POSSIBILITIES AND COSTS. 57 



V. 

 THE POSSIBILITIES AND COSTS. 



The insecticide substances and other means for arthro- 

 pod extermination now known to economic science are 

 legion. An acquaintance with their properties, and a 

 knowledge of the experiments which have been made 

 with them, require years of study and research. It is not 

 our design to treat of tlie mctliods of the work already 

 done, or the nature of most of these remedies. A fair 

 understanding of the former may be obtained by consult- 

 ing Comstock,^^ and the latter by referring to Riley.'-*"^"'^ 



There are some insecticides which can best be discussed 

 at this time. They are substances as will by their union 

 with water destroy larval life. Chief among these is the 

 well known pyrethrum or Persian insect powder. That it 

 is one of our most important insecticides may be judged 

 from the prominence given it in all our Government re- 

 ports. But it is far too expensive to be of practical value 

 in the cases now under our consideration. To mix it in 

 ponds or pools, or heaps of compost, in sufficient quantities 

 to overcome dipterous larvse, is quite beyond our calcula- 

 tions. To attempt to use it against the adult fly or mos- 

 quito is equally visionary. Various insecticides which 

 come next in importance, as best adapted to the conditions 

 in which larval Culex and ]\Iusca are to be found, are 

 naphtha, sulphurous exhalations, ammoniated water, and 

 naphthalin. None of them, however, are sufficiently cheap 

 or easy of application to answer our purposes. The reader 

 may consult Cornelius,'^ Kiley,^-^ Gratacap,^ and Miot.^^ 

 As partaking of the nature of the above, and being cheap 



