424 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 31 



of Ghara introductions the breeding habits of our northern species 

 of mosquitoes must be borne in mind. All our Aedes species pass 

 the winter in the egg stage, the eggs being deposited throughout the 

 summer on the bottoms or margins of dried-out or greatly lowered 

 pools. These eggs, with the possible exception of Aedes vexans^ 

 do not hatch till the following spring. All our species of Culex^ 

 Anopheles^ and most of our Tlieobaldia pass the winter as adults 

 and oviposit on water during the following spring or summer. It 

 will thus be seen that we have practically only one brood of the 

 Aedes species each season, whereas there may be several broods of 

 Culex, Anopheles, or Theohaldia species. There are exceptions to 

 this general summary, but the main thesis holds true for the species 

 under experimentation with Ghara. In any attempt to introduce 

 Ghara into pools which dry up during the summer the question of 

 the renewal of growth the following season was problematical. 

 However, for a number of j^ears Ghara fragilis was found growing 

 in temporary puddles which dried out each season, so it was thought 

 that introductions into similar pools might prove successful. Fur- 

 thermore, the kind of water which would support Ghara was not 

 known, and no information was available on the culture, growth, 

 etc., of Ghara species. 



It may be worth while to present the details of two introductions. 



Buttermilk Falls pool. — This pool (pi. 6, fig. C.) is rather 

 small and is spring fed. It is about 8 feet in diameter and 2i/^ 

 to 3 feet deep. Aedes canadensis breeds here in great abundance 

 during the early spring and is followed by Aedes., vexans, Gulex 

 apicalis, Gulex territans, and Anopheles punctipennis. The main 

 object of the experiment was to obtain a good growth of the Ghara 

 which might prevent the breeding of the summer species and also 

 prevent the oviposition of Aedes canadensis and Aedes vexans. The 

 results of this experiment are shown in Table 4. 



Table 4. — Buttermilk Falls pool 



Date 



1923 



Apr. 7... 

 Apr. 9... 

 Apr. 18.. 

 May 2.. 

 May 13- 

 May 17. 

 May 31. 



June 7.. 



June 13 



June 16 to 28. 

 July 3 



July 5 to Sept. 6. 



Condition of Chara 



Introduced 4 pails of Chara... 



Not growing 



do 



Growth begins 



Good growth 



do 



Slow growth. 



Vigorous growth 



do 



Good growth, but decay area 



in center. 

 Vigorous growth, but a central 



area of marked decay. 



Eesults 



Numerous larvp.c of Aedes canadensis. 

 Larvae very inactive, due to cold. 

 Larvae abundant, growth slow. 



Do. 

 Larvae abundant; a few pupae. 

 Pupae nuinorous. 

 Anopheles punctipennis, Cule.t apicalis, a few small 



larvae. 

 Anopheles punctipennis, 2 largo larvae. Culex apicalis, 



a few small ones. 

 No brooding; larvae and pupae in near-by pools. 

 No lireeding; near-by pools dry. 

 Culex aijicalis, few small larvae; .Anopheles, a few 



larvae. 

 Culex apicalis and Anopheles punctipennis bred in fair 



numbers throughout this period. 



