120 Psyche [October 



the genitalia of the male are not sufficiently well developed to be 

 readily seen. The hypandrium, or sternal plate below the geni- 

 talia of the male, frequently bears a pair of styli on its posterior 

 margin, in these insects, and cerci are present in practically all of 

 them. The mesothoracic postscutellum is vestigial in the winged 

 forms of most of these insects (excepting the Zoraptera) and the 

 mesothoracic coxse are longer than broad in the greater part of the 

 insects constituting this superorder. The lines of descent of these 

 insects are represented in Fig. 3. 



ZORAPTERA 

 ISOPTERA 



MANTIDA 

 BLATTIDA. 

 PROTOBLATTIDA. 



Fig. 3. Lines of descent of the Panisoptera. 



Since Handlirsch maintains that the Protoblattida are inter- 

 mediate between certain of these insects and the Palfeodictyoptera, 

 the line of development of the Protoblattida has been represented 

 as the lowest in the diagram (Fig. 3), although not very much is 

 known of the structural details of the Protoblattida, to justify this. 

 The more immediate ancestors of the insects comprising this su- 

 perorder (Panisoptera) were doubtless very like the Plecoptera and 

 their allies, although the ultimate ancestral types of these insects 

 and the Plecopteroid forms as well, are doubtless to be sought 

 among the members of the Palaeodictyopteroid group. Indeed, the 

 more the Protoblattida depart from the Blattid and Mantid type, 

 the more closely do they approach the Plecopteroid type, thus 

 indicating that the latter forms resemble the immediate ancestral 

 forms from which the Panisoptera were derived. 



The Blattida and Mantida are extremely closely related and their 

 lines of descent have been represented quite close together in the 

 diagram. Taken alone, it would be rather difficult to determine 



