232 Prof. J. C. Schiódte on the Morphology 
and which in reality expresses itself with all desirable sharp- 
ness in a certain feature of external structure. In order to 
cause the two contrary movements, viz. the pressing backwards 
of the head and the rostrum and the pressing forwards of the 
body, to cooperate under the most favourable conditions by 
the diminution of the distance between their starting-points, 
the forehead is bent so far in under the animal that a struggle 
for space, so to say, arises between the head and the fore legs, 
which only can be solved by a compromise, namely thereby, 
that the coxe of the fore legs to a certain extent are accommo- 
dated in the head, in excavations of the cheeks, which con- 
sequently, though it sounds absurd, really take part in the 
formation of the articular socket of the first pair of coxe. By 
this arrangement it becomes, of course, impossible for Homo- 
ptera to turn their head during perforation or suction; they 
are unable to do more than to raise or depress it a little.. In 
Heteroptera no such thing takes place, however broad and flat 
their head may appear: the cheeks only reach to the proster- 
num, but never so far as the front legs, and the head therefore 
retains its capability of turning on the protracted cervical 
process. These facts, then, lead to the following diagnosis of 
the two suborders :— 
Homoptera. First per of coxz articulate with the cheeks. 
Heuer Cheeks and first pair of coxa do not touch 
ach other. 
III. 
_All Homoptera are Pagiopoda and phytophagous ; they ex- 
hibit a great variety of forms, which, however, all range 
