160 Annals Entomological Society of America [Vol. XV, 



and two of A. excriicians were taken in a deep pool on open 

 ground. The pool had a mud bottom covered with leaves. 

 On April 21, Mr. Sibley brought in from Ringwood a great 

 number of mature larvae and pupae. This material consisted 

 of two species, stiniiilans and excriicians (abfitchii). A large 

 number of isolations were made, but they proved difficult to 

 rear under artificial conditions. However, seventeen adults 

 were secured, the last larval and pupal skin being saved. 

 These were all mounted and 5 proved to be excrucians and 12 

 stimulans. Of these we had 4 males of excrucians and 6 males of 

 stimiilans. Not a single fitchii larva was found in this col- 

 lection. Mr. Sibley reported that these larvae and pupae were 

 present in immense numbers. 



On May 10, the writers visited Ringwood and located the 

 pool described by Mr. Sibley. It was the last of three pools 

 situated in the woods in a line back from the roadway at an 

 elevation of about 1300 feet. The first pool was covered over 

 by a dense mat of duckweed and in this no mosquito larvae 

 were found. The second pool which is of considerable size 

 and depth, is evidently a pothole and is isolated from the other 

 two. Practically no aquatic vegetation was present and the 

 bottom and margins had a dense covering of decaying leaves 

 and mud. Immense numbers of pup« and relatively few 

 larvae were present along the edge and about floating tree trunks 

 in the pool. None were found in the open water where it was 

 deeper than three feet. The presence of such vast numbers 

 was all the more surprising, as Mr. Sibley found none in it 

 on April 21st. A greater surprise awaited us when we learned 

 that this vast number of larvae and pupae in pool number two 

 consisted of but a single species — a pure culture of A . fitchii. 



Pool number three, which is similar but smaller than 

 number two, did not contain at this time a single larva. It was 

 in this pool that Mr. Sibley, eighteen days earlier, found such 

 immense numbers of A. stimulans and A. excrucians. 



These observations are of interest in showing an instance of 

 two species, A. stimulans and A. excrucians, inhabiting but a 

 single pool, even though a second pool of similar character 

 is only a short distance away. Then a third very closely allied 

 species, A. fitchii, occupies the second pool, to the exclusion 

 of the one occupied by the first two species. Another point 



