1930 ] Wing Venation of the Odonata and Agnatha 249 
a special group by Handlirsch, Protephemeroidea, which 
combines the characteristic venational features of the more 
primitive Dictyoneuridse and the specialized features of 
may-flies, nevertheless they still are Ephemerids, which 
preserved only the anterior branch of M of the Dictyo- 
neuridse (MA). As to the dragon-flies, Needham’s inter- 
pretation aroused doubts only in its application to the 
Zygoptera. The trachea which supplies RS in the latter 
arises from M 2 , not from R, and in general no tracheae 
which lead from R enter into the region of M. But Com- 
stock and Needham think that here also, the vein RS enters 
into the region between M 2 and M 3 , and that trachea RS 
used to arise from R and cross the media, but later “de- 
tached” itself from R and “attached” itself to M 2 . Since 
it is difficult to support the last supposition by definite 
proofs — there are none — Tillyard (15) and Rice (12) 
naturally expressed 3 doubts about the Zygoptera having RS. 
Munz, however, pointed out (9) that the conformity of the 
vain veins of Zygoptera and Anisoptera is so evident 
that it is impossible to interpret the venation of Zygoptera 
different from that of the Anisoptera, and accepted the 
old scheme of Needham. 
As I approached the study of the venation of dragon- 
flies and may-flies I thought that if the dragon-flies and 
Ephemerids were Palseoptera, 4 i. e., insects which never 
fold their wings on the back (roof -like) at rest, then not 
only the may-flies but also the dragon-flies should preserve 
the features of venation of the related Palseodictyoptera. 
If the venation of dragon-flies, according to the interpreta- 
tion of Comstock and Needham, proves to be so unusual 
that it puts them in an entirely isolated group among the 
insects, the cause of such a situation evidently lies in the 
wrong interpretation of the venation by these authors and 
the uncertainties of the ontogenetic method. It is neces- 
sary to note that at one time Redtenbach (11) offered an 
entirely different interpretation of the venation of dragon- 
flies ; attaching great importance to the alternation of con- 
3 Citing after Munz (9). 
4 Concerning the division of the Pterygota into Paleoptera and 
Neoptera, see my paper (7). 
