45] THE HEAD-CAPSULE OF COLEOPTERA—STICKSEY 45 



are no outstanding features that would warrant placing them in a separate 

 superfamily. They are negative enough in their characteristics to fit in, 

 perhaps, in a number of other superfamilies, such as the Mordelloidea, 

 Cucujoidea, and Tenebrionoidea. 



The representatives of the three families of the Byrrhoidea (Figs. 

 74-76, 222-224, 367-369, 511-513), the Dermestidae and the Byrrhidae 

 studied, Dermestes and Byrrhus, do not seem to dilTer decidedly from 

 one another, but the Nosodendronidae, represented by Nosodendron, 

 may fit in better in some other group, such as the Dryopoidea. They 

 resemble the members of this latter group in the position of the meta- 

 tentorinae and in the form of the submentum. In Nosodendron, the 

 metatentorinae are almost adjacent to the occipital foramen, with a mem- 

 branous area included between them. That part of the metatentorium 

 surrounding the periphery of the occipital foramen projects deep into 

 the head. The supratentoria are well developed. None of these charac- 

 teristics are possessed by the other two genera studied. 



The representative of the single family of this superfamily (Figs. 

 77, 225, 370, 514) studied, Rhysodes, shows distinct peculiarities in the 

 structure of its head, such as an extremely thick chitinous head-wall, a 

 fibrous condition of the cervix, an arrow-shaped head, enormously de- 

 veloped submentum, and very small mouth-parts. Its relationships are 

 not at all clear. 



The members of the Cucujoidea (Figs. 78-98, 226-246, 371-391, 

 515-535) show on the whole a short broad head-capsule, a distinct ventral 

 migration of the antennariae and pretentorinae, the degeneration of the 

 epicranial arms, and a slight migration of the metatentorinae from the 

 occipital foramen. There is some variation in the dorsal aspect. The 

 genera belonging to the Mycetophagidae, the Mycetaeidae, the Melan- 

 ophthalmidae, the Endomychidae, and perhaps those of a few other families, 

 possess dorsal surfaces that strongly resemble the dorsal surface of the 

 Mordelloidea. In Derodontus and Philothermus, a colydiid, the anten- 

 nariae and the pretentorinae are both on the dorsal aspect, located con- 

 siderably caudad. The ventral aspect of all the members of the group, 

 however, is strikingly similar. The tentorium is fairly uniform through- 

 out the group except in Tenebroides and Phalacrus, in which the preten- 

 torium has distinctly degenerated, due probably to the heavy chitiniza- 

 tion of the head-wall. In the shape of the head and the condition of the 

 metatentorinae and the gular sutures, the Cucujoidea show a similarity 

 to the Mordelloidea, and to the superfamily Tenebrionoidea. 



There are no particular characteristics of the head-capsule that would 

 separate the Tenebroidea (Figs. 99-111, 247-259, 392-104, 536-548) 

 from the typical Mordelloidea. For instance, the dorsal and ventral 

 surfaces and the endoskeleton of Arthromacra, Pseudocistela, and Penthe, 



