XXXVI INTRODUCTION. 
their metamorphosis at all resembling the pupa, or 
chrysalis state in insects.* 
All insects pass through four states,—namely, 
that of the egg ; the larva, or caterpillar ; the pupa, 
or chrysalis ; and the imago, or perfect insect. So 
called by Linneus, because the creature has thrown 
off its mask, and has become a perfect image of its 
species. These different forms I shall treat in suc- 
cession. The egg state will apply to the whole 
order; but I shall only enter into a general account 
of the physiology of the larvee condition, as applied 
to the three genera, Butterflies, Sphinges, and Moths, 
and give a detailed account, in the first instance, 
of Butterflies ; reserving the most singular facts 
which are connected with the history of Moths, to 
precede the description of the animals of that genus. 
When we alter the soil of a country by agricul- 
tural operations, plants will follow, of their own 
accord, the progress of man’s improvement ; and 
wherever plants are introduced, animals are certain 
to find their way thither. It would be difficult to 
give a satisfactory account how this takes place. 
Let brassicas be introduced into the most remote 
“ Sce Kinny and Spence, Intr. vy. pl. i. p. 81. 
