346 ENTOMOLOGICAL NEWS [Oct., '15 



and the Hemiptera-Homoptera, and it is with the Neuroptera 

 and Homoptera that the Psocidae show the closest affinities. 

 It is quite true that the ancestral Neuroptera very closely ap- 

 proach the ancestral Plecoptera, and in this way the Psocidae 

 would be related to the Plecoptera and Isoptera, but the rela- 

 tionship is a rather indirect one, and, as has been stated, the 

 affinities of the Psocidae are rather with the Homoptera and 

 Neuroptera, than with the Plecoptera and Isoptera. 



The complicated inter-relations of the various orders of in- 

 sects makes it extremely difficult to arrange them in clearly de- 

 fined groups. There are, however, at least two clearly de- 

 fined "nuclei," or centers, about which the majority of pterygo- 

 tan insects group themselves ; further investigation will doubt- 

 less disclose other such centers. The two centers in question 

 are the Neuroptera and the Plecoptera, and the ancestors of 

 both of these groups were, in all probability, derived from 

 forebears similar enough to be grouped into a single family. 



The insects which group themselves about the "Neuropteron- 

 center" constitute a supersection which may be referred to as 

 the Neuropteradelphia (or "Neuropteron-brotherhood"), and 

 all are the descendants of very similar ancestors — i. e., their 

 ancestors would have been grouped into a single family. Here 

 belong the following orders : Neuroptera, Trichoptera, Lepi- 

 doptera, Mecoptera (Panorpidae), Diptera, Siphonaptera, 

 Homoptera, Heteroptera. Clinoptera (Psocidae), and others. 



The insects which group themselves about the "Plecopteron- 

 center" constitute a second supersection which may be referred 

 to as the Plecopteradelphia (or "Plecopteron-brotherhood"), 

 and all are the descendants of very similar ancestors. Here 

 belong the following orders : Plecoptera, Platyptera (restrict- 

 ed to the Embiid-like insects), Dermaptera, Notoptera (Gryl- 

 loblattid-like forms), Zoraptera, Isoptera, Cheleutoptera (Phas- 

 mid-like forms), Phylloptera (Phyllium-\ike forms), Diph- 

 theroptera (grasshopper-like forms), Orthoptera ("Locus- 

 tidae" and Gryllidae), and others. 



The orders Palaeoptera (Blattid-like forms) and Dictyop- 

 tera (restricted to the Mantid-like forms) are very closely 



