AMERICAN IIYMENOPTERA. 85 



A MONOGRAPH OF THE GEXIJS SYIWEROUS Haitig. 

 BY C. P. GILLETTE. 



I find ill the college collection, as a result of our rearings for the 

 past three years, a considerable number of Synergus species, some of 

 which are new to science. As I have the original descriptions and 

 also representatives of all the North American species, and as many 

 of the descrij)tions are inaccessible to students of Entomology, I have 

 concluded to bring together, in one paper, descriptions of all the 

 species, with au epitome of our present knowledge in regard to their 

 habits. 



Ill this connection I wish to thank Mr. W. H. Ashmead who has, 

 in past years, determined several species of Synergus for me, and 

 who has sent me types of those species described by himself. 



The members of this genus are all Intpiilines, or guest-Hies, in- 

 habiting the galls of the oak-infesting Cynipidse. Although true 

 parasites, so far as the gall within which they develop is concerned, 

 they are not parasites in the ordinary acceptation of that term as 

 applied to insects, as they do not attack the true gall producer. 

 They are vegetable feeders and not flesh consumers. 



Tiiis genus is not a large one as at present known in this country. 

 In Europe there are 31 described species of Synergus, while, includ- 

 ing the eight new species in this paper, there have been but 24 spe- 

 cies described from North America. As yet none of these 55 species 

 are known to occur on both sides of the Atlantic. 



The bibliography given in this paper is largely copied from Dr. 

 De Dalla Torre's " Catalogus Hymenopterorum." 



SY!VEROUS. 



Hartig:, Zeitscbr. f. Eiitmn. ii, 1840, p. 186, n. 13. 



This genus is readily se})arated from all other Hymenoptera by 

 the closed marginal cell of the wing, the coarsely striated face, the 

 fluted petiole and first abdominal segment, and by the large second 

 abdominal segment, which occupies nearly or quite all of the abdomen. 



The species may all be separated into three natural groups as 

 follov.'s : 



Antennffi of feinaU' 1.3-.jointec] Group I. 



AntPiiiia' of female 14-,joiiitcd Group II. 



AntennsK of female 15-joiiited Group III. 



TRANS. AM. ENT. SOC. XXIII. MARCH. 1896. 



