12 PROCEEDINGS OF THE NATIONAL MUSEUM vol.71 



In feeding, the caterpillars always first attacked the terminal buds 

 and then ate downward along the stem. The leaves were scarcely 

 touched until after the first spring molt. 



All of the caterpillars molted on March 8 and 9 — that is, 1 1 or 12 days 

 after having been brought from hibernation. 



As the caterpillars increased in size they fed with avidity, consum- 

 ing larger and larger leaves. But one by one they all died off. A 

 single one suspended itself for pupation on April 2, but died without 

 casting its larval skin. 



This single northern caterpillar therefore molted once between 

 hibernation and pupation, as described by Mr. Scudder. 



On May 10 we visited the locality beyond the Cabin John Bridge, 

 but could find no traces of caterpillars. On May 31, however, cat- 

 erpillars of various sizes were found in great abundance on all the 

 plants near the large patch of turtlehead, on ferns, grasses, ash, elder, 

 Viburnum, willow, cat-tails, etc., but especially on the dead dry leaves 

 and stalks of cat-tails and grasses and the dead last year's stems of 

 various herbaceous plants. One hundred and eleven caterpillars were 

 collected without apparently reducing their numbers. 



The caterpillars varied very greatly in size. Many appeared to 

 be fully grown, but a few were scarcely larger than the normal size 

 after the first spring molt. Several were found suspended from a 

 silken button preparatory to pupation; two of these cast the larval 

 skin during the ride home. 



The largest caterpillars were placed in four boxes of 25 each. 

 About one-third pupated at once, but nearly all the pupae were at 

 once attacked by the other caterpillars. In one box 10 out of 12 

 pupae were more or less bitten, usually in the anterior half of the 

 ventral surface, and one was almost completely devoured, only a few 

 empty abdominal segments remaining. 



Much to our surprise, the caterpillars which did not pupate molted 

 again. All of the caterpillars brought back were of approximately 

 the same size, and were all, we thought, fully grown, as in the field a 

 number were already suspended for pupation. 



All of the butterflies from the caterpillars found suspended in the 

 field as well as from those that pupated in the boxes were males. 



We tried feeding the caterpillars on Wisteria, which they would not 

 touch, and on Lonicera japonica, which they ate, though not with 

 relish. Chelone they recognized at once and eagerly devoured. 



In the field we have found the caterpillars on the leaves of ash and 

 of Viburnum which they had eaten in their characteristic way by 

 cutting in from about the middle of the side. 



Our belief is that after hibernation, as well as before, these cater- 

 pillars normally feed only on Chelone. But they visit this plant only 



