Effects of Castration in Insects 40 7 



they have satiated their queens and the young broods which are 

 continually hatching from her eggs. Marchal ('97) has called 

 attention to this condition in the wasps, and it has long been 

 known to obtain in ants and the social bees, though the causal 

 connection between the protracted immaturity of the ovaries 

 in adult workers and their primary function as nurses had not 

 been sufficiently emphasized. The form of castration which is 

 thus produced is, however, not necessarily permanent. If the 

 trophic status of a colony becomes highly favorable, or if the queen 

 dies, the ovaries of one or of a number of the workers may undergo 

 active growth and produce eggs capable of normal development. 

 In such cases the workers may be said to usurp or to supplement the 

 function of the queen, but owing to the fact that the adult insect 

 cannot modify its external characters, there is no visible differ- 

 ence between the sterile and fertile workers, except in the size 

 of the abdomen, and even this may be so slight as to escape 

 observation. The primary cause of nutricial castration is to be 

 sought m the instmcts of the mdividual itself, whereas alimentary 

 castration would seem to be attributable to the instincts of the 

 individual's living enviroment, i.e., to its nurses. This distinc- 

 tion, however, is probably more apparent than real, since as I 

 have suggested in a former paper ('07), it is possible that the 

 worker larva is from the beginning an organism predisposed to 

 assimilate only a portion of the nourishment with which it is 

 provided by its nurses. The growth and development of the 

 larva obviously does not depend on the amount of food admin- 

 istered to it but on the character and rate of operation of its 

 assimilating mechanism. A larva may be very voracious, but 

 its tissues may be constitutionally unable to appropriate more 

 than a limited portion of the food which enters its alimentary 

 tract. The administration of highly assimilable food, as in the 

 case of the ''royal jelly" which is fed to the larval queen bee, may 

 be, as I have maintained ('07), primarily for the purpose of 

 accelerating the development of her ovaries, and the secondary 

 characters of this insect, which are mostly of an abortive charac- 

 ter (smaller sting, shorter wings, smaller hind legs) may be the 

 result of this development. 



