43] THE HEAD-CAPSULE OF COLEOPTERA—STICK.XEV 43 



Silphoidea. It has, however, developed much farther, even, than in 

 Necrophorus, being not only invaginated, but reduced to a more or less 

 rudimentary state. The first group probably evolved from the second by 

 the change in the shape of the head, due to the enormous development of 

 the compound eyes and the loss of much of the gular region, which has 

 probably fused with the cervix. Parallel with these changes, the preten- 

 toria shifted their position so that they could better support the globular 

 head, and came to assume the direction ordinarily assumed by the supra- 

 tentoria of other genera. The third group would appear to be more 

 closely related to the Mordelloidea than to this superfamily. The condi- 

 tion of the epicranial suture, the position of the antennariae, preten- 

 torinae, and metatentorinae, the degree of development of the gula and 

 tentorium, would all favor this assumption. 



The representatives of the Lymexyloidea (Figs. 43-44, 191-192, 336- 

 337, 481), two families of this group, are not very similar. Hylecoetus 

 has a head that is fairly compact, directed a little ventrad, the cervix 

 possessing a cervepisternum, and a well developed tentorium. The 

 head of Micromalthus is more compact than that of Hylecoetus, directed 

 cephalad, there is no sclerite in the cervix, and the tentorium is rudi- 

 mentary. As the superfamily stands, both could be placed in the Cu- 

 cujoidea. 



The representative of the Cupesoidea (Figs. 45, 193, 338, 482) studied 

 does not show any particular peculiarities of structure of the head that 

 would entitle it to be placed in a separate superfamily. It can be very 

 readily included with the Mordelloidea, for approximately the same reasons 

 as the Cleridae and Corynetidae. 



The genera of the Mordelloidea (Figs. 46-57, 194-205, 339-350, 483- 

 494) show considerable homogeneity. Most of them possess heads that 

 are elongate, with a generalized dorsal surface and a large postclypeus and 

 labrum, both on the same general level with the rest of the dorsal surface. 

 The epicranial suture, however, shows considerable instability, sometimes 

 showing complete arms and stem, as in Epicauta, while in others the epi- 

 cranial suture may be extremely reduced, as in ]\Iacrosiagon. If these 

 two genera are at all related, the condition of the epicranial suture can 

 hardly throw any light on the degree of relationship. On the other 

 hand, the metatentorinae are stable in position, and are located almost 

 uniformly about half-way between the occipital foramen and the sub- 

 mentum. Another characteristic feature is the fact that most of the 

 genera possess heads that are distinctly constricted at their caudal ends 

 to form a neck. The Oedemeridae, the Cephaloidae, the Pyrochroidae, 

 the PediHdae, the Anthicidae, and possibly the Cupesidae and Meloidae, 

 seem particularly closely related, through the possession of similarly shaped 

 heads, whose caudal ends are distinctly constricted, of a generalized dorsal 



