HYMENOPTERA 



90'i 



the two parts of the sheath (third gonopophyses) arise from the apices (Fig. 

 1 145, Sh). Shortly cephalad of the origin of the lance and lancets the latter en- 

 ter the groove of the former, the complete ovipositor as thus formed extending 

 cephalad in an inverted position enclosed within a membranous sac, probably in- 

 vaginated intersegmental skin, into the mesothorax, where it is coiled, and re- 

 turning upon itself continues caudad in its normal position and enters the base of 

 the sheath (Fig. 1145J. 



The Oryssid^ 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, Oryssus, 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 run- 

 ning over the trunks of trees and on timber. The 

 larvEe were formerly supposed to be borers in the 

 trunks of trees; but it has been shown by Burke 

 ('17) that they are parasitic on the larvse of Bnprestis 

 and probably on other wood-boring larvae. 



The larva of only a single species, Oryssus occi- 

 dentalis, 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, la- 

 bium, and maxilla being merely fleshy lobes, but 

 the mandibles are heavily chitinized; the antennae 

 are tubercle-like and set at the summits of rounded 

 elevations. 



In the pupa of the female (Fig. 1146) the termi- 

 nal portion of the ovipositor is external and ex- 

 tends over the back the entire length of the body. 

 Referring to this, Rohwer and Cushman ('17) state as follows: 



The reason for the formation in the pupa of the long external ovipositor is in- 

 explicable, and its reduction to the form existirg in the adult is equally inex- 

 plicable. This is rendered all the more difficult to understand by the fact that in 

 the prepupa the ovipositor is coiled as it is in the adult, while in the pupa it forms a 

 simple loop in the thorax. 



Fig. 1 146.— 



Pupa of Orys- 

 sus, female. 

 (After Roh- 

 wer and Cush- 

 man.) 



Suborder CLISTOGASTRA or APOCRITA* 

 Parasitic Hymenoptera, ants, wasps and bees 



This most striking characteristic of this suborder is the fact that 

 what appears to be the first abdominal segment, but which is really 

 the second, is greatly constricted forming a slender petiole or waist 

 between the larger portion of the abdomen and the alitrunk or wing- 

 bearing region of the body (Fig. 1147). 



*The name Clistogastra is the one most commonly applied to this suborder 

 and for that reason is used in this work; but some authors use Apocrita, which is 

 really the older name. The etymology of these names is as follows: Clistogastra: 

 clistos (xXeto-ros), closed; gaster (yasT-qp), the belly. Apocrita: apocritos 

 (dTTOKptTos), separated; apo (otto), from, crino {kpIvu), to separate. 



