12 
INTRODUCTION 
not academically accurate, but sufficiently so for practical purposes. As 
knowledge grows, as groups are revised, new views are expressed, new 
systems adopted. This would matter little if there were, for instance, 
agreement as to one unit, say the family, if it could be decided that 
Coleoptera. for instance, are a homogeneous group of say 80 families ; 
unfortunately this is impossible at present. Actually, insects are prima¬ 
rily divided or have been divided into primary divisions called orders. 
Thus Coleoptera are a distinct enough order ; when we go below this, we 
should have a definite number of sub-orders, each containing a 
definite number of families ; the sub-family is the next division 
containing a number of genera. Unfortunately superfamilies, legions, 
cohorts, tribes, etc., have been used, and it is rare to find all authorities 
on an order or sub-order using the same classification. 
In this volume, we propose to follow the Fauna of India, in using 
the terms order, sub-order, family, sub-family, division, genus, species, 
but as classification is not our main object, we can largely simplify the 
system actually used in the Fauna. 
Entomologists have adopted the family as the unit of classification 
trying to group insects first into divisions which must have had a 
common ancestor ; on this basis we get nearly 300 families, each of 
which represents a fairly homogeneous assemblage, derived from one 
branch of the tree ; the difficulty is greater when we try to group these 
families to find the main limbs of our tree or to find how many 
separate limbs we should have, derived each from some lower form of 
life ; for instance, Lepidoptera area very homogeneous order, the families 
derived from one branch ; Orthoptera on the other hand are by no 
means uniform, and so far as can be seen, the order instead of coming 
from one branch may really come from three ; none the less, in the 
absence of sufficient data to find really how many branches there are, 
the order Orthoptera as here adopted is a very convenient one. Our 
nine orders are constituted then with a regard both to truth and con¬ 
venience and a student should think in terms of families, grouping these 
families into aggregates which we may call sub-orders and orders. 
In practice we have to utilise a conventional system that embodies 
as much truth as possible and which is reasonable for working purposes. 
Of the nine orders we adopt here, seven are generally accepted by 
entomologists, but there is great divergence of views over the Neurop - 
