1883. } of Orthoptera and Neuroptera, 827 
Odonata are remarkable for the great dorsal (tergal) development 
of the mesepisterna and the enormous development of the meso- 
and metapleurites in general, while the notum of meso- and meta- 
thorax, though of the same type as the Orthoptera, is minute 
in size, The prothorax is very small, both dorsally and on the 
sides forming a collar. 
The wings are as markedly net-veined as in the Orthoptera, 
though the hinder pair are not folded longitudinally as in that 
order. The Odonata literally live on the wing, and thus the 
shape of the sclerites of the notum of the wing-bearing segments 
approaches that of the Orthoptera, although the prothorax is re- 
markably small compared with that of the Orthoptera, and for- 
bids their union with this order, as was done by Gerstacker and 
other German entomologists. The head of the Odonata is re- 
markable for the enornious size of the eyes and the consequent 
great reduction in size of the epicranium as compared with the 
large epicranium of the Orthoptera. The mouth-parts are like 
those of the Orthoptera except that the second maxilla form a 
remarkable, mask-like labium. The abdomen is very long, slen- 
der and cylindrical; there are eleven uromeres, the eleventh be- 
ing well represented, while the cercopoda are not jointed but in 
the form of claspers. 
3. Ephemerina—In the small epicranium and the large male 
eyes the Ephemerina resemble the Odonata, though the rudi- 
mentary mouth-parts are in plan entirely unlike them. So also 
the prothorax is small and annular, but the subspherical, con- 
centrated thorax is remarkable for the large mesothorax and the 
small metathorax. Hence, the hind wings are small and some- 
times obsolete. The long, slender abdomen has ten uromeres, 
and bears, besides the two long filamental multiarticulate cerco- 
poda, a third median one. 
The larve of the lower Odonata and of the Ephemeride 
closely approach in form those of the Perlidz, showing that the 
three suborders here mentioned probably had a common ances- 
try, which can be theoretically traced to a form not remote from 
Campodea. By reason of the general resemblance of the larval 
forms of these three suborders it would be inadvisable to separate 
the Odonata and Ephemerina from the Platyptera, although when 
we consider the adult forms alone, there would appear to be some 
§founds for such a division. 
VOL. XViI.—nNo. VI. 56 
