24 lUJXOIS BIOLOGICAL MOyOGRAPIlS (24 



in the Coleoptera. In generalized insects and the more generalized 

 Coleoptera, they are situated on the lateral margin of the head. They 

 are, therefore, represented in this position on the hypothetical type. The 

 pretentorinae have been identified in every species studied except possibly 

 Calopteron (Fig. 36) and Photinus. In the latter they are represented by 

 depressions caudad of the eyes. Their position along the epicranial suture 

 varies greatly. In widely separated groups they may be primitively lo- 

 cated, as illustrated in such diverse forms as Omophron (Fig. 7), Necroph- 

 orus (Fig. 18), Scaphidium (Fig. 33), Chauliognathus (Fig. 39), Cepha- 

 loon (Fig. 46), Nacerda (Fig. 47), Alaus (Fig. 61), Phyconomus (Fig. 82), 

 and Glycobius (Fig. 123). The position of the pretentorina evidently 

 cannot possess any important significance in every instance, yet its posi- 

 tion may be characteristic sometimes. In the Scarabaeoidea it is never 

 on the dorsal surface; in the Cerambycoidea it is always on the dorsal 

 surface. In this respect, the pretentorinae and the antennariae behave 

 similarly. As a matter of fact, they are usually associated together, but 

 there are some striking exceptions. The antennariae of Macrosiagon 

 (Fig. 49) are located well caudad of the cephalic margin of the eyes, while 

 the pretentorinae are situated at the ventro-lateral margin of the head 

 (Fig. 342). The opposite condition is found in Phenolia (Fig. 79). The 

 antennariae in the vast majority of cases are caudad of the pretentorinae. 



The pretentorinae are the great landmarks of the head-capsule. On 

 their location the determination of the presence and position of the epi- 

 cranial suture is often dependent, and, consequently, the homologies of 

 large areas of the head-capsule. A case in point is that of the Rhyncho- 

 phora, in which the pretentorinae are located near the cephalic end of the 

 snout, on the dorso-lateral margin. The epicranial suture is reduced to 

 the very short cephalic ends of the epicranial arms, and though we cannot, 

 therefore, indicate with precision the cephalic limits of the vertex, its ap- 

 proximate limits can be judged, which would show the vertex to occupy 

 nearly all the dorsal and lateral aspects of the snout. 



The sclerite embraced by the epicranial arms is the front. In the 

 hypothetical type (Fig. 1) its caudal and lateral limits are the epicranial 

 arms. Its cephaHc limit is indistinguishable, since the front is fused with 

 the postclypeus. The approximate line of fusion is indicated by a dotted 

 line. There is no external indication in any head of a fronto-clypeal suture. 

 The size of the front depends upon the position and direction of the 

 epicranial arms. In those species possessing the inverted Y type of arms, 

 the front assumes considerable proportions, but where the arms have been 

 forced into a more or less straight line across the head, the invagination 

 associated with the epicranial arms includes practically the entire front. As 

 mentioned previously, the epicranial arms extend in this manner across 

 the head in a wide series of families. The front must hence assume this 



