Apr. 12, 1924 



Development of American Foulbrood 



145 



Table IV. — Average chemical composition of worker larvce at (liferent ages, compiled 



from Straus (43) 



o Calculated by interpolation and averaging. 



CHOICE OF REAGENT 



It was necessary to devise a special technic for the determination of the unassimi- 

 lated reducing sugar in the larva by the application of procedures used in other 

 analyses where small amounts of reducing sugars must be determined, such as in 

 urine analysis. After studying the various methods of sugar analysis, a volumetric 

 titration method seemed the most promising. 



For the purpose of determining quantitatively the unassimilated sugar in the 

 bee larva at different ages, the modified copper sulphate solution of Benedict (5) 

 was chosen, mainly because, as in urine analysis, it has proved more satisfactory 

 than any other titration method for determining small amounts of reducing 

 sugars quantitatively, and because this solution keeps indefinitely .without 

 deteriorating. The potassium sulphocyanate in the solution produces, upon 

 reductioil of the sugar, a white precipitate of cuprous sulphocyanate, which per- 

 mits the end point of the reaction to be more accurately determined than with 

 Fehling's solution. A trace of ferrocyanid is added to prevent precipitation of red 

 cuprous oxid which, may be caused by certain impurities, which would interfere 

 with the determination of the end point. The test solution is standardized to a 

 known solution of dextrose so that 5 cc. equals 0.0102 grams of dextrose. 



CHOICE OF LAKVAE 



Since there is little likelihood of there being any appreciable amount of sugar 

 elsewhere than in the intestine, analyses were made of entire larvse, because of 

 the great difficulty attending the dissection of the intestines. Larvse for analysis 

 were chosen from combs having large areas of brood of uniform size and age. In 

 most cases 35 larvae as nearly of the same size as possible were carefully removed 

 from the cells by means of a pair of fine forceps, care being taken to remove as little 

 uningested food as possible. Any visible amount of adhering food was removed 

 with filter paper and the 25 larvse were weighed. Several series were weighed for 

 each age above the two-day age period through to about the fourth day after 



capping. 



DETERMINATION OF AGE OF LARVAE 



When choosing larva for the analysis, the approximate age was determined by 

 comparison with drawings to scale by Nelson and Sturtevant (35) of larvse of 

 known age at various age periods, 24 hours apart. Nelson and Sturtevant, as 

 5095— 24t 3 



