354 Annals Entomological Society of America [Vol. IX, 



The wings in these groups are misleading phylogenetically, 

 since the venation seemingly is very simple in some instances, 

 and actually so in others. Of course, a sub-aquatic life must 

 profoundly modify the organs of flight if they are unused, so in 

 Plea the specialization reaches such a degree that the second 

 pair of wings is absent and the first pair is completely coriaceous 

 and hardened and soldered together, which, in passing, is also 

 the case in the genera Nerthra of North America and Peltopteriis 

 of Africa, in the Gelastocoridce, which are forms living on the 

 banks of streams and bodies of water; and in the Aphelocheirince 

 of the Old World, certain dimorphic species exhibit wingless 

 forms. In Ranatra the cross veins of the second pair of wings 

 are reduced to mere spurs arising from the longitudinal veins, 

 and in the first pair are entirely absent. In A?iisops and 

 Buenoa, Etiithares and Nychia, the entire hemelytra (also 

 called tegmina) are hyaline and with nothing but a few nearly 

 obsolete longitudinal veins, and in the last named, the second 

 pair of wings is absent. All the Belostomatidce are strong 

 fliers, and here, as may be imagined, the wings are large and 

 powerful, the venation of the upper and lower pairs complete, 

 except that in some forms, the membrane of the tegmina is 

 nearly obsolete. The Naiicoridce also have unspecialized wings 

 and the Corixidce as well, in the majority of cases. To anyone 

 at all familiar with these groups at first hand, the absurdity 

 of calling them primitive is self-evident. From what has been 

 said, it can readily be seen that the wings in the aquatic forms 

 are unreliable and misleading as criteria of position in the 

 phylogenetic scale. Where they have continued to be of use, 

 the wings persist in a fairly non-complex form ; where disuse has 

 ruled, they have been modified and even have become obsolete 

 to the extent of disappearing. 



The most profound changes, as might be supposed, have 

 taken place in the respiratory apparatus, which has become 

 adapted in the most remarkable ways to aquatic life ; and in the 

 legs which have been transformed to cope with the medium in 

 which the insects move. There are three main forms of 

 respiratory apparatus among the water- dwellers, which may 

 be called the dorsal reservoir and pile, the anal tube, and the 

 abdominal channel types. The tracheal systems as such are 

 practically identical in all three forms of air supply. The 

 Corixida, Belostomatidce and Naucoridce have the dorsal reser- 



