1833.] -Lt)! [Packard. 



lower edge above the plaiita is a group of seven or eight minute spines ; 

 a similar group of minute spines occurs near the end of the middle abdomi- 

 nal legs. 



For the colors the reader is referred to the description and figure by 

 Riley, of the living animal, in the American Entomologist, i, 230. We 

 have not yet seen a full-grown living larva. The foregoing description 

 has been drawn up from four well-preserved alcoholic specimens. 



This larva differs genericallj'- from Eacles in having well-developed 

 dorsal spines on the prothoracic segment ; while the lateral ones along 

 the abdominal region are also well developed, these being nearly obsolete 

 in Eacles. The genus Citheronia is unique in having seven spines on 

 the eighth and the ninth abdominal segments respectively. All these 

 characters are seen to be secondary and adaptive, and yet they are good 

 generic characters, showing that the acquirement or loss of generic char- 

 acters is due to adaptations to the surroundings. The specific characters 

 are well brought out by comparing O. regalis and G. sepulcralis. 



RECAPITULATION OP THE SALIENT FEATURES IN THE ONTOGENY OF 



CITHERONIA. 



A. Congenital Characters of the Larva, as seen in Stage 1. 



1. The three pairs of enormous spines ; the first or prothoracic pair but 

 little shorter than the third, and the middle pair about two-thirds as long 

 as the body, all ending in a swollen, triangular, two-horned flattened 

 bulb ; these appendages being deterrent and for offensive use in the earliest 

 as well as latest larval life. 



2. Both the eighth and ninth abdominal segments bearing a high 

 median dorsal horn ; and these segments bearing seven, instead of only 

 five, spines. 



3. Tlie lateral spines on the abdominal segments nearly as large as the 

 dorsal ones. 



4. Body dark ; head dark in color. 



B. Evolution of Later Adaptational Characters. 



1. The bulbous tips of the thoracic horns dropped at the end of Stage 



11 (?). 



2. The thoracic horns become curved in Stage II or III (?). 



3. The thoracic dorsal spines become much stouter, w^ilh much shorter 

 and stouter spinules at the last molt. 



4. The mature larval features mostly assumed in Stage III. 



5. The dark colors exchanged after the last molt for pale green, with 

 bluish tints. 



6. The black dorsal thoracic spots and the lateral yellowish bauds most 

 showy in the last stage. 



Attention should be drawn to the colossal size of this larva, as compared 

 with that of Sphingicampa and even Eacles, though the head is not so 



PROC. AMER. PHILOS. SOC. XXXI. 141. V. PRINTED MAY 10, 1893. 



