16 



stopped he went to the place and found the mosquito larvae all through 

 the water as lively as ever, and they began to issue as adults about a 

 week from that time. Again he discovered a place where the water 

 had nearly dried up, and hundreds of mosquito larvae were seen b}^ 

 him on the wet ground. Three days later it rained, and he found the 

 larvre in the water as lively as ever. In the same way Mr. Benjamin 

 S. Paschall, of Newfield, N. J., has conmiunicated to us observations 

 of his own which indicate to liim a possibility that mosquitoes may 

 breed in grass or moist earth. 



Experiments made at this office on a small scale in glass vessels 

 have shown that the larvie of Culex will exist for some little time in 

 wet mud, and some of them will successfully transform after water 

 has been added. In no case, however, were we able to revive larvae 

 in mud from which the water had been drawn off for more than forty- 

 eight hours, and after twcntj^-four hours only a small proportion of 

 the larvae revived. An interesting pool has been under observation 

 during the present month. The pool contained a surface area of about 

 24: s(|uare feet, and was fed entirely by rain water and surface drain- 

 age, reaching a depth when full of about 1 foot. All through the sum- 

 mer this pool is well stocked with mosquito larva\ After a somewhat 

 long drought the water was observed on July 18 to have evaporated 

 almost entirely, a small puddle in the center of the cavity, containing 

 onl}^ 3 or 1 cubic inches of water, remaining. It was dark in color, 

 owing to the drainage from a manure pile near by, and to the casual 

 observer showed no signs of life. The water in this little puddle was 

 very shallow. On dipyjing in a coffee strainer, however, it was found 

 to be literally massed with nearly full-grown mosquito larvae, many 

 hundreds of which had been l^rought together into this restricted 

 place. The drying continued until there was almost no water left. 

 On the night of the 20th came a heavy rain, followed with a still 

 heavier one on the morning of the 22d. On the 23d the pool was 

 found to be entirel}' full of water and to contain its usual stock of 

 mos(piito larvae. 



This may be safely said to indicate the usual habit of mosquito 

 larvae in evaporating pools. As the water gradually recedes toward 

 the deepest portion of the excavation, the larvae recede with it, con- 

 centrating themselves at the deepest point, i. e., at th(> point where 

 the moisture remains longest. Knowing as we do, then, that even 

 in the absence of any free water the larva^ will remain alive in moist 

 mud for from twenty-four to forty-eight hours, it is evident that 

 such a pool as the one described gradually dr3'ing would give the 

 appearance of having been practically dried up for some days before^ 

 the last cubic inch of free water has entirel}^ disappeared. The con- 

 centration of many larvte at this point in the manner which has been 

 described could not fail to give rise to the belief that mosquito larvae 



