28 INSECTS OF ECONOMIC IMPORTANCE 



Water 2 fluid ozs. 



Sulphuric acid lYi. fluid ozs. 



Sodium cyanide i oz. 



For house fumigation ^^ all holes in rooms should 

 be stopped and all cracks covered with strips of 

 newspaper soaked in water. 



In fumigating trees tents are used.^^ In fumi- 

 gating nursery stock for scale insects a special room 

 is needed.^^ 



Formaldehyde gas — This is primarily a germi- 

 cide. It has been shown to be practically useless 

 as an insecticide. , 



Tobacco papers — Paper soaked in tobacco ex- 

 tract is sold for fumigation purposes in green- 

 houses. These papers will burn when lighted and 

 are much more convenient to use in houses than 

 tobacco stems. 



HEAT^i 



AMthin the last few years heat has been used 

 to some extent in mills in the western part of the 

 United States, at least, to kill mill insects. Ac- 

 cording to Dean and Goodwin heat is a very effi- 

 cient and satisfactory agent for destroying grain 

 insects. The temperature necessary to kill stored 

 grain insects ranges from 118° to 125° F. Felt 

 has shown that cockroaches succumb to a tempera- 

 ture of 120° F. It is necessary to maintain the 

 heat for several hours to allow it to penetrate all 



58 Howard and Popenoe — U. S. Bu. Ent., Circ. 163. 

 Herrick — Can. Ent., Vol. 39, p. 341. 



59 Morrill— U. S. Bu. Ent, Bull. 76. 

 Woglum— U. S. Bu. Ent., Bull. 79. 

 Woglum— U. S. Bu. Ent., Bull. 90, Parts I and II. 



^° Britton — Conn. Expt. Stat., Bull, of Immediate Information 

 No. 3. 



61 Goodwin — Ohio Expt. Stat., Bull. 234. 



Dean— Kan. Expt. Stat., Bull. 189. 



Felt— 27th Rept. State Ent., N. Y. 



