OF WASHINGTON, VOLUME XVII, 1915 



177 



event, they are merely secondary to the general functions of the 

 hypopharynx. The main movements of the latter organ are 

 produced by the mental-tentorial muscles B (pi. 19, fig. 7> and 

 the mental-zygomatic muscles A. These, when acting simul- 

 taneously, cause the retraction of the entire labium and act- 

 ing independently cause the elevation and depression of the same. 



Fig. 1. Papnipema nitela Guenee. 



Inasmuch as the mental arms are often very thinly diilinixcd 

 and hence more or less elastic, it is not improbable thai a slight 

 inward and downward movement be imparted to the maxillulse 

 by the play of the muscles /' and f", although these are primarily 

 intended for dilation of the threadpivss (pi. 19, fig. 8) and various 

 movements of the spinneret S (pi. 19, fig. 7). 



