134 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



area which may well be called the parasternum for descriptive 

 purposes. Between the sternal lines extends a transverse line, 

 the eusterno-sternellar line (est.stl), separating the eusternum 

 from the sternellum. In some larvae it is continuous with the 

 sternal line, in others perpendicular to it, and probably more or 

 less represents the same line, but for the sake of the discussion 

 it is considered separately. It is defined by muscles to the pos- 

 terior notch pn-est.stl. That part of eusternum extending dor- 

 sad to the sternopleural suture in front of the coxal lobe often 

 becomes a separate area in the thorax. 



All the ventral areas like the corresponding dorsal ones, are 

 protuberant ventrally, forming the ampulla. Several muscles 

 (i-est) extending from the eusternal region posteriorly to the 

 inferior cunea and several (i-stl) from the sternellar region ante- 

 riorly to the inferior cunea are not considered as defining any 

 definite areas or regions, but are of importance in contracting the 

 ampullae and producing its bilobed form in many larvae. 



A comparison of two other types of larvae, the Cerambycinae 

 and the Prioninae, with that of the Lepturinae shows that in both 

 these forms the pleurum is not protuberant and only one of the 

 short tergopleural-sternopleural muscles (tp-sp) is present. Like- 

 wise the tergopleural suture is very indistinct, especially in Cer- 

 ambycinae forms. By the stress being removed from this suture 

 and distributed more generally over the spiracular area the 

 region around the spiracle has assumed on ellipitical form, lying 

 partly in the pleural zone and partly in the spiracular area. This 

 to some extent acts as a substitute for the elastic effect of the 

 pleural lobe which is very prominent in Leptura forms, indistinct 

 on Prioninae larvae and still less evident on Cerambycinae types. 

 Thus this tubercle or lobe becomes distinct or obsolete according 

 to the position and strength of the sternopleural-tergopleural 

 and other pleural muscles. In the last three abdominal segments 

 of the Cerambycinae and Prioninae larvae the same development of 

 pleural region and lobe is present as in all segments of the Lep- 

 tura abdomen. Again in Prioninae the postcoxal line pushes 

 downward shortening coxal lobe which is entirely lost in the 

 Cerambycinae as the muscles indicate; those which define the 

 postcoxal line (tp-pcx and s-pcx) having nearly the same attach- 

 ment as those defining the coxal lobe. In the Cerambycinae 

 the sternopleural suture is not defined anteriorly, thus presternum 

 and pleurum are fused. 



THE THORACIC STRUCTURE 



The transition from the abdominal to the thoracic segments is 

 a gradual one and can best be seen by comparing the integument 

 from which all the muscles have been removed with another 

 specimen with all the muscles in situ. 



