22 ILLIXOIS BIOLOGICAL MONOGKAl'llS [22 



of a well marked occiput arc present in Tetracha (Fig. 2), Cicindela 

 (Fig. 3), Calosoma (Fig. 4), and Harpalus (Fig. 5). In Omophron (Fig. 

 302) the occipital suture is so short that the limits of the occiput cannot be 

 definitely determined. In those species not possessing a recognizable 

 unmodified portion of the occipital suture, the limits of the occiput can 

 only be judged accordingly. Even in generalized insects the occiput is 

 nearly always fused with the postgenae, and is so represented in the 

 hypothetical type. 



There is a great similarity in the form and location of the compound 

 eyes. The general form is oval. They are located near the middle of the 

 lateral margin of the head. Such a form and location is given in the hypo- 

 thetical type. There are a number of interesting variations in form from 

 the normal type. Dineutes (Fig. 305) and Tetraopes (Fig. 124) have four 

 complete eyes. This phenomenon is produced by a projection of a part 

 of the vertex into the eye that in time completely separates the two halves. 

 The line of closure between the projection and the opposite side is indicated 

 by a distinct line — the exoculata. The beginning of such a projection 

 is shown in Cephaloon (Fig. 46), Epicauta (Fig. 50) and many others. 

 In Pseudocistela (Fig. 99) and Osmoderma (Fig. 116) the projection ex- 

 tends more than half-way across the eye. In Throscus (Fig. 63) the 

 projection nearly separates the two halves. The eyes of Peltodytes 

 (Fig. 8), Photinus (Fig. 37) and Stenus (Fig. 22) are very large. Unusual 

 forms of the eyes are found in Hypophagus (Fig. 104), where they are very 

 long and narrow nearly meeting on the dorso-meson; in Cryptocephalus 

 (Fig. 128), where they are prominent, crescent-shaped, and extend well 

 caudad on the dorsal surface; and in Aphodius (Fig. 112), where they are 

 relatively small and square-like. The eyes of Limulodes (Fig. 324) are 

 transparent and almost invisible; those of Leptinus (Fig. 312) are com- 

 pletely wanting. 



The oculata is present only on the inside periphery of the eye as a 

 broad ring-like shelf. It is considered of little importance in this study. 

 Its general size is indicated by the dotted area within the eyes of Cicindela 

 (Fig. 298), Dineutes (Fig. 305), Passalus (Fig. 412), and a few others. 

 In forms with divided eyes the two sides of an oculata are pressed together, 

 forming an exoculata. 



The supratentorinae represent the point of attachment on the head- 

 capsule of the supratentoria. They are not thought to be primary in- 

 vaginations, and may probably represent no more than depressions. In 

 the Coleoptera the supratentorinae are not prominent, as the pretentorinae 

 and metatentorinae often are. They are situated on the dorsal surface of 

 the vertex. Their presence is not general, occurring commonly only in the 

 Staphylinoidea. Outside of this superfamily the supratentorinae are 

 found only in Phyconomus (Fig. 82) and Philothermus (Fig. 92). The 



