PHYLOGENY 

 Table I. 



101 



Carboniferous ; and the Eustheniidae (Plecoptera) from Upper 

 Permian. 



3. The Palaeodictyoptera come nearest to the theoretical 

 conception of ancestral winged insects. The Protodonata. 

 Megasecoptera and Protorthoptera were contemporaneous with 

 them in Upper Carboniferous times. Since these three orders 

 were already sharply differentiated from the Palseodictyoptera it 

 is concluded that actual ancestral insects remain undisclosed in 

 still earlier strata. 



4. The existing Ephemeroptera appear to be nearest related 

 to the Palaeodictyoptera (Dictyoneuridse), while the Orthoptera 

 and Plecoptera are clearly derivations of the Protorthoptera. 

 The Odonata apparently arose in common with the Protodonata, 

 but the ancestry of the Hemiptera and Psocoptera is obscure. 



5. The majority of the Holometabalous orders appear to have 



