2 Rev. T. A. Marshall's monograph of 



to entomological science from the assistance of such a 

 host of well-placed observers has often been pointed out. 

 A minute account of the anatomy and physiology of 

 these insects is beyond the scope of the present essay, 

 and must be sought in the works of Gravenhorst, Nees 

 von Esenbeck, Curtis, Westwood, &c. But such par- 

 ticulars as are necessary to distinguish the Braconidce 

 from other parasitic Hymenoptera, and to understand 

 their descriptions, may here be concisely stated. 



TheBraco7iidce, Ichneumones adsciti, or supplementary 

 Ichneumons, are closely related, in structure and habits, 

 to the genuine Ichneumons. They consist of about 

 twenty- six groups or subfamilies, connected by a few 

 common characters, and yet so widely separated by 

 others as to show that links in the series are missing, 

 and to render their linear arrangement impracticable. 

 They are, however, all distinguished from the true 

 Ichneumons by wanting the exterior discoidal transverse 

 nerrure in the fore wings ; and by having the first 

 cubital areolct generally, though not always, separated 

 from the prcediscoidal ; in the Ichneumons these two 

 areolets are never distinct. With the exception of one 

 subfamily, the Aphidiides, they are further remarkable 

 for the absence of a real articulation between the 2d 

 and 3d abdominal segments. In the language of Strauss 

 Durckheim, these two segments are united either (1) by 

 juxtaposition without imbrication, in which case a suture 

 is visible, but there is no joint to permit the flexure of 

 the abdomen ; or (2) by coalition, the segments being 

 soldered together, without any trace of a suture, and 

 equally without power of movement. When the junction 

 of these two segments is visible, it is called the suturi- 

 form articulation. In many descriptions (as in those of 

 Microgaster by Wesmael) the 2d and 3d segments are 

 spoken of as one ; but this is inconvenient, and is not 

 here adopted. The suturiform articidation affords the 

 means of referring to the Braconidce certain forms like 

 Dimcris and Chasmodon, wdiich, having no wings, would 

 not otherwise be easily recognised. Imperfect articula- 

 tion of the segments is further developed in some of the 

 subfamilies, and reaches its maximum in the Chelonides, 

 most of w'hich have the three segments that are visible 

 from above soldered together. The Aphidiides, on the 

 contrary, have all the segments loosely articulated, and 

 are able to bend the abdomen beneath them so as to 



