483 
[Packard. 
Mr. E. B. Poulton, and others, have given a fresh impetus to the 
study of the larval histories or ontogeny of Lepidoptera. The direct 
relation between nearly each step in the larval life of these insects 
and the temporary surroundings of the larva at different periods of 
its larval life have been forcibly impressed upon me by a more or less 
careful examination of the ontogeny of the Notodontians. More- 
over, a study of the rapid development and final suppression of cer- 
tain structural features, in the course of growth from the egg to 
the final larval stage has, in some cases at least, given a clew to 
the probable causes of variation and of adaptation in the Bomby- 
ces. Indeed, after tracing out the ontogeny of several genera of 
a family or sub-family group, one is impressed with the great fact 
which underlies these frequent and sudden changes of caterpillar 
habiliments, i. e., that a change of habit, due generally to a change 
of environment, induces change of structure, and not the reverse. 
These laws are perhaps more admirably exemplified in the life-his- 
tory of some other Bombyces than in the present genus and the 
group to which it belongs ; at the same time the larvae of the group 
of Platyptericidae are in some important respects very curious, and 
they differ in some interesting characters from the groups of Noto- 
dontidse and Bombycidse ( B . mori) between which they stand, both 
as regards their larval and their adult features. 
The larva of the present species in its final stage has been de- 
scribed by Mr. W. Beutenmuller, 1 who remarks that in this stage it 
“ lives singly on the upper surface of the leaf on a white silken web, 
slightly drawing the leaf together.” He found it on Betula alba. 
The late Mr. S. Lowell Elliot once informed me that it is in the habit 
of rolling up a leaf, and after eating a little of it, going to another 
leaf, cutting it and bending it over, and thus is quite destructive to 
the white birch. I found at Princeton, Mass., June 7th, several of 
the moths resting on the leaves of the common poplar-leaved birch 
( Betula alba var . populifolia) . A few days after capturing them, 
they laid their eggs on the sides of the box and on enclosed bits of 
paper in straight or curved rows of four or five, end to end. We have 
no observations on the mode of oviposition of our native species. 
All that I can find in European works is the following statement of 
Buckler, 2 referring to Drepana sicitla. “ The eggs are laid by the 
parent moth on the very edges of the leaves, so that when hatched 
1 Entomologica Americana, v, 38, Feb., 1889. 
2 The Larvae of the British Butterflies and Moths. Kay Society, 1889, III, 71. 
