570 METAMORPHOSIS OF INSEOTS. 
some Insects (such as the Grasshopper and the Cricket) which 
. come-forth from the egg in a form so nearly resembling that 
which they are ultimately to present, that the deficiency of 
wings is their principal difference. Such are said to undergo 
an incomplete metamorphosis; the fact being, however, not 
that these finally attain a less elevated condition than other 
Insects, but that they make a much nearer approach to it in 
that part of their embryonic state which they pass within the 
egg. In the tribes of Beetles, Butterflies, Bees, and Flies, on 
the other hand, the embryo comes-forth from the egg in the 
condition of a Worm ; and only acquires either the form or 
structure of an Insect after a complete metamorphosis, in which 
every part of its organization undergoes important modifica- 
tions. The larva, sometimes known as a “maggot,” sometimes 
as a “caterpillar” or “grub,” is in many instances completely 
destitute of legs ; and where it does possess feet by which it 
can crawl, these are not jointed members, but mere fleshy 
protuberances. The segments are all nearly equal and similar, 
both externally and internally; they are never more than 
thirteen in number, counting the head as one; and having 
been all formed in the first instance by the subdivision of the 
original yolk-mass, they undergo no subsequent augmentation 
but that of size. The voracity of the larva is its most extra- 
ordinary characteristic ; and its increase in bulk is propor- 
tional, the full-sized larva being estimated in some instances 
to weigh no less than 72,000 times as much as it did when it 
came-forth from the egg (§ 141). During this rapid inerease, its 
skin is several times thrown off; a new one being first formed 
within this, better adapted to its augmented size. Very little 
change takes place in the structure of the larva, until after 
the completion of its growth ; it then ceases to eat, and fre- 
quently forms some protection to itself, either by spinning a 
silken cocoon, or by gluing bits of stick, straw, &c. into a 
case, or it may bury itself in the ground. The last larva-skin 
hardens into a firm case around the body, which, diminishing 
in size, shrinks away from its interior. The creature, now 
known as a chrysalis or pupa, remains for some time without 
food and apparently inert ; important changes, however, are 
taking place within its body, which tend towards the forma- 
tion of the organs of the perfect insect ; and these are pro- 
duced at the expense of the mass of nutrient material that 
