1909.] 



NATURAL SCIENCES OF PHILADELPHIA. 



21 



posterior costal sclerite (EM 2C ). It is usually very small and relatively 

 unimportant. 



In the metathorax of Chrysopa and Myrmeleon, and in the mesotho- 

 rax of Cicada, etc., the epimeron is distinctly divided into an upper 

 and lower portion. The upper region will be referred to as the anaepi- 

 meron 5 or anepimeron (fig. 3, EM & ) and the lower region may be termed 

 the kataepimeron or katepimeron (EM k ). In the Raphidians, the 

 suture between the anepimeron and katepimeron is partly obliterated, 

 and in many other insects all traces of it have disappeared. In 

 Phassus scliamyl (fig. 6), the upper portion of the epimeron is mem- 

 branous, thus suggesting that in other insects the anepimeral region 

 may have originally arisen as a softening of the chitin, to give greater 

 freedom of motion to the wing, and thus become differentiated from 

 the remainder of the epimeron. 



In the Muscinse, there is an arching of the mesothorax and a shifting 

 forward of the sclerites — probably 



xx 



Fig. 5. — Cicada. — Lateral view of right 

 flank. Abdomen, legs, and wings 

 shortened. 



the result of muscular tension — 

 so that the upper region of the 

 epimeron (EM & ) is bent forward 

 and lies upon the episternum 

 (fig. 8). It would appear that 

 Lowne, '90, and other dipterolo- 

 gists have not been aware of this 

 fact, for Lowne, Hewitt, '07, and 

 a number of others mistake the 

 anepimeron (EM a ) for the epis- 

 ternum and consequently designate the katepimeron (EM^) as the 

 entire epimeron. A comparison with one of the Tipulidse — in which 

 group the sclerites are in their normal positions — readily shows the 

 error of such a homologization. In the Tipulidse, and less distinctly 

 in the Ephemeridse, the pleurophragmite (or lateral region of the 

 postscutellar phragma) is so closely connected with the pleuron that 

 it appears to be a part of the pleural region (fig. 7, N 4 hs)', but, with 

 the "parapleure" of the Coleoptera, it should be classed as a portion 

 of the posts cutellum. 



Connected with the lower portion of the epimeron in Chrysopa and 

 a number of other insects is a sclerite termed the meron (fig. 3, C 2 ). 



6 In an earlier publication (Crampton, '08) the term hyper- and hypo-epimeron 

 were employed to designate these regions, but, upon further consideration, it 

 has seemed preferable to substitute the designations ana- and kata-epimeron, 

 which are not so confusingly similar as the former terms. 



