934 On the Genealogy of the Insects. |September, 
rites are also very oblique and the femora are flattened and ovate 
in form, as in Blatta. In the abdomen, as regards the form of the 
tergites, as well as the urosternites and pleurites, besides the form 
of the end of the abdomen and of the cercopoda, the Termitide 
closely approach the Blattarie. The degree of metamorphosis 
is also the same. 
On the other hand, the close relationship of the Termitide to 
the Embidz, as well as to the Psocidz and also the Perlide, and 
the close resemblance of the Perlid larvae to those of Odonata 
and Ephemerina, forbid our removing the Platyptera from the 
Pseudoneuroptera. 
We conclude, then, that the Ephemerina, Odonata, Platyptera, 
as well as Orthoptera and Dermatoptera have had a common ori- 
gin from some Thysanuran stock. It is possible that these five 
groups are nearly equivalent and should take the rank of orders, 
but the classification we have given in the tabular view on p. 932 
may better express their relations. 
The Odonata and Ephemerina are, as regards the wings and 
metamorphosis, a good deal alike. The Ephemerina, while hav- 
ing a highly concentrated thorax, are, as regards the mouth-parts 
and hind wings, degradational forms, the result of probable de- 
generation from a primitive, lost form. From what group the 3 
Ephemerina may have originated it seems to us impossible to a 
conjecture. 
V. Hemiptera—The only clew to the origin of this well cir- 
cumscribed order is the fact that in. the Physapoda (Thrips) and ee 
the Mallophaga the mandibles are free and adapted for biting: : e 
This would indicate that the entire group was derived from ances- - 
tors allied possibly to the Phyloptera. The Mallophaga are ae 3 
different authors referred to the Orthoptera and Neuroptera, but A 
the development of the bird-lice as worked out by Melnikow 
fully proves that in the form of the egg, the mode of dn . 
ment and general form of the embryo, the Parasita and Mal A < 
phaga travel along the same developmental path until just pe —— 
hatching, when in Mallophaga the jaws remain free, while ee A 
Parasita they become further modified and form a sucking t 
There is a possibility that the Hemiptera may have d A 
from insects remotely allied to the Pseudoneuroptera ; pe 
forms resembling the Psocidæ; at least this family, the wing! a 
forms of which superficially resemble the Mallophag a 
