102 Annals Entomological Society of America [Vol. V, 
In some generalized wing-pads a weak branch springs from 
the cubito-anal loop and extends inward toward the body, 
nearly parallel with the main stem. (b, in Fig. 5,C). These 
structures have prompted the suggestion that the weak 
trachea (b, in Fig. 5, C) may be the remnant of the trachea 
which connects the trachea of the wing with the ventral body 
trachea in other orders (b, in Fig. 5, A). 
Fossil May-flies. 
On account of the difficulty in studying fossil wings only a 
very brief consideration has been given to them. A few figures 
of fossil wings believed to be those of May-flies have been 
copied. (PI. IX, Figs. 62, 63, 64, 65, 66, 67). The homologies 
here determined have been applied to these wings. All but the 
last figure are taken from ‘‘Types of Permian Insects’ by 
E. H. Sellards!. In these May-flies the fore and hind wings are 
nearly equal in size, as they are in damsel-flies. The parallel 
veins of the front part of the wing and the main branches of 
media are identical with those of modern May-flies. The last 
figure (Betis anomala)? represents a recent fossil in which the 
hind wings show the reduction which is the present character- 
istic of May-flies. 
Hind Wings. 
The hind-wings of May-flies are greatly reduced in size. 
In Cenis they are entirely lacking. In consequence of this 
reduction there are important differences in the front and hind 
wings. By reason of it also the venation is so reduced as to be 
of far less value in practical use. 
The wing-pads of Chirotonetes show the most generalized 
tracheation of any which have been studied. In these the bases 
of the tracheal trunks are similar to those of the front wing 
(Pl. VIII, Fig. 43). The tracheae however show these differ- 
ences. The M, trachea always extends to the margin of the 
wing-pad. There is no trace of either the Rs? or the Ist acces- 
sory trachea. These veins, however, are present and occupy 
positions identical with the corresponding veins of the front-wing 
1E. H. Sellards. Types of Permian Insects. Amer. Jour. of Science, Vol. 
XXIII, May, 1907. pp. 345-355. 
2G. C. Berendt. Die im Berstein befindlichen Organischen Rests der Vorwelt. 
1856. Zweiter Band. Abt. II. Neuropteren (Pictet Baraban & Hagen). Tab. VI, 
Fig. 1. 
