435] LARVAE OF THE TENTHREDINOIDEA—YUASA 117 



the beginning of August. In the younger stages, they are gregarious 

 and live in a common nest like many Pamphiliidae, but they spin an 

 individual web when half-grown. There is one generation a year. 



This interesting species was not available for study, and the foregoing 

 definition is abstracted from Konow (1901) and may be found by later 

 students of little value in defining the family. This family, so far as the 

 recorded larval characters are concerned, seems to be closely associated 

 with the Pamphiliidae in possessing the bristle-like subanal appendages 

 and long conspicuous antennae. Future observations, however, may 

 possibly reveal more important characters, not given in the brief synopsis 

 of Konow. 



Family Oryssidae 



Body (Fig. 5) eruciform, grub-like, subcylindrical, slightly depressed, 

 swollen in the middle of the abdomen, tapering at each end; segmentation 

 distinct; annulation obsolete; creamy white, without colored markings; 

 spiracles on prothorax and first eight abdominal segments; thorax increas- 

 ing in size caudad, thoracic legs obsolete; larvapods wanting; fourth 

 abdominal segment largest in diameter, size of segments decreasing rapidly 

 caudad, last segment smallest; suranal process and subanal appendages 

 wanting; head white, compressed cephalo-caudad, circular in frontal 

 contour, narrower than thorax; antennae with a single segment, papilla- 

 like; mandibles tridentate; maxillae and labium vestigial, fleshy, lobe-like, 

 without palpi; ocellarae wanting; larvae parasitic on wood-boring larvae of 

 Coleoptera; pupation in the pupal cells of the hosts. 



The Oryssidae contain six genera and a limited number of species 

 distributed thruout the world. The genus Oryssus alone is represented 

 in the Nearctic region. In former years the family has been associated 

 with the Siricidae, but recently writers are in accord in regarding it as an 

 extremely specialized compact group. MacGillivray (1906) came to the 

 conclusion that "so far as their wings are concerned the presence of the 

 second anal cell in the front wings is the only structure that would place 

 the genus Oryssus in the superfamily Tenthredinoidea" ; The group is 

 not only highly specialized in the adult characters but a recent discovery 

 of the parasitic habit of the larvae isolates these Hymenoptera from all 

 other Tenthredinoidea as a unique class. In fact Rohwer and Cushman 

 (1917) have gone so far as to propose a new suborder, Idiogastra, placing it 

 "intermediate between the suborder Chalastogastra — where adult would 

 place it — and the suborder Clistogastra — with which the larva would ally 

 it." Whether this arrangement is acceptable or not, the fact that this 

 group is remarkably well circumscribed and that it represents the summit 

 of an extremely isolated line of specialization in the Tenthredinoidea 

 can not be doubted. 



