1974] 
Kukalova-Peck — Pteralia 
421 
occurred later in evolution. This conclusion is supported by the 
morphology of primitive Permian mayfly families, the Protereismati- 
dae and the Misthodotidae. In both, the stems of main veins were 
strong, reaching the wing base, and the anal brace was less pro- 
nounced than in extant mayflies (fig. 7). It should be noted that the 
adult life span in Permian Ephemeroptera was probably longer than 
in Recent species; the presence of large and apparently fully func- 
tional mouthparts in the adult Permian Misthodotidae (Tschernova, 
1965) is very suggestive that these particular mayflies, at least, were 
active feeders. Flight was presumably important in obtaining food, 
as well as in courtship activities. 
According to Brodskyi (1970), the second axillary sclerite in 
Recent Ephemeroptera is firmly fused with the axillary plate, al- 
though this opinion is not shared by some other specialists; the sche- 
matic figure of the axillary region in extant mayflies (Leptophle- 
biidae) in the interpretation of Tsui and Peters (1972) is shown in 
figure 5. In the fossil material described, no remnants of the axillary 
region have been mentioned so far. 
Fig. 5. Axillary region of fore wing of ephemeropteron, Aprionyx 
tricuspidatus (Leptophlebiidae, adult male). After Tsui and Peters, 1972. 
AxPl — axillary plate; Ax 1, 2, 3 — axillary sclerites; HP — humeral 
plate; T — tegula. Recent. 
Diaphanopterodea 
The Diaphanopterodea have mouthparts, genitalia and wing vena- 
tion pattern very similar to those of Palaeodictyoptera, from the 
primitive forms of which they were probably derived (Carpenter, 
