20 
INTRODUCTION. 
insect, gorgeous in colouring, graceful in form, and 
endued with high powers of rapid flight. The insect is 
now in its imago or perfect state; with the exuviation 
of the pupa-integument it has cast off* all the vestiges 
of the organs characteristic of the larva stage, and 
assumed true legs, wings, compound eyes, antennae, a 
more perfect nervous system, and most wondrous, 
perhaps of all, the biting jaws of the injurious cater¬ 
pillar have been metamorphosed into the delicate spiral 
“ tongue” of the nectar-sipping butterfly! Not, how¬ 
ever, immediately on emerging from the pupa-case is 
the perfect insect ready to beat the air with its wings 
and to fly where it listeth, for at first the wings are “Soft 
and crumpled, hanging loosely at the sides of the body, 
but after exposure for some little time to the air, and 
when the tracheal system has by inspiration and expira¬ 
tion become fitted for aerial flight, the insect sails away, 
and its wings, now possessing the necessary stiffness for 
organs of impulsion in the air, are henceforth the crea¬ 
ture’s chief instruments as means of locomotion. In 
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cases of such a complete metamorphosis as these, there 
is a wonderful dissimilarity between the larva and the 
imago, and insects undergoing the three distinct changes 
of larva, pupa and imago, are called “Holometabolous.”* 
But though complete metamorphosis obtains in the 
majority of the Insect class, there are many kinds in 
which the changes are partial and incomplete. In these 
cases of semi-metamorphosis the larva bears some re¬ 
semblance, more or less exact to the perfect insect, the 
* i.e ., undergoing complete change, from u\oq “ whole,” and 
HirafioXi) “change.” 
