4 
MEMBRA ClDAE. 
The position of the Membracidae may be briefly shown by the following table : 
< 
£H 
O 
o 
Pn 
P3 
w 
n 
a 
O 
Section. 
<jj 
W 
f Monomera 
s 
0) 
+= 
O-i J 
o ' 
a 
o 
K 
Dimera 
Trim era 
Families. Sub-Families. 
Scutelleridae. 
Cimicidau 
Ac. Ac. 
Coccida*. 
Aphidae. 
Cicadidae. 
Ledridse. 
Membracidae 
Fulgoridae. 
Cei'copidae. 
Jassida?. 
/Membracinae. 
Darninae. 
Tragopinae. 
Smiliinae. 
Hoplophorinae. 
Centrotinae. 
t4£thalioninas. 
With reference to the classification of a group of animals, an ordinary observer 
might at first think that the task would he easiest where there was found to be the 
greatest variety of form. This does not necessarily follow. Diversity may proceed 
from a departure from a few marked types, perhaps originally constant; or, on the 
other hand, from the types themselves as numerous, and yet liable to modification. 
The great variety of form in the Membracidae seems to be a hindrance rather 
than an assistance to a natural classification, when it is found that characters, 
thought good as generic in some families of insects, are sometimes found not 
constant even in the sexes of other families. Facts of metamorphoses and life- 
history here are great and almost indispensable desiderata for a natural arrangement. 
William Macleay well observed that any Entomological system which does not 
concern itself with the phenomena of metamorphoses, in fact, ignores the existence 
of half the insect world. 
The study of adult forms alone, when the wants of the previous life which 
may have been so essentially different from those afterwards developed are ignored, 
must be in many ways deficient. Yet this deficiency must be tolerated if the life- 
histories of the insects are obscure. A whole history is possible only when materials 
are abundant for the study. 
Our classifications are, for the most part, arbitrary. We may attempt such 
either by a process of eliminating parts of structure which we may consider of 
secondary importance, and thus work for the discovery of a type ; or we may infer 
