OF ARTS AND SCIENCES. 79 



veloped on the abdominal segments as on the tlioracic. The tho- 

 racic tubercles also are no more differentiated than the abdominal 

 ones. Samia also differs from Callosamia in the twelve rows of 

 black spots along the body. The larva of Samia is thus seen to be 

 intermediate between Platysamia and Callosamia, but the moth is 

 apparently intermediate between Callosamia ( G. angidifera) and 

 Attacus. 



The head and the shape and size of the body of the larva are like 

 those of Callosamia, but in its secondary adaptive generic characters 

 it retains a resemblance to Platysamia. In a systematic classifica- 

 tion, then, we had better adopt the imaginal characters rather than the 

 larval, the latter being so much more plastic and more readily influ- 

 enced by changes in the mode of life and by differences in the food. 

 In its earliest larval stages, the insect is certainly more like Platy- 

 samia cecropia than Callosamia, but still even in these stages Samia 

 is more advanced than Platysamia, which in its earliest larval stages, 

 especially in the possession of long bristles arising from the short tu- 

 bercles, intergrades with or is closely allied to the fully grown larva of 

 Saturnia carpini ; and in the imaginal characters Platysamia is nearer 

 the ancestral form Saturnia (in the restricted sense) than to any of the 

 other Attaci. If we do as we should do in locating Samia in its 

 proper taxonomic position, we shall not err greatly in placing Samia 

 much above Cecropia, and on the whole near Attacus. 



Larva of Attacus sp. (possibly A. splendidus DeB.). 



The larva of which I give the following description was collected at 

 Socorro, Arizona, September 9, 1874, by Wheeler's Expedition. The 

 single specimen was in alcohol. It is probably about half grown. 

 (Plate II. Figure 7.) 



Length 25 mm. Head rather large, slightly more than one half as 

 wide as the body when it is thickest ; it is of a chestnut color, smooth, 

 not hairy. The body is moderately long and quite thick and fleshy, 

 tapering rather rapidly behind. The prothoracic segment is granu- 

 lated above, but with no tubercles ; on each side, however, is a 

 remarkably long fleshy tubercle or process, which hangs down and 

 curls back like a ram's horn, and is finely spinulose ; it is about as 

 long as the segment is thick, and is situated exactly in front of the 

 spiracle of the same segment. On each of the 2d and 3d thoracic 

 segments is a pair of short thick tubercles, those on the 3d a little 

 longer than those on the 2d segment. On each side of these seg- 



