8 
INSECTS IN GENERAL. 
THE METAMORPHOSES OF INSECTS. 
Nothing in the history of insects is more remarkable than the striking 
changes of form which many of them undergo, in the course of their 
development. Whilst other animals progress from infancy to maturity, 
simply by a process of growth, aud by such gradual and imperceptible 
changes only as their growth necessitates, many iuseets assume totally 
different forms in the course of their development, so that they could 
never be recognized as the same individuals, if this development had 
not been actually traced from one stage to another, these changes aie 
called the metamorphoses or transformations of insects. All insects, in 
their growth, pass through four stages, designated as the egg state ; the 
larva , or caterpillar state ; the pupa, or chrysalis state ; and the imago, 
or perfect and winged state. The metamorphoses of insects are of two 
principal kinds, complete and incomplete. 
In the complete metamorphosis the larva bears no resemblance to the 
imago, aud the insect, in the intermediate or pupa state, is motionless, 
and°takes no food. This kind of metamorphosis presents two principal 
varieties. In some (Lepidoptera and many Diptera), the legs aud wings 
are completely inclosed iu the pupa case. In others (Ooleoptera, Hy- 
menoptera, aud some others), the legs of the pupa, though useless, are 
free, and the rudimental wings lie loosely upon the sides. Moreover, iu 
some (the noctural Lepidoptera, and many Hymenoptera), the pupa 
is inclosed in a separate covering or cocoon, whereas the majority of in- 
sects have no such covering. Pupae thus inclosed are called folliculate. 
The term chrysalis, from a Greek word meaning golden, is sometimes ap- 
plied to the pupae of the diurnal Lepidoptera, because the pupae of some 
butterflies are ornamented with golden spots. 
Most insects, in changing from the larva to the pupa state, cast off the 
larval skin, but in many of the two winged flies, (Muscidse, Syriphidae, 
etc.) the larval skin becomes contracted and hardened, assumes "an oval 
form and a brown color, and thus forms a compact and closely-fitting 
case, in which the pupa proper is inclosed, but distinct. I’up® thus in- 
closed are called coarctate, aud their cases are analogous to the cocoons 
of the Lepidoptera. 
In the incomplete metamorphosis, the insect presents essentially the 
same form, aud is active in all its stages, after leaving the egg. I he 
pupa is distinguished from the larva by the presence of short rudimental 
wings at the base of the abdomen, and the imago or adult state is dis- 
tinguished by the fully grown wings and wing covers. It is only in this 
last stage that insects are capable of propagation. All the Homiptera, 
or bugs proper, and all the Orthoptera, or crickets, grasshoppers and 
cockroaches, exhibit this imperfect kind of metamorphosis. 
