THE THORAX. 73 



the back (dorsum), with the exception of the scutellum lying between 

 the elytra. 



The following Orismology of Kirby and Spence is much more 

 diffuse : 



The trunk (truncus) is divided into two chief parts the anterior 

 bearing the anterior legs, called manitruncus, and the posterior, ali- 

 truncus, upon which are placed the four posterior legs and the wings. 



The upper side of the manitruncus is distinguished as the prothorax, 

 and its broad lateral margin as border (prct) ; the patagia, two cor- 

 neous scales densely covered with hair in the Lepidoptera ; the um- 

 bones, two moveable thorns on the sides in Acrocinus longimanus ; and 

 the pliragma, the posterior margin descending in front of the alitrunk. 

 The under side is called antepectus, the central prominent ridge of which 

 is called proslernum, and the antefurca, which is an internal process 

 for the insertion of the muscles. 



The alitruncus has the following divisions and parts: the first 

 division upon which the anterior wings are placed is called above the 

 wesothorax, or is divided into the collare, particularly visible in the 

 Hymenoptera, it appears to be wanting in insects with a distinct 

 manitrunk, the prophragma, a thin partition which descends from 

 the anterior margin of the mesothorax into the cavity of the trunk, and 

 separates the anterior segment from the intermediate one. The clor- 

 solum is that portion of the superior surface which lies between the 

 collare and scutellum, upon which are found the wing-sockets (ptcro- 

 pega). These cavities are, in the Hymenoptera, covered by two small 

 scales (tegulce). The scutellum, a triangular corneous piece placed 

 behind the dorsolum, and between the superior wings, serves as a point 

 of insertion of the elytra. The under side of the anterior division of 

 the alitrunk is called mcdipectus, in which is again distinguished the 

 peristethium, or anterior central part lying in front of the sockets of 

 the intermediate legs (the same part of Knoch) ; the scapularia, placed 

 exteriorly next to the peristethium; the mesosternum, the prominent 

 central ridge of the medipectus ; and the medifurca, a forked process 

 of the interior surface of the medipectus. The superior surface of the 

 posterior division of the trunk is called metatkorcue. Upon this is 

 found the mesophragma, a separating partition running parallel with 

 the prophragma, and descending from the anterior margin of the 

 metalhorax ; the post-dor solum, the intermediate piece between the 

 mesophragma and post-scntelliim ; the post-scutellum, that piece which 



