292 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
general rule can be laid down as to the relative proportions of the epi- 
cranium and of tlie clypeus, or of the gular region. 
On this account I had at one time decided to split the group into two, 
and to restrict Erichson’s Pscu doneuroptera to the Platyptera, 1 * 0 and to 
adopt Latreille’s term Subulicornia for the Odouata and Ephemerina 
( SubuUcornes of Latreille). It may, however, be best, for the sake of 
clearness, to retain Erichson’s order Pseudoneuroptera as he indicated 
it, and to dismember it into what may be regarded, provisionally at 
least, as three suborders : 
1. Platyptera (Termitidaj, Embidae, Psocidm, and Perlid3e:=Corroden- 
tia and Ortlioptera ampliibiotica in part). 
2. Odonata (Libellulidse). 
3. Eplicmerina (Ephemeridse). 
It is comparatively easy to give well grounded differential characters 
for these three suborders. They are so distinct that they may perhaps 
hereafter be regarded as entitled to the rank of orders, or the Pseudo- 
neuroptera may be dismembered into the Pseudoneuroptera and Subuli- 
coruia (Odonata and Ephemerina). 
1. Platyptera. — The body is flattened; the head horizontal. The pro- 
notum is large, broad, and square. The meso- and metauotum are re- 
markable on account of the imperfect differentiation of the scutum and 
scutellum ; the latter is indefinite in outline, but very large. The flanks 
(pleurites) are, when long, oblique, or are short. The sternites are usu- 
ally very large and broad. There are often eleven uromeres. 
2. Odonata . — While the Odonata and Ephemerina are somewhat alike 
as regards the form and venation of the fore wings, in their mouth -parts 
and thorax they are entirely unlike. The Odonata are remarkable for 
the great dorsal (tergal) development of the mesepisterna and the enor- 
mous development of the meso- and metapleurites in general, while 
the notum of the meso- and metathorax, though of the same type as the 
Orthoptera, is minute in size. The prothorax is very small, both dor- 
sally 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 remarkably small compared with 
that of the Orthoptera, and forbids their union with this order, as was 
done by Gerstacker and other German entomologists. The head of the 
Odonata is remarkable for the enormous size of the eyes and the con- 
sequent great reduction in size of the epicranimn, as compared with 
the large epicraniuin of the Orthoptera. The mouth-parts are like 
those of the Orthoptera, except that the second maxillae form a re- 
,40 Thi8 name n\arvs, flat, nrtpov, wing, in allusion to the wings which in the minority (the PsocidsB 
folding their wings rather roof-like) fold their wings flat on the back. The Ibon^raof Iimll6 comprise 
the Tennitidic alone. 
