HYMENOPTERA 



903 



The family Argidae consists chiefly of tropical insects, but a few- 

 representatives of the family are found in this country. Among these 

 are two species of Sterictiphora, the larvae of which occasionally infest 

 sweet potatoes to an injurious extent. 



Suborder IDIOGASTRA* 



This suborder, the establishment of which was recently proposed 

 by Rohwer and Cushman ('17) includes a single small family of rare 

 insects, the Or>'ssidas, which formerly was included in the suborder 

 Chalastogastra. 



The suborder Idiogastra stands intermediate between the other 

 two suborders of the Hymenoptera. In this suborder the adults re- 

 semble the Chalastogastra in the shape of the abdomen ; but the form 

 and habits of the larvae are those characteristic of the Clistogastra. 

 The distinctive characteristics of the Idiogastra are those of the single 

 family included in it. 



Family ORYSSID^ 



The Oryssids 



In the shape of the body (Fig. 

 1 142, A) the members of this 

 family strongly resemble the Siri- 

 cidae. They are easily distin- 

 guished, however, from all of the 

 Chalastogastra by the anomalous 

 position of the antennae, which are 

 inserted far below the eyes, im- 

 mediately above the mandibles, 

 under a transverse ridge (Fig. 

 1 1 42, B); by the more reduced 

 venation of the wings; and by 

 the remarkable form of the ovi- 

 positor. 



In the fore wings (Fig. 1143) 

 the transverse part of vein M2 is 

 wanting; and in the hind wings 

 R4 is wanting; therefore, there 

 are no closed submarginal cells 

 in the hind wings . Th is combina- 

 tion of characters distinguishes 

 the Oryssidffi from all of the Chal- 

 astogastra. In the Oryssidas the 

 first anal cell of the fore wings is preserved, in which respect the 

 members of this family differ from all of the Clistogastra. 



*Idiogastra : idio (Wtos), distinct; gastros (yaffrpds), the belly. 



Fig. 1 1 42. — Oryssus sayi; A, female; B, 

 head seen from in front. (From 

 Sharp.) 



