HYMENOPTERA SAW-FLIES, ETC. 



167 



the meta-thorax includes the areas/in fig. 157, o and m in fig. 158 ; 



the propodeum (g in both figures) is an originally abdominal seg- 

 ment, transferred to the thorax in pupation. 

 " The thorax of a saw-fly can easily be broken up into its three 

 constituent parts of pro-, mes'o-, and meta-thorax. If the front and 

 middle coxa? are seized in two pairs of pincers and pulled apart, the 

 pro- and meso-thorax part company. Similarly, by tearing the middle 

 coxpe away from the hind coxte, the meso-thorax can be separated 

 from the meta-thorax. The so-called propodeum, though theoreti- 

 cally an abdominal segment, is so firmly attached to the meta-thorax 

 that when the abdomen is broken off {e.g., in a dried specimen by 



Fig. 157. Thorax of a saw-fly : dorsal surface 

 i.e., as seen from above. (Sketch hy Rev. F. 

 D. Morice. From ' Entomologist's Monthly 

 Magazine.') 



Fig. 158. Lateral or side view of 

 fig. 157." 



pushing it roughly downwards), the propodeum always remains with 

 the thorax. 



"In fig. 157, h, fi, the ' cenchri ' are two singular organs with some 

 resemblance to little tegulae. They are always present in Tenthred- 

 inidse, but I cannot find that their function has as yet been discovered. 

 They belong to the meta-thorax, and mark its base. 



" Regarding the neuration of a saw-fly's wing, the first thing to be 

 done is to realise the course of the longitudinal nervures = the 

 ' veins,' the thick single lines. It will be seen that they are much 

 longer than the transverse = the 'nerves.' They are also more 

 uniform throughout the whole group, and much less liable to vary 

 abnormally in individual specimens. "VVe commence with them partly 



