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 hand, those
caterpillars known as 'silkworms' make a dense cocoon of pure silk,
consisting of two layers, the outer of coarse and the inner of fine
threads. Silken cocoons very similar in appearance are spun by the
larvae of small Ichneumon-flies. Many pupae lie in a loose cocoon formed
of a few interlacing threads, as for example the conspicuous black and
yellow banded pupa of the Magpie-moth (_Abraxas grossulariata_) and the
pupae of various leaf-beetles. Others again spin together the edges of
leaves with connecting silken threads. The grubs of bees and wasps which
are reared in the comb-chambers of their nests seal up the opening of
the chamber with a lid, partly silk (fig. 18 _co_) and partly excretion,