138 ENTOMOLOGICAL NEWS [xxxii, '21 



the Coleopterous types in some respects. Taking their anatomy 

 as a whole, I would therefore maintain that the closest affinities 

 of the Hymenoptera are with the Neuropteroid insects (Mecop- 

 tera, Neuroptera, etc.), and that the lines of development of 

 the Hymenoptera and other Neuropteroids quickly merge with 

 those of the Psocoid insects (i. e., the Homoptera, Thysanop- 

 tera, etc.) as we trace them back to a common ancestry 

 anatomically intermediate between the Zoraptera (with the 

 Isoptera) and the Coleoptera (with the Dermaptera). 



The Zoraptera in turn lead back to forms closely resembling 

 the Embiida and Plecoptera, as is also true of the Coleoptera 

 and Dermaptera. In fact, the resemblance between the Coleop- 

 tera and Embiida is quite marked in the character of the 

 mouthparts, metathoracic coxae and other features ; and the 

 tendency for the fore wing of the Embiida to preserve the 

 longitudinal veins in the form of long nervures extending 

 almost parallel to each other down the wing (e. g., as shown 

 in Fig. 7 ) is certainly very suggestive of the condition oc- 

 curring in the fore wings of Coleoptera. The venation, there- 

 fore, would admit of a close relationship between the Coleop- 

 tera* and the Embiida which is indicated by the mouthparts 

 and other structures, and it is evident that the lines of develop- 

 ment of all of the forms mentioned above quickly merge as 

 we trace them back to ancestors resembling the Embiida and 

 Plecoptera, which in turn, are connected with the Palaeodicty- 

 optera by such forms as the Hadentomoida. Haplopteroida, 

 etc., if we may judge by the nature of their wing veins. 



The appended diagram, in which the principal lines of 

 descent have been linked together "in twos" (merely for the 

 sake of convenience) will serve to illustrate the derivation 

 and interrelationships of the orders of insects mentioned above. 

 Since several lines of descent may arise at the same "point" 

 on the ancestral tree (i. e., their common ancestors were 

 enough alike to be grouped in a single order) these lines of 

 descent should be considered as though drawn in a figure of 



* The ancestors of the Coleoptera were anatomically intermediate 

 between the Isoptera on the one side, and the Dermaptera on the other, 

 and all three of these lines of descent lead back to ancestral types re- 

 sembling the Embiida (with the Plecoptera) on the one side, and the 

 Protoblattida 011 the other. 



