36 MEMOIES OF THE NATIONAL ACADEMY OF SCIENCES. 



ACQUIRED CHARACTERS IN THE NOTODONTID.E. 



lu tlie succeeding systematic poitioii of tliis work I have siveii a number of life histories of 

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

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

 tubercles and setiB in the larvae of the Bombyces and other of the higher Lepidoptera and to their 

 probable mode of origin and why they appear on certain segments in preference to others. The 

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

 history of Datana intcgerrima, Apaielodes torrefacta, Symmerista albi/rons, Macrurocampa marihesia, 

 and of three species of Centra, while there is a summary of the steps in the assumption of the 

 adaptive characters at the different larval stages of several species of Schizura. The steps in the 

 evolution of what maybe regarded as acquired characters in Schizura, and in DasylopMa angiiiiia 

 Hyparpax, Ileterocampa, etc., are leadily seen by an examination of the plates. 



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

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

 larvfc 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 cuticle or outgrowths of the entire integu- 

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



Take for example the larval JSFadata (jibhosa; this, like the caterpillar of Gluphisia and of 

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

 history of JV. fiibhosa 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 spines so frequently observed 

 in the grouti arose within recent geological times, and weie acquired during the postembryonic 

 stages of the larvae of different genera in response to various changes in the surroundings of 

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

 development, resulting in a series of forms constituting the i^resent 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 Iletirocannja hiundata. During the three earliest stages 

 the larva bears on the i»rothoracic segment a pair of enormous antlers with four tines. At the 

 second molt these ai-e 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 difterent 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 the caterpillar of Heterocainpa (/uttivitta, 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 spines on abdominal segments 1 to G and also 8 and 9, 

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

 the most singular larvae 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 pair of knob like tubercles, the other segments, however, 

 showing no trace of the former existence of spines. Also, while the body was not striped iu 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 efl'aced 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 anticipations of the 

 markings of the fully grown caterpillar. In the present 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 ami 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. oUiqua, its horns being like those of H. gut- 

 iivitta (III«), and also dropped at the first molt. 



