256 HACHIRO YUASA 



mum size in the species having large compound eyes, as Mantis 

 (fig. 46) and Melanoplus (fig. 49). 



The lateral ocellus (lo) in Blatta (fig. 1) is in the smooth oblong 

 area located in the whitish spot in which each epicranial arm 

 terminates; the median ocellus (mo) is wanting. In other spe- 

 cies the ocelli vary in size, shape, number, and position (figs. 

 4, 5, and 10). In Diapheromera the median ocellus is wanting, 

 while in Stenopelmatus and Anisolabis all ocelli are absent. 

 When the usual number of the ocelli, three, is present, they are 

 arranged in a triangle as in Mantis. There is a sexual dimorph- 

 ism in this genus (figs. 3 and 4). 



The front (/) in Blatta is well developed and is bounded by the 

 epicranial arms, antacoriae, and frontogenal sutures on the 

 caudal and lateral aspects, respectively. The cephalic boundary 

 is an imaginary line connecting the mesal ends of the frontogenal 

 sutures or the pretentorinae. A smooth oblong spot, meso- 

 cephalad of each antacoria, is a muscle impression (mi). The 

 front varies in extent and position. Its cephalic boundary is 

 marked by the frontoclypeal suture (fcs) in all, except Orcheli- 

 mum and Stenopelmatus where the lateral boundaries are also 

 indefinite. It includes all or part of the antacoriae, frequently 

 the lateral ocelli, and the median ocellus when present. Muscle 

 impressions on the front, which have been mistaken for ocelli, 

 occur in Gryllus, Melanoplus, Tettix, and Anisolabis (fig. 12). 

 Tettix has a prominent inverted Y-shaped ridge on the front, 

 which is not connected with the frontoclypeal suture. 



Frontoclypeal sutures (fcs) are present except in Orchelimum 

 and Stenopelmatus. 



The antacoriae (an) are the circular membranous areas in 

 which the antennae are inserted. They are adjacent to and 

 mesad of the compound eyes in all the genera studied, except 

 Anisolabis where they are cephalad of them. They are located 

 on the front, except in Diapheromera and Stenopelmatus where 

 the position of the epicranial arms would indicate that they 

 belong to the vertex. 



The antennaria (ar) in Blatta is the chitinized annular sclerite 

 forming the periphery of each antacoria. Its inner margin is 



