HYMENOPTERA — SAW-FLIES, ETC. 



167 



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

 the propodeuni (f/ 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-, meso-, and nieta-thorax. If the front and 

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

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

 coxae away from the hind coxa3, 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 (^.r/., in a dried specimen by 



'ig. 157. — Thorax of a saw-fly : dorsal surface — 

 i.e., as seen from above. (Sketch by Re^•. F. 

 D. Morice. From ' Entomologist's Monthly 

 Magazine.') 



-Lateral or side view of 

 fin- 157. 



pushing it roughly downwards), the propodeum always remains with 

 the thorax. 



"In fig. 157, 7?, h, 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. 



" Eegarding 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. We commence with them partly 



