Development and Metamorphosis 
45 
larva is like that of a worm, to accomplish wriggling, crawling, worm-like 
locomotion; in the adult it is very different, particularly in head and thorax; 
the alimentary canal is usually adapted in the larva for manipulating and 
digesting solid foods; in the adult, usually (except with the beetles and 
a few other groups), for liquid food; there may be large silk-glands in the 
larva, which are rarely present in the 
adult; the respiratory system of the larvae 
of some flies and Neuroptera is adapted 
for breathing under water; this is only 
rarely true of the adults. The heart 
and the nervous system show lesser dif¬ 
ferences, but even here there is no iden¬ 
tity : the ventral nerve chain of the larvae 
may contain twice as many distinct gan¬ 
glia as in the adult. 
The larva lives its particular kind of 
life: it grows and moults several times; 
but externally it shows at no time any 
more likeness to the adult than it did at 
hatching. But after its last moult it ap¬ 
pears suddenly in the guise of a partially 
formed adult in (usually) quiescent mummy-like form, with the antennae, 
legs, and wings of the adult folded compactly on the under side of the 
body, and the only sign of life a feeble bending of the hind-body in re¬ 
sponse to the' stimulus of a touch. This is the insect of complete meta¬ 
morphosis in its characteristic second stage (or third if the egg stage 
is called first), the pupal stage. The 
mummy is called pupa or chrysalid. As 
the insect cannot, in this stage, fight or 
run away from its enemies, its defence 
lies in the instinctive care with which the 
larva, just before pupation, has spun a 
protecting silken cocoon about itself, or 
has burrowed below the surface of the 
ground, or has concealed itself in crack 
or crevice. Or the defence may lie in the fine harmonizing of the color and 
pattern of the naked exposed chrysalid with the bark or twig on which it 
rests; it may be visible but indistinguishable. The insect as pupa takes 
no food; but the insect as larva has provided for this. By its greed and 
overeating it has laid up a reserve or food-store in the body which is drawn 
on during the pupal stage and carries the insect through these days or weeks 
or months of waiting for the final change, the transformation to the renewed, 
Fig. 77.—Adult worker (a) and larva 
( b ) of honey-bee. (Adult natural 
size; larva twice natural size.) 
Fig. 76.—Larva, pupa, and adult of 
the flesh-fly, Calliphora erythroce- 
phala , with complete metamor¬ 
phosis. (Two times natural size.) 
