14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 95 



Dacnidae (pi. 4, D). 



The representative of this family, Tritoma unicolor Say, agrees 

 with the general type in having a three-part labium made up of the 

 first prementum {I Print), the second prementum (IlPrmt) and the 

 postmentum {Pmt). The first prementum carries the palpi and one 

 pair of setae. It is separated from the second prementum by a suture. 

 The postmentum is somewhat unusual in that its lateral margins are 

 extended anteriorly to the level of the base of the first prementum. 

 The posterior margin of the postmentum is marked by a definite 

 suture, separating it from the gula {Gu). 



The ventral adductors of the labium {2adlb) originate on the 

 posterior arms of the tentorium, close to the tentorial pits {pt). 

 They insert on the base of the first prementum. The retractors of the 

 prementum {rst) originate at or very near the tentorial pits. Their 

 point of origin so closely approaches the tentorium that it is impossible 

 to state definitely whence they arise. It is thought that they originate 

 in the angle between the tentorial arms and the postmentum. They 

 insert on the base of the second prementum. 



Anthicidae (pi. 4, E). 



Anthicus has a labium which shows the usual three divisions of 

 first prementum (IPrmt), second prementum {I I Print), and post- 

 mentum (Pint). In addition there is present a distinct gula (Gu) 

 separated from the postmentum by a definite suture. Each division 

 of the labium is set ofif from the others by sutures or grooves. 



There are two pairs of ventral muscles, the retractors of the pre- 

 mentum (rst) and the ventral adductors of the labium {2adlh). They 

 have the generalized origins and insertions. The adductor muscles 

 arise on the tentorium {Tent) and insert on the base of the first pre- 

 mentum. The retractors have their origin on the postmentum, just 

 anterior to the posterior margin of the latter, and insert on the base 

 of the second prementum. 



Byturidac (pi. 4, F). 



The labium of Byturns is like that of the preceding family in that 

 it consists of three divisions, the postmentum (Pint), the second 

 prementum (I I Print), and the first prementum (IPrmt). Behind 

 the postmentum and marked laterally by the posterior tentorial pits 

 (pt) is the gula (Gu). 



There are two pairs of ventral muscles in this species. The retrac- 

 tors of the prementum (rst) originate from the posterior margin of 

 the postmentum and insert on the base of the second prementum. 



