98 ENTOMOLOGICAL NEWS [xxxii, '21 



forms in support of the view that the Homoptera and Thysan- 

 optera were descended from ancestors resembling the Psocida, 

 and that the common ancestors of all of these forms were 

 closely allied to the Zoraptera, which in turn lead back to 

 ancestors resembling the Embiida (with their allies the Ple- 

 coptera) and ultimately to forms not unlike the fossil Haden- 

 tomoida, Haplopteroida, and other related insects derived from 

 the Palaeodictyoptera. 



Before taking up the subject of the evolution of the Zorap- 

 teron type of wing, I would call attention to the fact that 

 there are two ancient tendencies traceable in the development 

 of the wing veins, the one tending toward an oUgoncnrous type 

 of wing with comparatively few cross veins and few branches 

 of the main longitudinal veins, while the other tends toward 

 a polyneurous type of venation with more numerous cross 

 veins, more branches of the longitudinal veins and other fea- 

 tures. These two tendencies apparently originated at an early 

 date possibly at the very beginning of the evolution of winged 

 insects and continuing even into the more highly modified 

 orders, they affect the venation of these forms in varying 

 degrees. A great development (in the hind wing) of what 

 Handlirsch, 1906, terms the anal fan, or the feeble develop- 

 ment of the anal region of the wing, the presence of numerous 

 cross veins in the costal region of the wing, or the tendency 

 to develop but few of the cross veins in this region, and the 

 branching, or the non-branching of the subcosta, are some of 

 the features which apparently developed at an early stage of 

 the evolution of winged insects possibly manifesting them- 

 selves to some extent at the very beginning of the develop- 

 ment of the Pterygota and it is necessary to trace such of 

 these tendencies as are carried over into the insects related 

 to the Zoraptera, from their .earliest inception, if the lines of 

 development of these forum are to be represented with any 

 degree of cotrpletene iii a d'a :ram of the phylogonetic tree of 

 Pterygotan insects. For the purpose of the present paper, 

 however, it will be sufficient to begin the evolutionary series 

 with those forms arising directly from the Palaeodictyopteron 

 stock, such as the Hadentomoida, Haplopteroida, etc.. \vhich 

 gave rise to the types ancestral to the Zoraptera and their 

 allies. 



