168 EN TOMOLOGY 
and body are compactly united; as distinguished from the free 
pupa of Neuroptera, Trichoptera, Coleoptera and others, in 
which the appendages are free (Fig. 203). This distinction, 
however; cannot always be drawn sharply. Diptera present 
also the coarctate type of pupa (Fig. 
Fic. 212. 
204), in which the pupa remains en- 
closed in the old larval skin, or pupa- 
rum. 
Pupal characters, though doubtless of 
great adaptive and phylogenetic signifi- 
cance, have received but little attention. 
Lepidopterous pupz present many puz- 
zling characters, for example, an eye- 
like structure (Fig. 213) suggesting 
Obtect pupa of milk- an ancestral active condition, such as 
weed butterfly, Anosia 
Pibe Due mabarali-cire. still occurs among heterometabolous 1n- 
sects. 
Pupation of a Caterpillar.—The process of pupation in 
a caterpillar has been carefully observed by Riley. The cater- 
pillar of the milkweed butterfly (Pl. 1, 4) spins a mass of 
silk in which it entangles its suranal plate and anal prolegs 
and then hangs downward, bending up 
the anterior part of the body (B), which 
gradually becomes swollen. The skin 
of the caterpillar splits dorsally, from 
the head backward, and is worked back 
toward the tail (C and D) by the con- 
tortions of the larva. 
Fic. 213. 
: : Head of chrysalis of 
The way in which the pupa becomes at- Papilio polyxenes, to 
tached to its silken support is rather com- 
plex. Briefly, while the larval skin still 
retains its hold on the support, the posterior end of the pupa 
is withdrawn from the old integument and by the vigorous 
whirling and twisting of the body the hooks of the terminal 
cremaster of the pupa are entangled in the silken support. At 
first the pupa is elongate (£) and soft, but in an hour or so 
show eye-like structure. 
Enlarged. 
