60 
DESCRIPTIVE CATALOGUE OF LARVAE. 
(' Caterpillars . Grubs, Slugs, Etc.) 
As a general rule farmers and horticulturists are not aroused to 
the necessity of counteracting their diminutive foes until they make 
their appearance in injurious numbers. It is therefore while they 
are in their most active state, while they are doing most injury, 
that they see them, and hence it is important that the characters 
by which they may distinguish them in this state should be given. 
That most insects pass through very marked changes during their 
existence, is now generally well known, and as we do not wish to 
repeat here what has been so often stated, and what will be found 
in my former reports, we will state briefly only what is necessary 
for present purposes. As a general rule, though having numerous 
exceptions, they are most injurious while they are in the larva or 
worm state, hence it is in this state they are most likely to be ob¬ 
served and to have attention called to them by the injury they do. 
But most of the systematic works on entomology describe insects 
in their perfect state: as wasps, beetles, butterflies, etc., and hence 
give but little aid to the farmer and horticulturist, who observe 
them in the larva state, and are unaware of what they are in the 
perfect state. It has been one object in my former reports, in 
speaking of injurious species, to meet this difficulty by describing 
their larval state; but the want of an arrangement to facilitate the 
determination of species in this state is yet sadly felt. To meet 
this difficulty in part, I propose to present here a kind of classifi¬ 
cation* of our most injurious species, based upon larval characters 
and habits; it is necessarily artificial, and the reader should not be 
led to suppose that those grouped together here will be found 
grouped together in the regular and natural classification, as found 
in systematic works, our only object being to assist in determining 
the species. There are many insects that undergo no marked 
changes in passing from the larval to the pupal state, and from 
the latter to the perfect state, as for example plant-lice and grass¬ 
hoppers, and all other species belonging to the orders Hemiptera 
and Orthoptera. In such cases the only changes observable are in¬ 
crease in size and the acquisition of wings. These are therefore not 
included in the present grouping, my object being to confine present 
consideration to those insects that in their larval state can be called 
worms in the general and common acceptation of that term, and 
that in passing from this state to the perfect form, become true 
chrysalides or pupae, and for a longer or shorter space of time are 
dormant. 
*This has not been carried out. 
