49] THE HE.iD-CAPSULE OF COLEOPTERA—STICKXEV 49 



10. What has been called the clypeal suture in such genera as Cicindela 

 and Harpalus is not even a suture, but the line of invagination of the front. 



11. The clypeus is always divided into the postclypeus and the pre- 

 clypeus. The preclypeus is with one exception always distinctly mem- 

 branous. It may be as large or larger than the labrum. 



12. There is a distinct clypealia present in the Coleoptera and in 

 widely separated groups, such as the Adephaga and the Cerambycoidea. 



13. The labrum may be indistinctly determined in both Rhynchophora 

 and other Coleoptera. It may also be quite distinct in some Rhyncho- 

 phora where it is considered to be absent. 



14. The submentum is always located distinctly cephalad of the oc- 

 cipital foramen, with a chitinized area between it and the foramen. 



15. The metatentorinae may be located on the cephalo-lateral border 

 of the occipital foramen, as in generalized insects, or they may be far 

 cephalad of this location. 



16. All that region between the occipital foramen and the submentum 

 is a part of the postgenae, produced by the fusion on the meson of the mesal 

 margins of the postgenae. 



17. The gular sutures result from the cephalic migration of the meta- 

 tentorinae. 



18. The gula is that area included between the gular sutures, and is, 

 therefore, derived from the postgenae. The majority of the Coleoptera 

 possess a gula that extends no more than half the distance between the 

 occipital foramen and the submentum. 



19. The tentorium of the Coleoptera is typically quite similar in form 

 and development to that of generalized insects. Frequent modifications 

 are loss of chitinization, loss of corpotentorium and laminatentorium. 

 Occasionally the pretentorium may be rudimentary. The functions of 

 the absent parts are assumed by other parts of the tentorium, or by the 

 pharynx, or the head may be so compact and chitinized that a tentorium 

 is no longer needed. 



20. The cephalic migration of the submentum, and the subsequent 

 formation of an indistinguishable area between it and the occipital fora- 

 men is due either to the migration caudad of the occipital foramen or to the 

 cephalic pull on the mouth-parts or to both. The cephalic migration of 

 the metatentoria and, therefore, the metatentorinae, with consequent pro- 

 duction of the gula, is probably due to the cephalic pull on the tentorium to 

 furnish a firmer support for the muscles and tendons of the mouth-parts. 



