Effects of Castration in Insects 397 



form of castration is not sharply marked off from the two preceding 

 but mav be made to include them, since both ahmentary and 

 nutricial castration can be suspended during the hfe time of the 

 individual and normal reproduction supervene. 



3. Parasitic castration. This term was first introduced bv 

 Giard ('87, etc.) in a series of studies on Crustacea. It refers to 

 the suppression or destruction of the gonads by parasites. By 

 enlarging the scope of Giard's definition we can distinguish two 

 forms of parasitic castration: 



A. Individual parasitic castration, which is induced in certain 

 organisms when they contam parasites, and 



B. Social parasitic castration, which occurs in ants when one 

 colony in becoming parasitic on a colony of a different species 

 eliminates the sexual individuals of its host. 



A number of illustrations will bring out the fundamental 

 resemblances between -these different methods of suppressing the 

 reproductive function and the resulting modifications of the 

 somatic characters of the individual or of their equivalents in 

 animal societies. 



/. Surgical castration. 



The pronounced modifications of the secondary sexual charac- 

 ters observed in vertebrates, especially in birds and mammals, 

 from which the gonads have been removed during early life, or 

 in which these organs have become diseased, have led some inves- 

 tigators to look for corresponding modifications in the secondary 

 sexual characters of insects subjected to a similar operation. 



One observer, Hegner ('08), has succeeded in castrating the 

 embryos of a chrvsomelid beetle (Calligrapha multipunctata) by 

 removing the very young sex-cells as soon as they are segregated 

 in the protoplasmic accumulation at the posterior pole of the egg 

 during the formation of the blastoderm. Although Hegner's 

 experiment, which consisted in pricking the chorion at the pos- 

 terior pole and allowing the sex-cells to flow out, was successful 

 to the extent of demonstrating that the embryo may continue its 

 development after the operation, nothing but a few young larvcie 



