OP ARTS AND SCIENCES. 81 



The head is large and full, rounded as usual in the family ; as 

 wide as or slightly wider than the body, i. e. the prothoracic seg- 

 ment, not taking into account the lateral tubercles. It is deep bright 

 brick-red ; the labrum, antenna?, and jaws yellowish. Tiie body grad- 

 ually tapers backwards from the head. 



The body is of a soft, pale greenish yellow ; the tubercles pale 

 yellowish, contrasting with the color of the body. The prothoracic 

 segment flares in front, the edge turning up and bearing two large 

 dorsal tubercles which are double. The prothoracic tubercles are very 

 prominent, projecting on each side, and are about twice as large as 

 the 2d and 3d thoracic ones, and bear twelve bristles. These tuber- 

 cles and those of the same series on the 9th abdominal segment are 

 much larger than the intermediate ones. There is a slight differentia- 

 tion in size and color of the dorsal tubercles, those of the thoracic and 

 9th abdominal segments being of the same size, and larger than those 

 on abdominal segments 1 to 7, and also of a deeper yellow shade. The 

 bristles are pale, those on all the thoracic tubercles, dorsal and lateral, 

 a little darker than those on the abdominal segments, and darker at 

 the tips. They are but little longer than the tubercles, and there are 

 about six on each abdominal tubercle. Under a half-inch objective 

 the bristles are seen to be not only docked at the tip, but the latter is 

 slightly but distinctly swollen or bulbous, and sometimes containing an 

 oval mass of the coagulated secretion. 



The median dorsal tubercle on the 8th abdominal segment is as 

 large as those on the thoracic segments ; it is twice as wide as long at 

 the base, and is more deeply divided than in any other of our Attaci 

 known, very plainly showing its origin from two originally separate 

 dorsal tubercles ; each fork is well developed, being about as long as thick, 

 and each bearing from 4 to 5 bristles. 



All the tubercles of the 9th segment are very large, about as large 

 as those of the thoracic segments. The suranal plate is large, nearly 

 equilaterally triangular, and bears near the apex two tubercles, each 

 of which gives rise to eight bristles ; they are smaller in proportion, 

 and nearer together, than those of O. promethea. 



The prothoracic segment is pale yellowish in front, chestnut-colored 

 behind, becoming blackish on the sides low down. At the base of 

 the lateral prothoracic tubercles are three black rings. On the side of 

 each abdominal segment 1 to 8 is a pair of parallel black slashes, situ- 

 ated between each of the upper and lower lateral tubercles ; on the 

 2d and 3d thoracic segments they meet on the middle of the back as 

 chestnut-colored stripes. On each side of the 9th abdominal segment 



VOL. XXVIII. (n. S. XX.) 6 



