20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



and the parietal can be seen to merge with the hypopharyngeal ridge, 

 which is apparently formed jointly by the epipharynx and the hypo- 

 pharynx. In effect, the hypopharynx has contributed the median sur- 

 faces of each ridge and the area in the floor of the pump between the 

 ridges. The dorsal dilators (is) of the salivarium usually arise on 

 these ridges, indicating that at least that much is hypopharynx. 



The dorsal wall of the pump varies greatly throughout the order 

 in the particular arrangement of its dilating muscles, but shows in- 

 teresting consistency in the relative development of the true dilators 

 of the pharynx and the dilators of the cibarium. Moths beginning 

 with the Tineidae were examined, but no means was found whereby 

 muscles which might be dilators of the buccal cavity could be dif- 

 ferentiated from dilators of the cibarium. Therefore, any dilator 

 muscles not included in the frontal complex (i. e., encircled by the 

 connectives of the frontal ganglion, hence true pharyngeal dilators) 

 are labeled as dilators of the cibarium. With very few exceptions, the 

 true pharyngeal dilators are restricted to the posterior part of the suck- 

 ing pump. It does not follow, of course, that the portion of the pump 

 derived from the pharynx is necessarily limited to this area ; it merely 

 shows the extent to which the dilators of each part have contributed to 

 the musculature of the pump. 



Mechanism. — In figure 12 A the complete musculature of the pump 

 of Dauaus nienippe is indicated. The muscles compressing the pump 

 are shown in cross-section in figure 9 A also. These muscles are 

 arranged in two groups, transverse pump muscles (tpui) and longi- 

 tudinal pump muscles (Ipm), with two layers in each group. Figure 

 9 A was drawn from a hand-cut section of the pump imbedded in 

 parafiin. Focusing through the section showed that fibers of the trans- 

 verse pump muscles passed directly into the dilating muscles, indicating 

 a possible origin of the compressor muscles from the dilators. 



At the anterior end of the pump, a group of transverse pump muscles 

 are often arranged in a distinct group, forming what Burgess (1880) 

 called the " oral valve " (fig. 8 B, OVm). Its purpose is believed to 

 be to prevent the imbibed juices from escaping when the pump is 

 emptied. This arrangement was found to be especially well developed 

 in the butterflies and in the Sphingidae. 



Comparative stnicture in lepidopterous families. — A number of un- 

 determined tineids were examined, including the common clothes 

 moth, Tincola hisellieUa. In this family the axis of the sucking pump, 

 that is, a straight line from the anterior to the posterior end of the 

 pump, is practically perpendicular to the longitudinal body axis. Such 

 a pump is illustrated in figure 10 A. A single pair of pharyngeal 



