GENERAL CHARACTERS. 7 



i.e. connected with the thorax by a more or le.«is slender petiole or 

 footstalk. The terms " subsessile" and " subpetiolate" are moditica- 



tions of the sessile and ])eti()late forms and 

 are characters not only difficult to describe 

 by word or figure, but unsatisfactory and 

 })erplexing. In the Heterogyna the petiole 

 is either scale-like or nodose, often binodose, 

 and in the Tubulifera the number of visible 

 abdominal segments is usually reduced to 

 three, the remainder being modified into a 

 slender retractile tube, which is generally 

 concealed. The place of insertion of the 

 abdomen is at the apex of the metathorax, 

 except in the anomalous family Evaniid^e, where it is inserted on the 

 disk or very near the base of that segment. In the Ichneumonida? 

 the situation of the spiracles on each side of the first segment is fre- 

 quently used as a character for separating some of the subfamilies. 

 In the females of Hymenoptera the abdomen is furnished with an 

 instrument applied in the different groups as a saw, borer or sting, 

 protected by sheaths and called the ovipositor, which is often more 

 or less exserted, sometimes to a great length in certain genera of 

 Ichneumonidae. 



Fia 



Fig. 8. 



Professor Westwood, in his " Introduction," etc., vol. ii, following 

 chiefly the views of Latreille, divides the Order into two Sections, 

 viz. : Terebrantia and Aculeata, the former having the abdomen 

 of the females furnished with an instrument employed as a saw or 

 borer for depositing the eggs ; and the latter having the abdomen of 

 the females (and workers) armed with a sting connected with a i)oison 

 reservoir, the antennae of the males 13-jointed, and of the females 

 12-jointed. 



The Terebrantia is then divided into two subsections, the first, 

 termed the Phytiphaga, having the abdomen sessile, hiding the base 

 of the posterior legs, the larvae with a well developed mandibulated 

 mouth, feeding upon vegetable matter, and containing the families 

 Tt'uthrcdin'uUe and Uroceridcc. The second subsection, the Ento- 

 moj)haga (Pupivora Lair.), having the abdomen attached to the 

 thorax by a portion only of its transverse diameter, tlu' larva) with 

 slightly developed mandibulated troi)hi, and for the most part feeding 



