passed most of their time at the bottom, but were more lively 

 and more frequently at the surface. The jars were kept covered 

 except for a few minutes each day and in none of them did the 

 water foul, despite the vegetable and animal matter present in 

 each. 



On March 24th I made an experiment that resulted fatally. It 

 occurred to me that possibly the slow growth was due to lack of 

 food, and Mr. Brakeley had written me that the wrigglers at- 

 tacked and devoured a small gnat which was breeding in his jars, 



