22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



The ventral labial muscles again consist of two pairs. The ventral 

 adductors of the labium (2adlb) originate from the tentorial bar 

 (Tent) and insert on separate sclerites in. the small first prementum. 

 The retractors of the prementum (rst) arise from the postmentum 

 and insert beyond the middle of the elongate second prementum. 



Meloidae (pi. 7, C). 



The first prementum (I Print) and the second prementum (IlPrmt) 

 are clearly set off from one another and from the remainder of the 

 labium. The postmentum and gula (Gu + Pmt) form a continuously 

 sclerotized area and neither one is to be easily differentiated from 

 the other. Since the bases of the tentorial arms have become greatly 

 elongated into low ridges the tentorial pits are not clearly marked 

 and can not be used to separate the postmentum from the gula. 



Corresponding to the division of the prementum there are two ven- 

 tral pairs of muscles. The retractors of the prementum (rst) arise 

 on the postmental area and insert on the base of the second pre- 

 mentum. The ventral adductors of the labium {2adlb) arise on the 

 ridgelike tentorial arms and insert on the base of the first prementum. 



Cerambycidae (pi. 7, A). 



The labium of Orthosojna shows the divisions which are typical 

 of adult Coleoptera and of Orthoptera (pi. i, B, C) : a distal pre- 

 mentum (pi. 7, A, Prmt), and a postmentum {Pmt) subdivided into 

 a mentum {Mt) and a submentum (Smt). 



The muscles of the labium consist of one ventral and one dorsal 

 pair, the ventral adductors of the labium {2adlb) and the dorsal ad- 

 ductors of the labium (ladlb) respectively. They both have their 

 origin on an extension from the tentorial bridge (Tent). The ventral 

 adductors insert on the base of the prementum near the ventral mid- 

 line. The dorsal adductors attach dorsally near the lateral margins of 

 the base of the prementum. 



Bruchidae (pi. 7, F), 



The labium of Spcrnwphagus shows a remarkable departure from 

 the labia of coleopterous larvae in general in that the labial palpi are 

 entirely lacking. The prementum (Prmt) simply ends bluntly. The 

 first and second prementa are completely united, although the united 

 region has two pairs of ventral muscles. The postmentum (Pmt) 

 contains a sclerite which has a shape much resembling that of a 

 new moon. The postmentum is considerably broader than the pre- 

 mentum and extends laterally nearly to the median margin of the 

 cardo (Cd). 



