344 



THE STUDY OF INSECTS 



Fig. 580. — Oryssus sayi; A, female; B, head 

 seen from in front, (from Sharp.) 



suborders of the Hymenoptera. In this suborder the adults (Fig. 580) 

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



and habits of the larva? are those cha- 

 racteristic of the Clistogastra. The 

 distinctive characteristics of the Idio- 

 gastra are those of the single family- 

 included in it. 



Family Oryssid^ 



The Oryssids 



In the shape of the body the mem- 

 bers of this family strongly resemble 

 the Siricidac. They are easily dis- 

 tinguished, however, from all of the 

 Chalastogastra by the anomalous 

 position of the antennae, which are 

 inserted far below the eyes, imme- 

 diately above the mandibles, under a 

 transverse ridge; by the more reduced 

 venation of the wings ; and by the re- 

 markable form of the ovipositor. 



In the form of the ovipositor and 

 in its position when at rest the 

 Oryssidse differ from all other Hymenoptera. For a description of the 

 ovipositor the student is referred to "An Introduction to 

 Entomology " by J. H. Comstock, p. 904. 



The Oryssidse is a widely distributed family, members 

 of it having been found in all of the major geographical 

 regions of the world. But it is a small family, including 

 only a few genera and species. A single genus, Orysstts, 

 is found in North America, of which about a dozen species 

 have been described from this region. 



The adults are very active and are found running over 

 the trunks of trees and" on timber. The larvae were formerly 

 supposed to be borers in the trunks of trees; but it has 

 been shown that they are parasitic on the larva? of Buprestis 

 and probably on other wood-boring larvae. 



The larva of only a single species, Oryssus occidentalis, is 

 known. This is white, subcylindrical, about one-third as 

 thick as long, and legless; but the positions of the legs 

 are indicated by chitinized disks. The mouth-parts are 

 very simple, the labrum, labium, and maxillae 

 merely fleshy lobes, but the mandibles are hard and horn- Cushman.) 

 like; the antennae are tubercle-like and set at the summits of rounded 

 elevations. 



In the pupa of the female (Fig. 581) the terminal portion of the ovi- 

 positor is external and extends over the back the entire length of the 

 body. This long, slender, external form of the ovipositor in the pupa is 

 rather remarkable, especially in view of the very different form it assumes 

 in the adult female. 



Fig. 581. — Pupa 



of Orvssus, female. 



being (After Rohwer and 



