Vol. 1.] Woodworth. — Wing Vei7is of Insects. 101 



wing, the wing of a maytiy exhibits but little that is peculiar. 

 The venation is essentially of the primitive type. There are 

 among the mayflies a number of interesting cases of reduced 

 venation. In Palingenia the arrangement of certain of the 

 independents in pairs, in the same manner as is common in 

 Odonata, is carried to a greater degree of perfection than in 

 any other insect, since it involves here the suppression of the 

 adjacent independents. In the allied Elassoneura the suppres- 

 sion of longitudinal veins is carried to the farthest extreme; 

 there only the marginal, the primary, and a single independent 

 and posterior vein remain. In Cseius and related genera the 

 reduction and finally complete suppression of the hind wing 

 have resulted in a very peculiar wing shape and venation, sug- 

 gesting somewhat Adolph's figure of a theoretical dipterous 

 venation. Among these insects we have the best examples of 

 the suppression of the cross veins. 



The homologizing of the veins in the wings of different 

 genera of Ephemeridse has been very well done by Eaton, but 

 in the comparison of the veins of the front and hind wings, 

 Redtenbacher is more successful. He has also indicated the 

 correct homologies with other insects. 



STENODICTYOPTERID.E. 



The fossil insects of this group, made known by Brongniart, 

 are of large size, and show a relatively simple venation of 

 large veins, with the membrane finel}^ and densely reticulate. 

 These characters make a very dis- 

 tinct group. The arrangement of 

 the larger veins is according to the 

 simple primitive type, and so does 

 not closelv indicate anv relation- ,„„ .- r.- < ., 



•J •' FIG. ;'..>. DiaKram ot the vena- 



Ship in particular. All the fossils 'i^" ,.of the Stenodietyopteridae, 



J^ i: omitting the very dense retieula- 



have the wings spread or broken in "o»-,. i^o^ted lines show veins 



° i sometimes wsmting. 



such a way that it is difficult to 



say whether the insects could fold the wings or not. The 

 character of the venation, as far as regards the larger veins, 

 is shown in Fig. 35. 



HOMOTHETIDiE. 



The study of fossil insects is beset with so many difficulties 

 that it is not strange that there should be room for great 

 difference in opinion. The present group, as limited by 



