BULLETIN OF THE 



No. 167 



Contribution from the Bureau of Entomology, L. O. Howard, Chief. 

 February 10, 1915. 



(PROFESSIONAL PAPER.) 



PARA-DICHLOROBENZENE AS AN INSECT 

 FUMIGANT. 



By A. B. Duckett, 

 Scientific Assistant, Truck Crop and Stored Product Insect Investigations. 



INTRODUCTION. 



The purpose of the following pages is to determine the insecticidal 

 value of para-dichlorobenzene as a fumigant, as well as to ascertain 

 the injury, if any, to cloth fabrics and the effects of the vapors on 

 plant life as well as upon the germination of seeds. 



Para-dichlorobenzene is a definite chemical compound, known for 

 many years, but only recently used as an insecticide. It is a color- 

 less, crystalline substance which volatilizes very readily as a colorless 

 vapor with a peculiar ether-like odor. The vapor is harmless to 

 human beings and domestic animals under ordinary conditions, but 

 in many instances it is a specific poison for insects. It has an addi- 

 tional advantage over the many other fumigants in that the odor 

 does not cling to fabrics, etc., the characteristic ether-like smell 

 rapidly disappearing upon exposure of the fumigated substances 

 to the open air. Probably the greatest advantages that para- 

 dichlorobenzene possesses over other fumigants are its absolute 

 noninflammabihty and its comparatively low cost of purchase and 

 application in proportion to the result obtained. 



EFFECTS OF INHALATION OF THE VAPOR. 



As stated, para-dichlorobenzene possesses only a weak ether-like 

 smell, which, owing to the volatile nature of the substance, will pass 

 off in a few hours if exposed to the air. Dr. Curschman, at the 

 Greppin Works in Germany, concludes from a series of experiments 

 that para-dichlorobenzene, when used as an exterminator for moths, 

 etc., is virtually harmless to human beings, perhaps even superior 

 to naphthalene in this respect. He goes further by stating that 

 poisoning by para-dichlorobenzene to human beings through contact 

 with the skin is impossible and that inhalation of the vapors of this 

 product is perfectly harmless. According to him, para-dichloro- 



71117°— Bull. 167— 15 



