NO. 3 



INSECT HEA 



SNODGRASS 



99 



body of the tentorium is concave below (fig. 39 B, C, Tnt). A thin, 

 flat dorsal arm of the tentorium (fig. 39 C, DT) arises from the base 

 of the inner end of each anterior arm and extends upward and anter- 

 iorly to the wall of the cranium just before the lower angle of the 

 compound eye. The dorsal tentorial arms are attached to the hypo- 

 dermis of the head wall, but make no connection with the cuticula 

 in Dissosteira. 



THE ANTENNAE 



Each antenna consists of two larger basal segments, and of a long 

 slender flagellum broken up into about 24 small subsegments. In 



4a 



ii\ ^-tb ER 



D 



Fig. 38. — Antenna of Dissosteira Carolina and of Periplaneta. 



A, base of left antenna of Dissosteira, ventral surface. B, the _ same _ of 

 Periplaneta. C, base of right antenna and antennal muscles of Dissosteira, 

 dorsal view. D, base of right antenna, antennal muscles, anterior tentorial arm, 

 muscles arising on frons, and associated structures of Dissosteira, interior view. 



SAp, apodeme of depressor muscles of antenna; AR, antennal ridge; At, 

 anterior arm of tentorium ; c, anterior articulation of mandible ; DT, dorsal 

 arm of tentorium; ER, epistomal ridge; es, epistomal suture; ;, subantennal 

 ridge; n, pivot of antenna; OR, ocular ridge; Pdc, pedicel; Sep, scape. 



Dissosteira the antenna of the male is a little longer than that of 

 the female. Of the two basal segments, the proximal one, or scape 

 (fig. 38 A, Sep), is the larger. It is articulated to the rim of the 

 antennal socket by a small process on the lateral ventral angle of its 

 base that touches upon the margin of the socket {n). The motion of 

 the scape on the head, however, is that of a hinge joint moving in a 

 vertical plane on a transverse axis. The base of the scape is provided 



