20 



PROCEEDINGS OF THE ACADEMY OF 



[Jan., 



forms an articulation with the coxa, has been termed the coxal process. 

 These'processes will be discussed more at length in a later article dealing 

 with the comparative myology of insects. 



The Epimeron. — It is generally taken for granted that the epimeral 

 and episternal regions of the thorax are not subdivided into smaller 

 sclerites, but a glance at the mesothorax of Cicada (fig. 5) and Tipula 

 (fig. 7) or the metathorax of Myrmeleon (fig. 4) and Chrysopa (fig. 3) 

 will readily convince one that this is an error. 



To illustrate, let us examine the thorax of the widespread insect 

 Chrysopa. For this purpose Chrysopa vulgaris is preferable to the 

 somewhat commoner form Chrysopa perla, as the black bars and 

 markings upon the thorax of the latter insect tend to obscure the 

 sutures between the subregions. 



In the epimeral region of Phassus (fig. 6), and most winged insects 

 as well, one can readily find an elongate plate embedded in the softer 

 cuticule directly under the posterior portion of the wing (EM C ). This 

 sclerite doubtless corresponds to the plate which Lowne, '90, desig- 

 nates as the "costa" in the blow-fly. The term costa, however, has 

 been applied to one of the wing veins, and this usage has been every- 

 where adopted. It would, therefore, seem preferable to substitute 

 the expression costal sclerite in referring to the above mentioned 

 plate. 4 The costal sclerite bears an internal process, which serves as 



Fig. 3. 



Fig. 3. — Chrysopa. — Lateral view of right flank. 



antennae partially removed. 

 Fig. 4. — Myrmeleon. — Side view of right flank. 



antennae partially removed. 



Fig. 4. 

 Abdomen, legs, wings and 



Abdomen, legs, wings and 



the point of insertion for the epimeral wing muscles. This process 

 may be termed the endocostal process. Behind the costal sclerites 

 there frequently occurs a smaller sclerite which likewise serves as an 

 attachment for the epimeral muscles. This will be spoken of as the 



4 Snodgrass, '08, terms this sclerite the "postepimeron," but since the plate 

 in question is normally " supraepimeral " rather than "postepimeral," Lowne's 

 term, slightly modified, has been here retained. 



