1909.] 



NATURAL SCIENCES OF PHILADELPHIA. 



31 



strengthened by the fact that it occurs as a distinct sclerite only in the 

 segments which bear functional wings. Thus it seems to be absent 

 in the prothorax of all the insects which the writer has studied, and no 

 traces of it are to be found in the metathorax of the Diptera, although 

 it is well developed in the mesothorax of these insects. 



Since the mode of life is the same among insects and myriopods, and 

 as the legs of both are used in the same manner, it is but natural that 

 there should be a very marked convergence in the structure of these 

 organs. This, however, is not sufficient ground for attempting to 

 change the terminology applied to the segments of the insect leg, as 

 Verhoeff, '03-'04, has done. Even if it could be demonstrated that 

 the joints of the insect leg can be homologized with corresponding- 

 ones in the myriopods, the terminology for the leg segments of the 

 myriopods should be adapted to that of insects, as the latter has- 

 the right of priority and of widespread acceptance. 



Fig. 15. Fig. 16. 



Fig. 15. — Nepa. — Ventral view showing half of the sternum and the corre- 

 sponding pleuron of the meso- and meta-thorax and the first three abdominal 

 segments. The flap-like mesothoracic epimeron {EM") is raised up and bent 

 forward to show the metathoracic epimeron (EM'") which lies under it and 

 was overlooked by Heymons. The corner of the metathoracic epimeron (EM'") 

 is likewise slightly raised to show the first abdominal segment which is hidden 

 by the epimeron, and does not appear in Heymons' figure of Nepa (fig. 16). 



Fig. 16. — Heymons' figure of Nepa, slightly modified. The dotted lines indicate 

 the region corresponding to that shown in fig. 15. 



Of the leg segments only the coxa and trochanter need be here con- 

 sidered. The coxa is frequently divided into two regions, as has been 

 previously described. Verhoeff's, '03, term eucoxa (fig. 3, C y ), applied 

 to the anterior coxal region, seems preferable to Walton's, '00, "coxa 

 genuina," but for the posterior coxal region Walton's term meron has 



