10 BULLETIN 118. U. S. DEPARTMENT OF AGRICULTURE. 



oallons of carbolic acid are heated to 212° F. and to this 150 pounds 

 of finely broken resin and 30 pounds of caustic soda are added and 

 the mixture kept at 212° F. till a dark emulsion without sediment is 

 formed. The resultant emulsion is a good larvicide, 1 part to 10,000 

 parts of water killing mosquito larvae in less than half an hour. 

 However, we did not find it effective against house-fly larva?. The 

 results of three cage experiments are given in Table I, Series A, Nos. 

 1, 2, and 3. Compared with the corresponding controls (Nos. 7, 8, 

 and 9) it seems as if few, if any, fly larva? were destroyed, but the 

 fact that a considerable number of larva? were found in the drip 

 water from the control and only a few from the three treated cages 

 should be considered. 



The chemical analyses, given in Table I, show variation in the 

 total nitrogen of the treated and control manures. This is true of 

 many of the samples analyzed and shows the normal variations. 

 The water extract of the treated manure showed more nitrogen and 

 ammonia present than did the water extract of the control manure. 

 The reactions of the water extracts varied considerably. No nitrites 

 or nitrates were present either in the larvicide treated or in the 

 control manure. 



Unfavorable action on the bacteria is shown where the numbers 

 are progressively decreased as the volume of the larvicide was in- 

 creased. The highest count for the iarvicide-treated samples is 

 considerably lower than the lowest control count. 



Several open-pile experiments were also carried out. One of these 

 was started September 15 and the treatment repeated on four suc- 

 cessive days. From the resulting pile of 32 bushels of manure about 

 10,000 pupa? were taken on September 26. The control pile contained 

 about 7,000 pupa?. This was a typical experiment and is sufficient 

 to show that even with repeated daily applications this reagent is of 

 no value as a maggot destroyer. 



IRON SULPHATE. 



The results of three cage experiments with iron sulphate are given 

 in Table I, Series A, Nos. 4, 5, and 6. The controls for these are 

 Nos. 7, 8, and 9. The total number of flies caught from these cages 

 shows that the manure was rather lightly infested. However, a 

 comparison of the total number of flies that emerged and the number 

 of larva? found in the drip pan from treated and untreated cages 

 indicates that this chemical may have had some larvicidal power. 

 However, in three other cage experiments not shown in the table 

 no larvicidal action was evidenced. 



Iron sulphate was not used on open piles. The chemical and bac- 

 teriological findings in Table I show an injurious action on the 



