66 INTERNAL SECRETIONS 



3. The Parasitic Castration of Insects. 



Giard (1889 a, 1889 b) about 35 ^^ears ago described very pro- 

 found alterations in insects caused by parasitic castration con- 

 sequent upon an infection taking place very early in the life his- 

 tory of the insect, possibly in the larval stage. Signs of castration 

 are more pronounced in some species than in others. It must 

 be taken into consideration that the dimorphism of the two 

 sexes is developed to a different degree even in related species. 

 When there is a pronounced dimorphism, destruction of the 

 sexual glands was found to cause an alteration of the sex 

 characters. The penis of the male Typhlocyba hippocastani 

 is visibly changed b}- parasitic castration. '' Le caractdre 

 specilique est ainsi profondement atteint," as Giard said. But 

 on the other hand Kopec's objection that all these phenomena 

 observed in insects could also be explained by the unfavourable 

 conditions amid which the animals are placed in regard to 

 nutrition when infected by a parasite, may be valid. 



Further observations on the parasitic castration of insects 

 were made by Perez (1886) on the earth-bee Andrena, infected 

 by another little insect, Sty lops. The sexual dimorphism 

 is very pronounced in Andrena, and the sexual characters 

 are altered by the parasitic castration. The brighter design 

 on the head of the nonnal male tends to become subdued, 

 whereas the design of the infected female becomes brighter. 

 Also the hind legs of the male and female are altered, and the 

 female loses the apparatus necessary for the collection of pollen, 

 normally attached to the hind legs. 



Recently Kornhauser (1919, quoted from Morgan, 1920 b) has 

 made observations on the parasitic castration of the tree 

 hopper, Thelia bimacidata, infected by another insect, Aniphe- 

 lopus. The infected male exhibits many of the characteristics 

 of the female; the degree of the change is mainly dependent 

 on the stage at which the infection has taken place. On the 

 contrary, infected females do not assume any of the charac- 

 teristics of the male. The sexual glands in both sexes 

 are usually degenerate. But Kornhauser observed also that 

 an infected male, which showed considerable sexual change 

 in the direction of the female, contained nevertheless full sized 

 normal testes with many spermatozoa. This observation of 

 Kornhauser's fully bears out those of Courrier on the crab. 



