410 William Morton Wheeler 



opment exhibited by the large breeding crabs." This same con- 

 dition was previously observed by Faxon ('85) in male crayfish 

 belonging to the American genus Cambarus. Of course, the three 

 stages distinguished by Smith are separated by moults. Ob- 

 viously we have here a condition like that observed in many male 

 fishes, amphibians and birds, which lose their secondary sexual 

 characters during the seasons when they are not breeding. Smith 

 regards the phenomenon as "obviously parallel to the 'high and 

 low dimorphism,' so common in lamellicorn beetles," but this 

 is a mistake, as 'Cunningham ('08) has shown, for we are here 

 confronted with a case of seasonal sexual dimorphism. Nothing 

 comparable to the condition described above is seen in insects, 

 for the reason that these animals either do not mature their 

 gonads till after they have attained their fixed and final imaginal 

 instar, or if they become sexually mature as larvae or pupae (neo- 

 tenic and paedogenetic aphids, cecidomyids, chironomids, etc.) 

 they do not develop beyond this stage. It is not improbable, 

 however, that insects which live several years in the adult stage 

 and have seasons of sexual activit)' alternating with seasons of 

 infertility, may exhibit great periodical changes in the size and 

 development of the reproductive organs. I have been unable to 

 find any observations on this subject in the entomological litera- 

 ture. 



5- Individual Parasitic Castration. 



I 



The first zoologist fully to appreciate the importance of para- 

 sites in suppressing the reproductive function and in incidentally 

 affecting the somatic characters of their hosts was Giard. He 

 published some twenty papers ('69-'o2) on a great variety of 

 cases which he observed not only among animals but also among 

 plants. The cases to which he devoted most attention were the 

 decapod Crustacea, especially species of Stenorhynchus, Portunus, 

 Carcinus, Cancer, Platyonychus, Eupagurus, Palsemon, Gebia and 

 Hippolyte, which are infested with extraordinary cirriped and 

 bopyrid parasites of the genera Sacculina, Portunion, Bopyrus, 

 Probopyrus, etc. Within more recent years these studies have 



