1920] Crampfon — Lines of Descent of Lower Winged Insects 119 



should have possibly been placed above that of the Plecoptera in 

 the diagram. 



Of the living forms, the Embiidina are the closest relatives of the 

 Plecoptera, the two lines of development paralleling one another 

 remarkably closely. The Plecoptera are the more primitive of the 

 two, however, and have departed as little as any known living 

 insects, from the condition typical of the ancestors of the other 

 insects of the group — and of the remainder of winged insects as 

 well. The Dermaptera are related to both Embiids and Plecop- 

 tera, and are intermediate between these insects and the Isoptera 

 in many anatomical features. The Dermaptera are also extremely 

 like the forms ancestral to the Coleoptera in regard to their max- 

 illae, antennse, terga, wing bases, elytra, cerci (compare larvae of 

 Carabidae with immature earwigs such as Dyscritina, Karschiella, 

 etc.), etc., and the members of the superorder Panplecoptera 

 exhibit many other features which must have been present in the 

 ancestors of the Coleoptera (compare head region of Harpabis and 

 Emhia, leg structures etc.). On the other hand, the Neuroptera 

 (and in some respects the Hymenoptera also) are remarkably like 

 the Coleoptera especially with regard to the structural details of 

 the larvae, so that the Coleoptera could equally well be placed in 

 the superorder Panneuroptera (to which the Neuroptera, Hymen- 

 optera, etc., belong) as in the superorder Panplecoptera, and on 

 this account the Coleoptera have been grouped with the Neurop- 

 tera only provisionally, until I am able to find the forms which will 

 enable me to determine definitely whether the closest affinities of 

 the Coleoptera are with the Dermaptera and their allies, or with 

 the Neuroptera and their allies. Anatomically, the Coleoptera are 

 clearly intermediate between the Neuroptera and Dermaptera, and 

 the ancestors of the Coleoptera were apparently intermediate be- 

 tween the Isoptera on the one hand, and the Dermaptera, with 

 their allies, on the other, although the "roots" of the Coleopteron 

 stem strike down deeply toward the Embiid and Plecopterous 

 types of insects. 



The Zoraptera, Isoptera, Mantida, Blattida, and the fossil Pro- 

 toblattida, with their immediate relatives, constitute the super- 

 order Panisoptera, whose members are characterized chiefly by the 

 markedly asymmetrical development of the genitalia of the male 

 insect, although this does not hold true of the Isoptera, in which 



\ 



