THE BAG-WORM 
259 
ward (Fig. 97 6), makes a dive under it, turns a complete somersault and lies on its 
back, held down by the band (Fig. 97 c). By a quick turning movement the larva 
regains its feet, the band now extending across its neck (Fig. 97 d). It then adds to 
the baud at each end until the two ends meet, and they are then fastened together 
so as to form a kind of narrow collar which encircles the neck of the worm. Far 
from resting, it now busies itself by adding row after row to the anterior or lower 
end of the collar, which thus rapidly grows in girth and is pushed further and further 
over the maker (Fig. 97 e). The inside of this bag is now carefully lined with an 
additional layer of silk, and the larva now marches off, carrying the bag in an up- 
right position (Fig. 96 g and Fig. 97/). When in motion or when feeding, the head 
aud thoracic segments protrude from the lower end of the bag, the rest of the body 
being bent upward and held iu this position by the bag. As the worms grow they 
continue to increase the bags from the lower end and they gradually begin to use 
d e f 
Fig. 97.— Thyridopteryx ephemerceformti. How the young larva prepares its bag. After Riley 
larger pieces of leaves, or bits of twigs, or any other small objects for ornamenting 
the outside. Thus the bags will differ according to the different kind of tree or shrub 
upon which the larva happens to feed ; those found on coniferous trees being orna- 
mented with the filiform pine leaves, usually arranged lengthwise on the bag, while 
those on the various deciduous trees are more or less densely and irregularly covered 
with bits of leaves interspersed with pieces of twigs. When kept in captivity the 
woitus are very fond of using bits of cork, straw, or paper, if such are offered to 
them. When the bags, with the growth of the larva, get large and heavy, they are 
no longer carried, but allowed to hang down (Fig. 96/). The worms undergo four 
molts, aud at each of these periods they close up the mouth of their bags to remain 
within until they have cast their skin and recovered from this effort. The old skin, 
as well as the excrement, is pushed out through a passage which is kept open by the 
worms at the extremity of the bag. 
The young larva is of a nearly uniform brown color, but when more full-grown 
that portion of the body which is covered by the bag is soft, of light-brown color 
and reddish on the sides, while the head and the thoracic joints are horny and 
mottled with dark-brown and white (Fig. 96 a). The numerous hooks with which 
the small, fleshy prolegs on the middle and posterior part of the body are furnished 
enable the worm to firmly cling to the silken lining of the bag, so that it can with 
difficulty be pulled out. 
The bag of the full-grown worm (Fig. 96/) is elongate-oval in shape, its outlines 
being more or less irregular on account of the irregularities in the ornamentation 
