OF WASHINGTON, VOLUME XV, 1913. 41 



the leaves of various water-bearing plants, or in water in hollow 

 trees and bamboo stumps, must have been eliminated with the 

 clearing away of the forest. Others, particularly those breeding 

 in smaller pools, undoubtedly have found increased opportunities 

 for breeding within the zone of operations and multiplied proper- 

 tionately at least at times and in places. These opportunities 

 for breeding must have fluctuated greatly with the progress of 

 the work, involving as it does the constant creation of new breed- 

 ing-places and their elimination or control. If it were possible 

 to make a comparative study of the mosquitoes now existing on 

 the Canal Zone with those found by Messrs. Busck and Jennings 

 a few years ago, considerable changes could probably be shown 

 to have occurred. 



Imperfect as our information is, I have data which show that 

 such changes have actually occurred. It would seem that with 

 the creation of Gatun Lake a new element has been introduced 

 into the mosquito fauna, or at least brought into prominence. 

 Among the most important, considered as an annoyance, of tropi- 

 cal American mosquitoes, are the members of the genus Mansonia. 

 M. titillans particularly is very widely distributed, occurring from 

 Argentina to southern Florida, and is an aggressive biter. It 

 is locally sometimes very abundant and troublesome. In working 

 over the mosquito material from the Canal Zone collected by 

 Messrs. Busck and Jennings from 1907 on, the absence of this 

 characteristic species was most striking. Mr. Busck reported it 

 from only one locality, Lion Hill, and Mr. Jennings did not send 

 it in at all. Of a related species, Mansonia fasciolata, Mr. Busck 

 obtained only a single specimen in the Zone, also at Lion Hill. 



Another characteristic tropical mosquito of very wide distribu- 

 tion appeared to be absent from the Zone altogether. This is 

 Aedeomyia squamipennis which ranges from Cuba to Argentina. 

 Like Mansonia titillans, it is local and this local restriction only 

 became comprehensible when the larvae of the two species were 

 found by Mr. H. W. B. Moore of Georgetown, British Guiana. 

 The larvse of both Mansonia titillans and Aedeomyia squamipennis 

 occur associated with the aquatic plant Pistia belonging to the 

 Aracea3. This plant floats in shallow water, its leaves spreading 

 out at the surface, and to its roots the Mansonia larvse are attached, 

 extracting their supply of air from them. Just how intimate the 

 association is in the case of Aedeomyia we do not yet know. 



In lots of mosquitoes, taken recently and sent for determination 

 by Mr. James Zetek, the entomologist of the Canal Zone, both 

 Mansonia titillans and Aedeomyia squamipennis appear in con- 

 siderable proportion. The former is second only to Anopheles 

 albimanus in a catch from traps employed to capture mosquitoes 

 attempting to enter habitations. The Aedeomyia squamipennis 



