NO. 13 LABIUM OF COLEOPTEROUS LARVAE ANDERSON 23 



In common with the labia of Chrysomeloidea (see below) there 

 are two ventral pairs of muscles. These are the ventral adductors of 

 the labium (2adlb) and the retractors of the prementum (rst). As 

 stated above, both pairs insert on the prementum, on the single sclerite. 

 The retractors of the prementum also arise on the tentorial bridge 

 lateral to the points of origin of the adductor muscles. They attach 

 on the base of the sclerite of the prementum. 



Cainptosomatidae (Cryptocephalinae) (pi. 7, B). 



The representative of this family which was used in the study has 

 the labium very similar to that of Eumolpidae (see below). The 

 labium shows a first prementum (IPrmt), and a considerably elon- 

 gated second prementum (I I Print), the elongation apparently having 

 resulted at the expense of the' postmentum (Pint), which is rather 

 short and small. 



The muscles are similar to those of the preceding family, both 

 ventral pairs originating from the tentorium. The retractors of the 

 prementum (rst) insert at a point considerably removed distally from 

 the base of the second prementum. The ventral adductors of the 

 labium (2adlh) are long- and extend to the first prementum, where 

 Ihey insert on the base of that division. 



Eumolpidae (pi. 7, E). 



The labium of Eumolpidae shows a distinct division into three 

 parts, the first prementum (IPrmt), the second prementum (IlPrmt), 

 and the postmentum (Pmt). The first prementum bears the palpi. 

 The second prementum has, near its base and closely approaching one 

 another in the midline, a pair of sclerites, each of which bears a seta. 

 There is no gula present, and the base of the postmentum connects 

 directly with the neck membrane. The two halves of the head are 

 firmly held together ventrally by the tentorial bar (Tent). 



The ventral muscles consist of two pairs, the ventral adductors of 

 the labium (2adlb), and the retractors of the prementum (rst). The 

 former originate from the tentorium and insert on the sclerotized 

 area at the base of the first prementum, near its lateral margins. The 

 retractors of the prementum (rst) likewise arise on the tentorial bar 

 but insert near the base of the second prementum on the sclerites 

 referred to in the preceding paragraph. 



Galerucidae (pi. 7, D). 



In Galcnicclla the labium consists, apparently, of but two divisions, 

 the first prementum (IPrmt) and the second prementum (IlPrmt). 

 The first prementum carries the palpi and has across its base a narrow 



