NORTH AMERICAN COLKOFTERA. 85 



In some other species, notably the Cetoniids and pollen-feeding forms, 

 it is entirely distinct and separate, much firmer in texture, thouj^h 

 also fringed with hair. In those cases the attachment is seen to he 

 much more to the grinder tlian to the basalis, and the connection 

 between the two is distinctly evident, wliich is not the case here. It 

 is this piece, which, when hardened and united with the other parts 

 of the mandible, forms the apical acute tooth, and justifies the term 

 "terebra." Arising from the same base as this piercer is another 

 small piece, also membraneous and fringed with hair, quite closely 

 united to the terebra. This is the prostheca of Kirby and Spence, 

 and is homologous to the lacinia of the maxilla. In some Staphyl- 

 inida) it becomes more prominent, and in some Passalidse it is modi- 

 fied into a moveable tooth above the basal or molar grinding surface. 

 There are not, so far as I know, any true appendages to the mandi- 

 bles. By this explanation it is seen that the structure of the mandible 

 is fundamentally the same as that of the labium and maxilla, and 

 that we have an equally complex organ in point of origin. Its usual 

 function, however, demands a powerful and solid structure, and the 

 sclerites are in most instances so thoroughly chitinized and so closely 

 united to the others, that practically there is only a single piece, in 

 which the homology is obscured. 



There is nothing peculiar or worthy of remark in the maxillary 

 structure. The sclerites are all well marked, and the galea is very 

 densely clothed with brownish hair on a spongy surface (see fig. 5, 

 PI. II). 



The epii)harynx is most remarkably developed in this insect, as 

 indeed it is in many others of the Lamellicorns. In dissecting out 

 the mouth parts from the macerated head after the labial and max- 

 illary structures have been removed, a cutting of all other membra- 

 neous tissue will release the mandibles and epipharynx, united as 

 shown in figures 1 and 2, of PI. II. The union is not intimate, and 

 the parts are shown in connection to give a better idea of their rela- 

 tive position and size. At PI. II, fig. 3, the epipharynx, seen from 

 below, is .separately figured to bring out its structural features more 

 in detail. It lies in the cavity of the head close beneath the upper 

 chitinous surface and moveable within ; that is, it is not attached to 

 the walls. In texture it is semi-membraneous, roughly shield shaped, 

 the lateral margins inrolled and fringed with hair, which is loosely 

 set into fovete at the edges. Inwardly it is set with rather short and 

 quite stout, moveable spines, densely massed in the centre, where a 



TR.4NS. AM. ENT. SOC. XIX. APRIL, 1892. 



