MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 43 



n. EVOLUTION OF LATKR ADAPTATIOXAL CHARACTEiJS. 



1. Dorsal tubercles in Stage II higher than before. 



2. The lateral dark band disapi^ears iu Stage II. 



3. In Stage III the dorsal thoracic tubercles become nearly twice as long and thick as, the 

 abdominal ones. 



i. The head is not banded iu Stage IV. 



5. The tubercles brightest (pink or dark carmine) and most conspicuous in the last stage. 



0. A distinct iufraspiracular yellow line in Stage IV, and the suranal plate and anal legs lined 

 with yellow, and the surface of the suranal plate and sides of the anal legs amber-colored. 



Family Cochliopodidw. — The slug like larv?e of the Bombycoid family Cochliopodid;?, so 

 remai'kable from their snail-like mode of locomotion, their abdominal legs being entirely atroi)hied, 

 in their life history offer strong circumstantial evidence in favor of tlie primitive rapid acquisition 

 of striking characteristics at the first molt. These larvfe, as we have elsewhere stated, are born 

 ■without traces of abdominal legs, are nearly colorless, and with bodies more cylindrical than in the 

 full grown caterpillar. In the more specialized tuberculated and spiny genera Adoneta and Empre- 

 tia (and probably Euclea) the tubercles are already differentiated in Stage I, much as in the last 

 stage, but otherwise the change from the first to the second stage is very great, so that the set of 

 «07igenital characters is very different from the assemblage of acquired characters, especially the 

 addition of great nnnibers of bristles on the tubercles, and the gay varied colors and markings of 

 the body. This sudden change, after but a single molt, shows that these characters are suddenly 

 acquired. The larv?e from being minute, pale-yellowish worms, hatching from almost invisible 

 scale-like transparent eggs, after the first molt undergo a striking change, the result of feeding in 

 a more exposed situation and of consequent successful adaptation to prevent recognition on the 

 part of hostile insects and birds. The armature of poisonous glandular spines and the development 

 of b/i'ight warning colors are evidently characters acquired late in larval life, when the creatures 

 are large enough to attract notice. 



In illustration of the changes due to adaptation undergone by members of this family, I have 

 selected the following examples, copied from a previous paper:' 



RECAPITULATION OF THE MORE SALIENT ONTOGENETIC FEATURES OF EMPRETIA STIMULEA. 



A. CONGENITAL FEATURES. 



1. The tubercles on the second and third thoracic and the first, seventli, and eighth abdominal 

 segments three times the size of those on abdominal segments 2-6, these tubercles being already 

 differentiated at birth and more markedly so than in Adoneta. 



2. Head not capable of being withdrawn into and concealed by the prothoracic segment. 



3. The tubercles each bear only three two-forked glandular setie. 



4. The body is more cylindrical than in the later stages and colorless. 



B. EVOLUTION OF ADAPTATIONAL FEATURES. 



1. In stage II the form and general colors of the full-fed larva are assumed. 



2. The tubercles are now armed with numerous poisonous spiuules. 



Note.— From what we now know of the congenital as compared with the later acciuired adaptational characters 

 ■of Cochliopods, it is evident that the latter are acquired at an earlier stage than in most other caterpillars. 



RECAPITULATION OF THE MORE SALIENT ONTOGENETIC FEATURES OF ADONETA SPINULOIDES. 



A. CONGENITAL FEATURES. 



1. No tubercles on the prothoracic segment. 



2. The dorsal tubercles on the second and third thoracic and first, fourth, seventh, and eighth 

 abdominal segments double the size of those on the other segments, the tubercles being already 

 differentiated at birth. 



' Proceedings Amer. Philosophical Society, Phil, xxxi, pp. 83-108, 1893. 



