114 A1EMUIK8 OF THE NATIONAL ACADEMY OF SCIENCES. 



no\\' imicli inoro promini'iit. longer, aciite, especially those of the iufraspinicular series, those 

 on tlie hack of ahdoniiiiai segments S and (fig-. 4//) and those on each side of the suranal 

 plate, including the terminal ones. The two middle ones on the eighth segment are the 

 longest, being about three times as long as thick at the base, and nearly three times as long as 

 the median one on the nintli segment, while that on each side of the median spine is as large and 

 long as those on the side of t\w eighth segment. On the liase of the suranal plate is a trapezoidal 

 black patch. 



The body is yellowish green, with faint darker green longitudinal stripes. 



tStage IV. — Length, 15-:25 mm. Differing but slightly fi"om the previous stage. Width of 

 head, 2| mm. Prothoracic spines flatter, a little more button-like. The horns (PI. LII, tig. -i, 4r) 

 are somewhat stouter than before; early in the stage about as long as the prothoracic segment 

 is wide, but at the end not more than half as long as the bodj* is broad. The markings are as in 

 stage III, as also the granulations. T'he white stripes alternate with the dark-green ones, which 

 are quite distinct, the black spines being situated partly on them. The black plates on the end 

 of the midabdominal legs are well marked. 



Stage V and last. — Length, 43 mm. : width of head, 3f mm. The four prothoracic spines 

 are flattened, smooth on top, and the four black patches are wanting. The head is cherry-red 

 brown. The dorsal spines on all the segments (third thoracic and 1-7 abdominal), except the 

 second thoracic (PI. LII, fig. Aid), are not so high as broad and shorter than those of the infraspi- 

 racular series; but those on segments 8 and 9 are over twice as long as thick at })ase; the two 

 median spines on the eighth segment are longer than the suljdorsal one is .shorter than those on 

 the side. The suranal plate (PI. LIII, fig. 2r), is comparatively smootli abo\e. with four black 

 stout spines on each side and no dark discoloration near the base. 



The granulations on the skin of tlic body are coarser than in the earlier stages. Spiracles 

 t)lack. 



This only differs in coloration from tlic previous stage in wanting the dai-k patches on the 

 first thoracic segment, and the dark spot oti the suranal plate, while the green lines are a little 

 fainter; but the short lateral red stripes on abdominal segments 7-9 are as distinct. 



At the end of the stage when beginning to shorten preparatory to pupation some examples 

 ari' greener, the yellow being whiter and the green greener (Joutel). 



The fully fed caterpillar of this species may be distinguished liy its ]Kile-green iiody tinged 

 with whitish, and the seven darker green longitudinal stripes, while on the side of abdonnnal 

 segments 7-9 is a broad conspicuous cherry-red line situated below the spiracles, though owing 

 to the flattening of the body in these segments (a feature peculiar to this species) it can be seen 

 from abo^'e. The head is cherry-red, while the spines behind the horns are smaller than in the 

 other species of the genus inhabiting the United States. It is more nearly allied to the larva of 

 A. xoiatorla than any of the other species. 



It differs, however, from .1. soiaforia in coloration and the armature, besides being a smaller 

 larva. The four prothoracic dorsal spines are larger and better defined, those of A. .souitoriii 

 ))eing nearly obsolete. The horns are a little more primitive, being slightly divided at the tip, 

 while those of A. si'/nifor/n are .somewhat bulbous at the end. The spines of the segments behind 

 the horns to the 7th abdominal are slightly smaller and less stout, though of about the same 

 length; those of abdominal segments 8 and 9 are considerably slenderer, though scarcely shorter 

 than ^'1. seiuitoria. The lateral spines are slenderer than in the species mentioned, where thej' are 

 det'idedly stouter and more prominent. The anal legs are less coarsely spined than in A. soiatoria. 



The larvic of these two species are closely allied, and judging by them the two species probably 

 had a connnon origin, and since ^1. xeiHitor'm has larger, stouter spines, especially on the end of 

 the body, this species may be regarded as the more primitive one. judging by the freshly hatched 

 larva. 



Compared with the two other species, A. vl)'gi»i<msii< and A. stiguia. which are also closel\' 

 allied, A. ri(h!eitn<l<i and ^1. .'<cnatorla have a smaller head but stouter horns. The prothoracic 

 spines are nearly alike in all the species, l)ut in .1. riihici(ii(hi and ,1. xfiKilnrhi the dorsal spines 



