906 AN INTRODUCTION TO ENTOMOLOGY 



In this suborder the intermediate region of the body is not merely 

 the thorax but includes also the first abdominal segment, only the 

 tergxim of which is preserved in the adult. This 

 is known as the median segment, or the propodeum 

 and can be identified by its spiracles, the third 

 pair of this region of the body. It should be re- 

 Fig. 1 147. membered that the thorax bears only two pairs 

 of spiracles (See page 115). From the above it 

 follows that what appears to be the first abdominal segment in the 

 Clistogastra, and which is usually so-called, is really the second. 

 In the Clistogastra the ovipositor and its sheath are composed of 

 the same morphological elements as are those of the sawflies described 

 on an earlier page ; but these parts differ greatly in form in different 

 members of this suborder. In some the ovipositor is a boring instru- 

 ment by means of which deep holes are made into trees and eggs 

 placed in these holes ; in others it is used for thrusting the eggs into 

 the bodies of other insects; and in still others it is modified so as to 

 form a sting with which poison glands are connected. 



TABLE OF FAMILIES OF THE CLISTOGASTRA* 



A. With well-developed wings. 



B. Hind wings without an anal lobe.f 



C. No erect scale or node between the gaster and the propodeum. 



D. The costal cell of the fore wings eliminated by the coalescence of the 

 costal and subcostal veins, except in the case of two or three rare genera. 

 The venter is membranous and has in dried specimens a longitudinal 

 fold. 



E. The transverse part of vein M2 of the fore wings wanting, causing 

 the union of cells Mi and ist M2 (Fig. 1 148). 



F. The abdomen not very long and slender and strongly com- 

 pressed, p. 916 BRACONIDiE 



FF. The abdomen very long, slender, and strongly compressed. 



(The genus Pharsalia) p. 917 Ichneumonid^ 



EE. Cells Ml and ist M2 separated by the transverse part of vein Mj 



(Fig. I 152). p. 917 ICHNEUMONID^ 



DD. The costal cell of the fore wings present. The venter chitinized. 

 E. Abdomen borne on the dorsal siu-face of the propodeum far above 

 the middle coxas. 

 F. The transverse part of vein M2 present in the front wings, which 



have at least two closed submarginal cells, p. 918 AuLACiDiE 



FF. The transverse part of vein M2 wanting in the front wings, 

 which do not have two closed submarginal cells, p. 919 



GASTERUPTIONIDiE 



EE. Abdomen borne between the hind coxag, or on the end of the pro- 

 podeum slightly above them. 



F. The transverse part of vein M present and situated close to the 

 stigma. 



*This table of families of the North American Clistogastra is compiled from a 

 table of the families of the Clistogastra of the world prepared by Professor J. 

 Chester Bradley and kindly placed at my disposal. 



fin the hind wings of the insects belonging under this category neither the 

 second anal furrow nor the axillary excision is present, but there is sometimes 

 present a weak preaxillary excision, more rarely (some genera of Braconidae) 

 a pronounced notch, but never forming a deep slit. See also footnote on page. 909. 



