the Coleoptera, Neuroptera, Trichoptera, Hymenoptera
and many Diptera. In some cases the pupa requires to be specially
adapted for a peculiar mode of life; for example, a special arrangement
of breathing organs may be necessary for life under water, and there
must needs be temporary pupal structures, not represented in the imago.

On the other hand, in the pupae of most Lepidoptera and of some Diptera,
there is more or less coalescence between the cuticle of the appendages
and the cuticle of the body generally, so that the appendages do not
stand out, but being, as it were, glued down to the body, are somewhat
masked (see fig. 1 _e_ and fig. 23). Consequently the _obtect_ pupa, as
this type is called, does not resemble its imago as fully as a free pupa
does. The outline of the wings for example in a butterfly's pupa can in
some cases be traced only with difficulty. T.A. Chapman has shown (1893)
that the completely obtect pupa characterises the more highly developed
families of Lepidoptera, while in the more primitive families the pupa
is incompletely obtect. If the pupa of a butterfly or moth be lifted and
held in the hand, a bending or wriggling motion of the abdomen can be
observed. In the incompletely obtect pupa, this motion is evident in a
greater number of segments than in the completely obtect, the number
concerned varying from five to two in different families. In the
nymphalid butterflies, the pupa is often called a 'chrysalis' on
account of the golden hue displayed by the cuticle, and the term
'chrysalis' is sometimes bestowed indiscriminately on any kind of pupa.
It has been shown by Poulton (1892) and others, that the colour of a
butterfly pupa is to some extent affected by the surroundings of the
caterpillar just before its last moult.

Reference has been made (p. 58) to the power of spinning silk possessed
by many larvae; often the principal use of this silk is to form some
protection for the pupa, the larva before its last moult constructing a
_cocoon_ within which the pupa may rest safely. Many larvae bury
themselves in the earth, and the pupa lies in an earthen chamber, the
lining particles of soil fastened together by fine silken threads.
Larvae that feed in wood, like the caterpillar of the Goat-moth (Cossus)
make a cocoon of splinters spun together, while hairy caterpillars, such
as those of the Tiger-moths, work some of their hairs in with the silk
to make a firm cocoon (fig. 17 _b_). On the other h