MEMOIES OF THE NATIO^TAL ACADEMY OF SCIE>5^CES. 
33 
V.— ON THE INHERITANCE OE ACQUIRED CHARACTERS IN LEPIDOPTERA. 
Perhaps iu no other group or order of animals may we study the subject of the inheritance of 
acquired characters with more success than in the Lepidoptera. In these insects the four stages 
of existence — the egg, larva, pupa, and imago — are definite and fixed, and during eacli of the three 
last periods the organism is, so to speak, a different creature, with distinct and separate shape 
and structure, external and internal, and during each leads a different life. Family, generic, and 
specific characters are inherited at each of these stages, and at each there is a combination of 
congenital and acquired characteristics, some of both classes of which, i. e., those least marked, 
are difficult to separate from each other. 
The following is an attempt at a rough grouping of such features at; the last three stages. AVe 
omit the egg stage, for though they more or less vary in shape and ornamentation, this is perhaps 
due more to difference in the structure of the lining of the oviduct of the female than to the action 
of external circumstances on the egg after it has been laid. Yet this should be said with some 
reservation, because we are not aware that any one has discussed the probable mode of origin of 
the specific ditt'erences in the shape and color of the eggs of birds or the shape and markings of 
the eggs of insects, though undoubtedly the agency of external causes, together with natural 
selection, has had something to do with the variation. 
It has seemed to us that the relation of specific and generic characteristics in the eggs of 
insects is a most difficult problem. Yet it should be observed that while the difierences in orna- 
mentation and shape are primarily due to the impression on the shell received from the lining of 
the oviduct, yet the wonderful diversity we see in the eggs of insects is often readily seen to be 
correlated with the external conditions in which they exist after having been deposited by the 
parent. In birds the thick, solid shell and the oval shape of the mnrre’s egg seem due to the 
unprotected manner iu which they are left on the rocks and shelves, from which they are liable 
to fall. 
AVe may contrast with such an egg that of the robin, in which the shell is tliin and uniform 
in color, since it is protected from harm by being contained in a nest; so also the color of the 
murre’seggs may be due to the action of protective mimicry, the spots assimilating them to lichen- 
grown rocks, by which they escape the observation of their natural enemies, the fox, the mink, 
and other egg- devouring animals. So the eggs of Chrysopa, of many bugs, etc., ai‘e in shape and 
mode of attachment beautifully adapted to prevent them from being seen by egg-devouring 
animals. 
In the larval histories given in this work we have endeavored, where they have been observed 
with sufficient completeness, to discriminate between the congenital and the acquired characters. 
1, Larval state. — A. Iu this state we have the inheritance of congenital characteristics. 
B. Inheritance of what wei*e originally acquired characters, the results of attacks of enemies: 
Examples are the tubercles armed with spines and sometimes with caltrops (Empretia, etc.) and 
stripes, all apparently inherited at different periods of larval life, the least important specific 
and varietal characters probably having been acquired during the life of an .individual. 
Fit^a state, — A. Cocoon: The absence or presence of a cocoon was doubtless originally due 
to differing external conditioiis, while the dense, perfect cocoon is characteristic of the spinning 
moths (Attacidm, Lasiocainpitlm, etc.) ; the Ceratocampidie make none at all, but, like the Sphinges, 
the larvm simply bury themselves in the earth before pupation. In the Arctiidm and the Lipa- 
ridic the cocoon is chiefly composed of the barbed larval Lairs, with a little silk to fasten them 
more firmly together; in theGeonietridre certain larvie spin a loose, thin web. In such cases the 
spinning of a cocoon is intimately associated with a change of larval liabits, and is, with little 
doubt, an acquired habit, originally formed by a single individual. 
B. The shape of the pupa is often dependent on the presence or absence of a cocoon. In the 
E'otodontidm the cremaster is often absent in genera such as Gluphisia, which spins a very slight 
cocoon, and Lophodonta, which spins no cocoon, and is closely allied to those which do. In 
Cerura there is no spine on the rudimentary cremaster, because the pupa lies in a very dense 
cocoon fastened to the bark of trees, etc., and being in no danger of being shaken out no cremas- 
S. Mis. 50 3 
