Packard.] THE POPULATION OP M APPLE TREE. 189 
rous with the wings. On the top of the head is a conspicu¬ 
ous bushy tuft of bright reddish orange hairs. The legs are 
of a leaden hue, the hairs yellowish, the hind shanks long 
and hairy, with four long, slender spurs; the antennae are 
dark on the terminal three-fourths, pale orange at base. 
The under side of the wings are leaden gray. The length 
of the body is # 07, and of the body including the folded 
wings, one-tenth of an inch. 
The Sac Bearer .—Another winged gem, with a still more 
curious childhood than the Micropteryx, is a sac bearer, as 
the Germans call it. Like a boy in a meal sack, with his 
arms sprawling about and pulling himself along, the little 
caterpillar pokes its head out of its case, extends its six fore 
legs, like so many hands, and pulls itself over the leaf, its 
little world. The worm is flattened, green, and no thicker 
than a small knitting needle. The case or sac is oval, open 
at each end, much flattened and room}' enough for its inhab¬ 
itant to turn around in. How the case is constructed we 
have been unable to observe. While some sac bearers cut 
an oblong slit in the leaf, fold it over, and then cutting a 
corresponding slit remove the folded portion, fasten together 
with silk the open side, wriggle into this straight jacket, and 
walk off as if they had been born with their houses on their 
backs ; others probably construct their cases out of fine bits 
of leaf stuck together with the silken glue secreted from the 
glands emptying into their mouths. The material of such 
cases resembles a thick, felt-like cloth, and that of our sac 
bearer is of this nature. By the end of August the caterpil¬ 
lar becomes mature and ready to transform into a chrysalis. 
It does not desert its old coat, but hangs it by a few threads 
to the bark of the tree and contracts its body, lies quiet 
through the winter, until early in summer the chrysalis 
breaks through a rent in its skin and soon after the moth 
appears. It is now one of the most beautiful objects in 
nature. It is very small, the head finely dusted, its softly 
29 
