24 OUR SHADE TREES AND THEIR INSECT DEFOLIATORS. 
produces a narrow, elongate band, which is then fastened at both ends 
onto the surface of the leaf by silky threads. Having secured itself from 
falling down by some threads, it now straddles this band and, bending 
its head downward (Fig. 8 6), makes a dive under it, turns a complete 
somersault and lies on its back, held down by the band (Fig. 8 ¢). By 
a quick turning movement the larva regains its feet, the band now ex- 
tending across its neck (Fig. 8d). It then adds to the band 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 an- 
terior or lower end of the collar, which thus rapidly grows in girth and 
is pushed further and further over the maker (Fig. 8 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 upright position (Fig. 7 
g and Fig. 8 f). When in motion or when feeding, the head and tho- 
racic segments protrude from the lower end of the bag, the rest of the 
body being bent upward and held in 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 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. Wheu kept in captivity the worms 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. 7 f). The worms un- 
dergo four molts, and at each of these periods they close up the mouth 
of their bags to remain within until they have cast their skin and re- 
covered 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 anearly 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 tho- 
racic joints are horny and mottled with dark-brown and white (Fig. 7 a). 
The numerous hooks with which the small, fleshy prolegson the middle 
and posterior partof 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. 7, f) is elongate-oval in shape, 
its outlines being more or less irregular on account of the irregularities 
in the ornamentation above described: The silk itself is extremely 
tough and with difficulty pulled asunder. 
