150 FAMILY CYNIPIM. 



have a large central cavity ; inhabited by the inquilines 

 it becomes enlarged, swollen, and many-celled, the 

 cells being separated by partitions of spongy cellular 

 matter. Lastly, the species of the third section are 

 true animal parasites, living, like the Ichneumonidds, 

 on other insect larvge, chiefly Diptera and Homoptera. 



The modes of reproduction in the Gynipidss show 

 some highly interesting and instructive features. So 

 far as our present knowledge extends, the parasitic 

 species reproduce themselves in the normal way by 

 males and females ; and this is also the case with 

 many gall-making and inquiline species. But we find 

 also among them undoubted evidence of partheno- 

 genetic reproduction, either complete or incomplete. 



The genus Ceroptres apparently furnishes an ex- 

 ample of both kinds. Thus Mayr bred over 600 

 specimens of C. arator, Htg., without finding a single 

 male among them ; of C. cerri Mayr reared ninety-eight 

 females and only four males (Verh. z.-b. Ges. Wien, 

 xxii, p. 672). In one small lot of bedeguar galls I 

 found no great disparity between the sexes, although 

 the females were certainly more numerous, but from 

 other breedings the males have been in the propor- 

 tion of one male to over 100 females. Adler (B. B .Z., 

 p. 217), from extensive and careful observations, finds 

 also that the males, in proportion to females, are very 

 rare. He has furthermore proved by direct observation 

 that Rhodites rosde can produce fertile eggs without being 

 fertilized. Among the oak-gall flies complete partheno- 

 genesis among single-brooded species is common ; in 

 fact, not one single-brooded species is known to have 

 a male, parthenogenesis among such being universal, 

 e.g. Andricus quadrilineatus , A. albopunctatus, &c. 



Still more remarkable is the occurrence of alterna- 

 tion of generation among the gall-making species of 

 species having a bisexual spring generation reproduc- 

 ing sexually, followed by an autumnal unisexual brood, 

 reproducing parthenogenetically. Besides this physio- 

 logical distinction between the two broods, there are 



