INTRODUCTION. 
ID 
which certain generations are viviparous without any 
sexual process.* It has been said that insects as a rule 
are oviparous though they may be viviparous. Some¬ 
times the larva is so far developed within the maternal 
oviduct, as to be almost ready to enter on its second or 
pupal existence on its appearance into the world. 
Insects, as a rule, in their development from the egg, 
undergo, as is well known, a series of changes called 
metamorphosis ; this is sometimes very complete or in¬ 
complete, and sometimes there is no change of form. 
As instances of complete metamorphosis I may mention 
butterflies, moths, and beetles, which go through 
three distinct stages called the larva , pupa, and imago , 
or perfect state. In the first stage the insect is like a 
grub, either provided with legs or destitute of those 
organs; in common language we call them caterpillars, 
maggots, or grubs; during this period eating is the 
order of the day, and this they do generally very vora¬ 
ciously, and in many cases most injuriously to the 
cultivated products of the soil. After repeatedly 
changing the skin to allow of the creature’s growth, for 
the skin does not grow with the body, it assumes the 
pupa , or as it is usually called amongst butterflies and 
moths, the chrysalis stage. Here is perfect quiescence, 
the creature neither moves nor eats; there is death-like 
repose for a period, more or less long, according to the 
species. But though externally no change is visible, a 
wonderful drama is being acted “ behind the scenes,” 
and in due time that which entered the pupa state a 
grovelling grub emerges from it a beautiful winged 
* 
See Rolleston’s “ Forms of Animal Life.” cxii. 
