DESTRUCTION OF THE HOUSE FLY. 123 



Finally, the question of mosquito extermination or 

 abatement, I believe, can only be satisfactorily settled by 

 a conducted movement over wide tracts of land. The ar- 

 rest of the plague in one portion of the country, when the 

 next section makes no eflPort to suppress its own annual 

 contingent, can only lead to discouragement and ridicule. 

 The approval of local authorities and the appropriation of 

 a fund for the purpose will greatly aid the cause of mos- 

 quito extermination, and especially the location of the 

 worst infected regions, whose baneful progenies are carried 

 far and wide over their afflicted vicinities.* 



THE DESTRUCTION OF THE HOUSE FLY. 



I DO not think it is possible to introduce the dragon fly 

 into the streets and houses in cities for the purpose of using 

 it as an instrument of attack against the house fly (Mus- 

 ca domestica L.). The latter, from habits, has become 

 completely domesticated, while the former retains all its 

 wild nature unsubdued and unchanged, has undergone no 

 experience which would tend to divorce it from its out- 

 door life, and probably it cannot be modified in this re- 

 spect, even after long habituation to new conditions. Its 

 natural voracity might disappear under such circumstances, 

 or its tastes be altered. Its aerial and sunny existence 

 could hardly submit to such a violent change without 

 some corresponding modification of its nature. 



* Prof. E. P. Whitfield informs me that some years ago while 

 he was staying at Atlantic City, N. J., he noticed that people of 

 that town were using an astringent in the water to kill the mos- 

 quito larvae which were at the time very numerous, and upon 

 inquiries made by him was informed that the chemical used for 

 the purpose was copperas (ferrous sulphate). 



