10 INTRODUCTION. 



The thorax consists of three distinct sections : — That nearest 

 tlie head is the prothorax, bearing the front pair of legs ; the middle 

 section is the mesothorax, bearing the intermediate pair of legs 

 and the anterior pair of wings ; the last section is the metathorax, 

 bearing the hind pair of legs and the posterior pair of wings. The 

 disc of these sections is known as the notum, their sides as the 

 pleura), and the lower surface as the sternum. The prothorax is 

 very short, usually transverse, extending laterally to the radices 

 of the wings ; its pleurae bear grooves, in which the upper side 

 of the front femora rests, and their margins are known as the 

 epomite. The mesothorax is usually as broad as or a little broader 

 than the head, and is divided into two distinct sections, termed 

 the scutum or mesonotum, which is produced into the prominent 

 and often convex scutellum ; two impressed lines are frequently 

 found couvergijig from the apex of the mesonotum to its disc, 



Fig. 2. — Metathorax of an Iclineumon. 



1, basal ai*ea ; 2, areola; 3, posterior or petiolar area; 3ff, postero-inter- 

 niedial area;; 3/', postero-external area;; 4, external areiB ; 5, dentiparal 

 areoe; 6, spiracular area;; 7, lateral or ijleural arete ; 8, jiixta-eoxal arett ; 

 9, spiracles. 



near the scutellum, and are collectively known as the notauli. In 

 contradistinction to these, the mesosternum is often similarly 

 impressed on either side at its junction with the mesopleuroe, and 

 these impressions are termed the sternanli. Tlie scutellum is 

 much smaller than the disc of the mesonotum and is situated at 

 the base of tlie mesothorax, between the hind pair of wings. It 

 is more or less convex, nearl}"^ always triangular, with erect 

 pilosity ; and at its apex is a small prominence, designated the 

 postscutellum. It will be noticed that the postscutellum forms 

 the centre of a transverse, almost linear band, which laterally 

 bears the hind wings. This is said to be the true metanotum, 

 which is not referred to in descriptions. The convex area between 

 it and the abdominal petiole is considered to be the true first 

 abdominal segment, and is superincumbent upon the true metano- 

 tum, which is divided from it obliquely along the sides by a carina 

 and extends back to and bears the hind coxse. This portion is 

 termed the propodeum or median segment by Bingham, Saunders, 



