36 
MEjMOIRS of the natio^s^al academy of sciences. 
ACQUIRED CHARACTERS IN THE NOTODONTIDiE, 
In the succeeding systematic xioition of this work I hfive given a number of life histories of 
the family, and with more or less detail pointed out the later adaptional as distinguished from 
the congenital characters. I have on pages 21-23, called attention to tlie varying shapes of the 
tubercles and seta‘- in the larvic of the Bombyces and other of the Ingher Lex»idoi)tera and to their 
probable mode of origin and wby they appear on certain segments in ])refereuce to others. The 
attention of the reader is called to the summary or recapitulation of changes especially in the life 
history of l>ata7ia mtefferrima, ApateJodes iorrefactn, Sym^nerhia albi/ro7is, Macrii7'oca7npa mm^thesia^ 
and of three species of Cenira, while there is a summary of the steps in the assumiition of the 
adaptive characters at the different larval stages of several sjiecies of Schizura. The steps in the 
evolution of what maybe regarded as acquired characters in Schizura, and in Dasylophia angxiina^ 
Hypaiqiax, neterocamxia, etc,, are readily seen by an examination of the plates. 
The Notodontiaus are remarkable in general for the humps, tubercles, and spines of their 
larvm, some of which are congenital, while others appear at different stcUges after birth. Still some 
larvm of this group are entirely without them and remain so throughout their larval life. And 
this is an argument tliat the various processes of the cuticle or outgrowths of the entire integu- 
ment are characters originally acquired during the postembryonic life of the young insect. 
Take for examxile the larval Nadata gibhosa] this, like the catciqullar of Gluphisia and of 
Loidiodouta, is a smooth-bodied larva, ornamented with lines, but entirely unarmed. The life 
history of A. gibbosa shows that it is born with a smooth body, without any traces of tubercles or 
enlarged bristles, while no traces of the yellowish subdorsal lines appear until at the end of the 
second stage, the only ornamentation being coloration. This form is therefore a primitive one, and 
•this fact would seem to demonstrate that the humps, tubercles, and s])ines so frequently observ^ed 
in the group arose within recent geological times, and were acquired during the postembryonic 
stages of the larvm of different genera in response to various changes in the surroundings of 
different species, these finallj' becoming fixed and regulaiiy transmitted along various lines of 
■development, resulting in a series of forms constituting the luesent genera of the family. 
One of the most notable cases in the family is that of the loss at about the middle of the 
larval life of the remarkable antlers of lleteroccunpa hiimdaia. During the three earliest stages 
the larva bears on the prothoracic segment a pair of enoimious antlers with four tines. At the 
:secoiid molt these are discariied, and in the two last stages are represented by a pair of conical, 
rounded, polished, piliferous knobs. The rest of the partly grown body of the larva is smooth. 
After casting its horns the larva assumes a new set of coloration markings, so chat in its last 
two stages it is a totally different creature in appearance from the earlier stages. 
One of the plates represents a scries of colored drawings, by Mr. Bridgham, of the still more 
wonderful changes undergone by the caterpillar of Heterocampa guttivHia^ representing five 
stages, nearly each of which jiresents notable differences. In tlie iirst, direct!}' after hatching, 
the reddish larva has not only a pair of enormous antlers with four tines on the first thoracic 
segment, but a i)air of long antler-like spines on abdominal segments 1 to 0 and also 8 and 0, 
those on segments 1 and S being about three times as large as the others. It is certainly one of 
the most singular larvm of the family. 
Now this bizarre armature is entirely discarded at the first molt, with the exception that the 
prothoracic antlers are reiiresented by a pair of knob-like tubercles, the other segments, however, 
showing 110 trace of the former existence of spines. Also, while the body was not strijjed in Stage 
I, it is now paler red, with a more brownish tint, and Is marked with four yellowish stripes. At 
the end of this stage the lines become eifaeed and the bo<iy grows more yellowish on the sides, 
III the third stage the tubercles still persist, but the markings differ very much, as reddish dorsal 
liatches appear in the middle and near the end of the body, and there are anticipations of tlie 
markings of the fully grown caterpillar. In the jiresent stage the insect closely resembles the 
mature larva, having bright crimson markings ou the thoracic segments and on the third and 
fourth and ou the fifth and sixth abdominal segments, these bright spots becoming somewhat less 
decided and conspicuous in the final stage. 
Fig. 1 (p. 37) represents the first larval stage of H, obliq^ia^ its horns being like those of H, gut- 
tivitia (IIIu), and also dropped at the first molt. 
