DESTRUCTION OF PLY LARV^ IN HORSE MANURE^ 1915. 3 



days following the treatment, a pyramidal cage having a flytrap at the 

 top was placed over the pile immediately after the last treatment, 

 and all emerging flies collected in the trap were chloroformed and 

 coimted. The figures given in the tables are for the house fly only. 

 Stomoxys calcitrans, certain species of Phorbia, and various Sarcopha- 

 gidse were often present, but in comparatively small numbers. In ad- 

 dition to the cage and open-pile experiments a few tests were made, 

 placing manure in large wooden boxes which were lined with heavy 

 paper to prevent the migration of larvae through the cracks or corners. 

 Netting and flytraps were attached to the tops of the boxes. , Methods 

 of chemical and bacteriological examination of the manure were prac- 

 tically the same as those employed in previous investigations, and 

 described in detail in Department Bulletin 118 (1), pages 3 to 8, 

 with the exception that nitrates were determined colorimetrically by 

 means of diphenylamin. The examinations were made only in the 

 case of a few substances where favorable larvicidal action was shown. 

 The nitrogen results^ obtained by the distillation method with 

 magnesium oxid (A. O. A. C. method) (7), are included in the tables 

 under the head of amid nitrogen, the ammonia nitrogen as determined 

 by the Folin and Macallum aeration method (4) being deducted from 

 the nitrogen results by the distillation method. 



GENERAL ACCOUNT OF SUBSTANCES USED. 



Most of the substances tested during the past season fall naturally 

 into two groups: (1) Infusions of poisonous plant materials, and (2) 

 fertilizing mixtures. 



PLANT INFUSIONS. 



Plant infusions were prepared by mixing a weighed amount of 

 powdered or finely divided material with a measured quantity of 

 water, stirring well, and allowing the mixture to stand overnight. 

 The resulting infusion was used within 24 hours, applying it to the 

 manure with a sprinkling can from which the nozzle was removed 

 if there was any tendency to clog. In tliis way, the solid as well as 

 the liquid portions of the plant material were directly applied to the 

 manure. The results of cage experiments with plant materials are 

 shown in Table 1, and the results of the open-pile experiments in 

 Table 2. 



1 All nitrogen determinations were made by the Nitrogen Laboratory of the Bureau of Chemistry. 



