160 ME.MOIUS OF THE XATIU.NAL ACADEMY' OF SCIENCES. 



variety is almost obsolete, and tlie black line is wanting. In Bnckler's tignies of tlie allied 

 dicta'oidcs there is only a luun[), ihulj;ing- by tlie liynies, none of tbe IJritish spceies seem 

 identical with ours. In Dnponcbel and Guenee's Iconograpliie et Distoire Naturelle des Chenilles 

 t. ii, the larva is very well fi<>iu'ed, but there is no horn, not even a marked latci-al blai-k line, and 

 the hump is not partiiulaily well developed. We have not seen other iigures of the European 

 caterpillar. 



Mr. Meske also wrote me in 1877 as follows: 



The imago of Xotodoiila riinona Packard stands very near to tlio Kuropcan Xulndnnla diclaa I-inur, but the 

 larv.'P of those two species ai'e entirely different. The larva of the former is very slender, light green, and has a 

 caudal horn like a sphinx larva; it feeds on I'opulus tremuloides. This is the second case in the North American 

 fauna where the imago stands very near to its allied European Ibrm, while the larva is entirely ditforent. The lirst 

 case 18 Acronijctn occidenialh as compared with Jcioni/cla psi Linne. 



It is well to keep the species thus distinct to em])hasize the fact that tlie full-fed European 

 larva is more like the younger stages, having lagged in its development behind the American 

 form. 



Dgg. — Diameter, 1.3 mm. Low hemispherical, about one-half as high as broad. Under a 

 Tolles triplet the micropyle in the center is distinctly seen, and the snow-white shell is distinctly, 

 though very finely, pitted or granulated. Under a i inch objective tlie markings are seen to 

 be very peculiar, the surface not being divided into polygonal areas, but studded with microscopic 

 beads, which form near the micropyle at the apex radiating series, and lower down lines of beads 

 more or less parallel with the equatorial diameter. From three to seven eggs are laid on a single 

 leaf. Probably the moth flies from one ])lant to another, laying a few eggs at a time. 



Freshly-hatched larva, Stat/c I. — Described a few hours alter hatching, before they began to 

 feed. Length, 3.5-4 mm. The head is rather large, shining black, smooth, and considerably 

 wider than the body; not spherical in shape, but somewhat flattened and subccnnlate or bilobed, 

 as the occiput is deeply indented. A large, broad, but antero-posteriorly rather short, black, 

 mostly smooth, prothoracic plate, with slight roughnesses near the front edge where the hairs 

 take their origin; the hinder edge slightly indented on the median line. On each side of the 

 l)late is a lateral black piliferous wart. The second and tliiid thoracic segments each with a pair 

 of conspicuous, oval, black, flattened, pililerous warts, and two small, round ones on each side, 

 the lower one being about one-half as large as the upper. Abdominal segments 1 to C each 

 with four dorsal, piliferous, flattened black warts, the hinder ones a little farther apart than the 

 anterior ones, hut yet close to the latter. On segment 7 the four corresponding warts are 

 arranged in a regular trapezoid, the two anterior ones being much nearer together than the 

 two hinder ones. On the eighth segment is a single central dorsal, black, oval, nnnlerately 

 prominent wart, which is twice as large as the largest on the ninth segment; it is transverse, 

 bearing a bristle at each end, thus having plainly originated from what was once two separate 

 warts. The latter segment bears four black warts, arranged in a regular trapezoid. The ninth 

 and tenth segments are held up when the larva walks. The anal legs are black and a little 

 smaller and shorter than the middle abdominal legs. The black suranal plate is subtriangnlar, 

 being obtusely pointed in front; the surface is rough, bearing a rough, low tubercle in fronton 

 which are minute piliferous warts. The body is somewhat flattened, being broader than high, 

 and of a ijcculiar, pale glaucous or sea green, the skin being polished like i>orcelaiii. 



The hairs under a .1 inch objective are seen to be slightly bulbous at the tip, and therefore 

 glandular, but under a lower power appear to taper like ordinary setaj. In Stage II the hairs 

 are also slightly bullions, and clear at the tij). 



At the end of IStaye J. — Length, o-(i mm. The body is much longer tiian before, so that the 

 tubercles are farther apart, ami now the eightli segment has the dorsal wart surrounded by an 

 amber-yellow spot, rendering it more conspicuous, and also the lateral concolorous line has 

 appeared; the same tint occurs on the base of the abdominal legs. 



(Specimens described in part from life, August 2.) Length at the end of the stage, just before 

 exuviation, mm. Tln^ head is moderately large, in the single larva oliserved not so wide as the 

 body, as it was about to molt, the jjrothoracic segment being greatly swollen. (In alcoholic 

 specimens the head and black piliferous tubercles of the larva in the next stage can be seen 

 through.) The head is now black and slightly bilobed, and L5 mm. wide. 



