TWO INSECTS OF THE ORCHARD — SNODGRASS. 489 



the fall perforation of the leaves we first noticed. In order, there- 

 fore, to make a single narrative out of a double story, let us resume 

 our history with those caterpillars that mature in the autumn. 

 Some of these cease feeding during the latter part of September 

 while others keep on till the last week of October. But, at some time 

 during this period, there comes a prompting to the caterpillar to do 

 an act it has never done before, an act which it has even carefully 

 avoided doing up till now. This is to bite a hole through the wall 

 of its mine. The hole is not a careless puncture but is made de- 

 liberately and so placed, in the large end of the mine, that a cres- 

 centic line drawn through it would leave plenty of space for a 

 similar reversed crescent on the same surface with the concave 

 edges toward each other. The caterpillar next proceeds to lengthen 

 the hole into a slit, following this imaginary crescentic line, and 

 then cuts a corresponding slit in the opposite wall, after which 

 it carries the two along together till there is formed perhaps an 

 almost semicircular incision through both surfaces of the leaf. The 

 caterpillar all the while works from the concave side of the cut 

 and, in order to hold the two resulting flaps in place, sews their 

 lips together as the work progresses, with threads of silk spun from 

 the spinneret. 



A caterpillar at work on an incision like this was watched till the 

 job was finished in order to get a complete report on the procedure. 

 Having finished the crescent, the worker continued the cutting from 

 one end of it toward the other in a corresponding reversed crescent, 

 herself between them, till she had thus all but severed two small, oval 

 disks which finally remained attached to the rest of the leaf by only 

 a slender tongue from the lower one. Two hours and fifteen minutes 

 had elapsed since the start, but as the cutting progressed the cater- 

 pillar frequently interrupted it to stitch the severed edges together, 

 so that, at this stage she was inclosed in a little case made of the two 

 leaf disks fastened together along the sides but open at each end. 



With the case thus all but free from the leaf, the caterpillar turned 

 about and occupied herself with further sewing within. But after 

 a few minutes she came back and gnawed very carefully at the con- 

 necting strap, reducing it to such a narrow width that it looked as 

 if the little piece must certainly drop out. But it did not, and the 

 caterpillar returned to her sewing. Presently, however, she reverted 

 to the attachment and this time reduced it to the merest shred. Yet 

 the case did not even sag. The caterpillar again went about her spin- 

 ning with no outward mark of excitement or of apprehension, though 

 her habitation hung by a thread. At length she came once more to 

 the edge, felt slowly along the lower lip till the connecting strand 

 was located, and with a clip or two of her jaws severed it. Nothing 

 happened ; the shell remained in place, held in its frame by the tangled 



