PREDACEOUS MOSQUITO LARV^ 167 



from them. It may be mentioned, however, that one of us (Knab) has seen 

 agrionid larv'ae come to the surface of the water and seize Culex larvae. 



We are of the opinion that dragon flies do destroy a great many mosquitoes. 

 While they show no preference for mosquitoes there seems to be, on the part of 

 adult dragon flies, a marked preference for Diptera ; with their great rapidity 

 and activity, where mosquitoes are abundant, a considerable number must be 

 destroyed by them. This must be particularly true of the large crepuscular 

 species, such as JEschna, their time of activity coinciding with that of most 

 mosquitoes. Mr. Nathan Banks tells us that, at College Station, Texas, he has 

 observed a large dragon fly capturing flying insects in rapid succession, pre- 

 sumably mosquitoes, as a great many of these were flying about at the time. Mr. 

 McAfee, at Church's Island, North Carolina, has seen a dragon fly (Enjthemis 

 simplicicoUis) pick Anopheles quadrimacuJatus off the weather-boarding of a 

 house. 



Certain ephemerid larvas are active destroyers of mosquito larvae. Foley and 

 Yvemault found that in Algeria ephemerid larvae are more efficient destroyers 

 of mosquito larvae than Dytiscidae. 



Some very efiicacious natural enemies of mosquitoes are to be found in the 

 family Culicidae itself. The larvae of Psorophora, Megarhinus, Lutzia and 

 Lesticocampa are voraciously carnivorous and even cannibalistic, while the 

 larger larvse of Anopheles will attack one another and the larvae of other mos- 

 quitoes. In a lot of larvae of Anopheles quadrimaculatus and A. punctipennis, 

 kept in the laboratory in a large battery jar for study by one of us, the larvae 

 were noticed to disappear, and one morning nine heads were found of which the 

 bodies were gone. Nothing but mosquito larvae were in the jar. One larva was 

 noticed which looked as if it had two heads, but upon examination it was found 

 that the body of one had been almost devoured and the survivor was eating the 

 head which was all that was left of the victim. Several larvae were found which 

 had been half eaten. The Anopheles larvae were several times seen eating the 

 young Culex larvge. The cannibalistic tendencies of Anopheles larvae have been 

 noted repeatedly by a number of writers. The larvse of certain species, having 

 a restricted habitat in the water in holes of trees and between the leaves of brome- 

 liads, are probably entirely predaceous. 



Dr. Oswaldo Cruz, of Brazil, while on a visit to Washington, stated that in 

 Rio de Janeiro Lutzia bigotii is used practically to destroy the larvae of Aedes 

 calopus. The Lutzia larvae are introduced into receptacles in which the calopus 

 breeds and soon destroy the larvas of this dangerous insect. 



The habits of Psorophora in the larval stage are such as to make them very 



desirable inhabitants of stagnant pools. They have been frequently described, 



but the series of observations made at the request of one of us by Dr. W. E. 



Hinds, in the summer of 1901, and hitherto unpublished, will be of interest 



here. The following extract from Doctor Hinds' notes, treats of the feeding 



methods of the larvae : 



" August 16. A. M. Received a lot of Psorophora ciliata larvae from W. P. 

 Seal, Delair, N. J. They came in a large quart bottle and with them were quite 



