198 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL.84 



course of their cotton insect work. For example, R. H. Van Zwalu- 

 wenburg worked in Mexico for some time in the employ of an 

 American company in the State of Sinaloa, and in 1926 published a 

 report on the insect enemies of sugar cane in western Mexico. A. W. 

 Morrill was also for several years in the employ of a great American 

 company in Mexico largely engaged in the growing of vegetables. 

 He has published several articles upon his work, an especially notable 

 one being an account of the use of the airplane in dusting large plan- 

 tations of tomatoes. In a special publication of the California De- 

 partment of Agriculture in 1927, Doctor Morrill gives the result of 

 five years' experience in conducting a general survey of the pests of 

 crops on the west coast of Mexico. 



An important publication which we have not yet mentioned was 

 published by the office of Defensa Agricola in 1929. It is entitled 

 (translated) "Arsenic and Its Derivatives as Insecticides." It was 

 written by two chemical engineers, Pablo Hope y Hope and Manuel 

 de la Lama, both connected with the service. 



