1865.] 343 



be produced by Cynip*. At the end of these tables have been added 

 od. Remarks, containing all the necessary references to the previous 

 publications bearing on the subject, and some new tacts, suggested by 

 the comparison of original specimens, additional descriptions, etc. 



1. The construction of the first of these tables is necessarily imper- 

 fect, owing to the difficulty of finding discriminating characters of easy 

 and general application. Another still more evident cause of imper- 

 fection is, that of many species, only one sex is known. It will be 

 highly desirable to have a new. corrected table published as soon as the 

 accumulation of new facts will require it. Such a table affords the ad- 

 vantage of being the only means for identifying, if not with certainty, 

 at least with some degree of approximation, the species of Cynips taken 

 at large and not bred from galls. A very useful, if not indispensable 

 addition to the table, would have been a full and comparative descrip- 

 tion of all the known species, instead of the existing descriptions differ- 

 ing in the degree of their completeness, often in their nomenclature 

 and seattered in many volumes. I regret that I have not had time to 

 prepare such descriptions. 



The frequent occurrence of phytophagic varieties within the present 

 group has induced me always to add the name of the tree to the name 

 of the species bred from it. The name of the tree and the description 

 of the gall being added to the description of the insect, it will be pos- 

 sible, in most cases, to attain comparative certainty as to the specific 

 identity of the insect, even if its description should only be of average 

 completeness. On the contrary, the insect alone or even the gall and 

 the insect beinir described, without the name of the tree, the identifica- 

 tion may often seem doubtful. Tf a species has been first found on one 

 kind of oak and subsequently on others. I have added the name of the 

 first kiud of oak only, thus showing that the insect bred from that oak 

 represents the type of the species. Tf. for instance, it is once proved 

 that constant differences occur betweeu ('. a, palustris bred from Q. 

 palustris and C. q. palustris bred from Q, tinctoria, the first should 

 be considered as typical. Kntouiologists should be especially cautioned 

 against rashly concluding as to the specific identify of insects bred from 

 two galls, showing a superficial resemblance, but found on different 

 trees. 



In the analytical table No. I, those species which are nearly identi- 

 cal, but occur on different trees, and may thus be considered as phyto- 

 phagic varieties, or incipient new species, are united by brackets. 



I have also introduced a slight change in the nomenclature, which I 

 have to account for. Tn my previous papers, following the example of 



