36 WEMOIKS OF TliE NATIONAL ACADEMY OE SCIENCES. 



ACQUIRED CHARACTERS IN THE NOTODONTID/U. 



In the succi'C<liiig systematic jjoi tioii of tliis work I have niveii a imiiiher of life histories of 

 the family, and with more or less detail pointed out tlie later adaptional as distinj;;uished from 

 the congenital characters. I have on pages 21-23, called attention to the varying shapes of the 

 tubercles and seta- in the larva' of the Bombyees and other of the higher Lei)ido])tera and to their 

 probable mode of origin and Avhy they appear on eertain segments in [yreference to others. The 

 attention of the reader is called to the summary or recapitulation of changes especially in the life 

 liistory of Datana intcf/errima, Apntehulets iorrefacta, Symmerista albifrons, ^facnlroc((mp^ martlicsid, 

 and of three si)e('ies of Ceriini, while there is a summary of the steps in the assnmi)ti()n of the 

 adaptive characters at the different larval stages of several si>ecies of Sehizura. The steps in the 

 evolution of what maybe regarded as ac(iuired characters in Schizura, and in DanyJophia Huguiua 

 Hypari)ax, lleteiocanipa, etc., are readily seen by an examination of the plates. 



The Notodontians are remarkable in general for the humps, tubercles, and spines of their 

 larva>., some of which are congenital, while others appear at different stages after birth. Still some 

 larvar of this group are entirely without them and remain so throughout their larval life. And 

 this is an argument that the various processes of the cutit-le or outgrowths of the entire integu- 

 ment are characters originally acquired during the postembryonic life of the young insect. 



Take for example the larval Nadata gibhosa; this, like the caterpillar of Gluphisia and of 

 Lopliodonta, is a smooth-bodied larva, ornamented with lines, but entirely unarmed. The life 

 history of N. (libbosa 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 forju is therefore a ]irimitive one, and 

 this fact would seem to demonstrate that the humps, tubercles, and spines so fre(piently observed 

 in the group ai'ose within recent geological times, and were acquired during the postembryonic 

 stages of the larva> of different genera in response to various changes in the suiToundiugs of 

 different species, these finally becoming fixed and regularly transmitted along various lines of 

 ■development, resulting in a series of forms constituting the present 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 Hetcrocampa biiunluta. During the three earliest stages 

 the larva bears on the prothoracic segment a pair of enormous antlers with four tines. At the 

 second molt these are discarded, 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 that in its last 

 two stages it is a totally different creature in appearance from the earlier stages. 



One of the plates represents a series of colored drawings, by Mr. Bridgham, of the still more 

 wonderful changes undergone by tlic caterpillar of Heierommpa fiKttlvitfa, representing five 

 stages, nearly each of which presents notable differences. In the first, directly after hatching, 

 the reddish larva has not only a pair of enormous antlers with four tines on the first thoracic 

 segment, but a pair of long antler like si)ines on abdominal segments 1 to (! and als(t 8 and 9, 

 those on segments 1 and 8 being about three times as large as the others. It is certainly one of 

 the most singular larviB of the family. 



Now this bizarre armature is entirely discarded at the first molt, with the exception that the 

 prothoracic antlers are represented by a jiair of knob like tubercles, the other segments, however, 

 showing no trace of the former existence of spines. Also, while the body was not striped in Stage 

 I, it is now paler red, with a more brownish tint, and is marked with four yellowish strijjes. At 

 the end of this stage the lines become effaced and the body grows more yellowish on the sides. 

 In the third stage the tubercles still persist, but the markings differ very much, as reddish dorsal 

 patches appe ir in the middle and near the end of the body, and there are anticipati(ms of the 

 markings of the fully grown caterpillar. In the ])resent stage the insect closely resembles the 

 mature larva, having bright crimson markings on the thoracic segments and on the third and 

 fourth and on the fifth and sixth abdominal segments, these bright s2)ots becoming somewhat less 

 decided and (!onspicuous in the final stage. 



Fig. 1 (J). 37) Hipresents the first larval stage of H. obliqua, its horns being like those of H. gut- 

 tivitta (Ilia), and also dropi)ed at the first molt. 



