THE CANADIAN ENTOMOLOGIST. 49 
ON THE EMBRYONIC LARVÆ OF BUTTERFLIES. 
BY SAMUEL H. SCUDDER, BOSTON. 
Reprinted from “The Entomologists Monthly Magazine,” Volume viii. 
In their papers on various species of British AZacro-Lepidoptera, Messrs. 
Hellins and Buckler furnish us with much better accounts of the external 
appearance of caterpillars than can be gained from the meagre and super- 
ficial descriptions which used to be thought sufficient ; and, as they have 
not confined their descriptions to the full grown animals, but have fol- 
lowed the creatures through all their moults, they have, in several cases, 
incidentally shown how great a difference there is between the larva just 
hatched and the full grown caterpillar ; especially in the case of some of 
the Rhopalocera thus treated by them. Mr. Riley, of America, has, in one 
or two instances, recorded similar facts. 
It is the purpose of the present communication to point out the pro- 
bable universality of this law—that caterpillars of butterflies present greater 
structural differences between tne embryonic and adult stages of the same 
‘individual, than are to be found in the adult larve of allied genera. By 
the term ‘embryonic,’ I designate those caterpillars which have not 
changed their condition since leaving the egg, a stage in which they 
generally continue but one or two days. Some of the changes alluded to 
are more or less gradual in their appearance, but they generally occur at 
the first moulting of the caterpillar. 
All the instances given are drawn from New England butterflies, and 
the generic terms employed are those used in my list, published in the 
Proceedings of the Boston Society of Natural History. If any one is 
sceptical in regard to the facts adduced, I can enter more into detail upon 
doubtful points. It should also be premised, that in studying caterpillars, 
the shape and sculpturing of the head, the form of certain segments, and 
especially the precise number, location and disposition of the spines, 
thorns, and hair-emitting warts of the body, will be found to furnish abun- 
dant means of distinguishing the most closely allied and minutely sub- 
divided genera. But to our examples. 
In the genus Satyrus, the body of the young larva is furnished with 
exceedingly long, scarcely tapering, compressed hairs, geniculate a little 
beyond the base, serrulate above, and generally directed backwards’; those, 
however, which occur on the upper portion of the thoracic segments are 
directed forward, and thus present a very peculiar contrast. Nothing of 
