332 PRINCIPLES OF STOCK-BREEDING. 



that the workers, although incapable of impregnation, 

 may sometimes lay eggs that produce drones. Eggs 

 producing females are, however, only laid by the queen, 

 and then only after impregnation. 1 It appears that 

 all unimpregnated eggs produce males, and all im- 

 pregnated eggs produce females i. e., either workers 

 or queens : and the male element of fertilization, in 

 the case of bees, would seem, therefore, to be essential 

 to the production of females only. 



The theory that sex is determined by the activity 

 of the nutritive processes has been recently advocated 

 by naturalists. 



Mrs. Mary Treat, in the American Naturalist, 

 has given the results of a large number of experi- 

 ments with butterflies, showing that, if the larvae are 

 not well fed before going into the chrysalis state, the 

 perfect insects developed from them are males ; but, 

 if the larvae are abundantly supplied with food, the 

 perfect insects are females. 3 



In a paper communicated to the Philadelphia 

 Academy, Mr. Gentry details a series of experiments 

 with the larvae of various species of moths, the results 

 of which agree with those obtained by Mrs. Treat 

 with butterflies. Mr. Gentry arrives at the following 

 conclusions : " 1. That males are the invariable result 

 when the larvae are fed on diseased or innutritious 

 food ; 2, That in the fall, when the leaves have not 

 their usual amount of sap, males are generally pro- 

 duced ; 3. That more males are produced late in the 



1 "The Dzierzon Theory," by Baron Berlepsch, pp. 13-36; "Hive 

 and Honey-Bee," by Langstroth, pp. 40-45 ; and other works on the bee. 

 8 Popular Science Monthly, June, 1873, p. 252. 



