MEMOIRS OF THE iSTATIOi^AL ACADEMY OF SCIENCES. 197 



dasli in front, but in tlie present stage these daslles are strengtbened, united, broader, and 

 colored mure distinctly.) 



A noteworthy step taken at this stage is the tiual consolidation of the two dorsal tubercles of 

 the lirst abdominal segment, which now becomes a forked single tubercle. 



Fiiurth utiifjr, after the third molt. — Observed August (i. Length, 15-10 mm. The characters 

 of tlie full fed larva are now almost wholly assumed. The head is high aud narrow, the vertex 

 bearing two tubercles. The forked tubercle on the first abdomiual segment is now larger and 

 higher than that on the eighth segment; all are reddish, tipped with black. The body is much 

 thicker than before and uuirbled, except on the pale pea-green nieso- and metathoracic portions, 

 with reddish lines and spots, which are much more numerous than before. The hairs are now 

 entirely changed in shape, being simple aud pointed like those ou the head. 



Fifth ■st(u/e, after the fonrth molt. — Observed August 10-18. Length, 2~>-2'i mm., and finally 

 35 mm. This stage does not dift'er essentially from the fourth, except that the horns are a little 

 higher. The markings and colors of the mature larva seem to be acqidred in this stage. 



The essential or specific characters may be best brought out by comparison with the 

 fully grown larva of S. unicornis. S.iponica' is larger and the hairs are longer. The head is 

 less angular above aud not so strongly marbled with the irregular network of reddish lines, and 

 has four dark lines in two pairs extending from the vertex to the base of the mandibles. The 

 arrangement of the four double red and yellow dorsal lines between the head and the horn ou 

 the first abdominal segment is the same in the two species, but the space they occupy is wider in 

 S. unicornis, v,'\ii\e the corresponding dorsal lines of the first behind the horn and the second 

 and third segments are firmer, less wavy than in »S'. unicornis. The horn of the first abdominal 

 segment is higher and slenderer, not so thick at the base as in <S'. unicornis, v;\ii\e those on the 

 eighth abdominal segment are much higher and more prominent. The four pairs of dorsal 

 obli(iue lines of »S'. unicornis are less distinct in 8. ijioniea' i\nd more wavy, while the V-shaped 

 dorsal mark just behind them is less sharp and distinct, with more red interlineations in <S'. iponu-a: 



The following description of two larviB found at Brunswick, Me., on the red maple, August 

 14, describes the i)eculiar mimicking coloration better than those hitherto published: 



Full-groicn larra. — Length, 28-33 mm. Wonderfully mimics a dull blood-red portion of a leaf 

 which had been cut partly off and become somewhat twisted, so that the larva itself would easily 

 be mistaken for such a part of a prominent terminal leaf The deception was perfect, as I did 

 not myself at first see it when within ten inches of my eyes, aud on holding it before the eyes of 

 an observing boy of thirteen he could not at first recognize it as a caterj)illar. The same leaf had 

 blotches of dull red, aud the flesh-red abdominal feet of the caterpillar clasped the concolorous 

 red leafstalk. One larva was much deeper blood-red in color than the other, the latter having a 

 more faded tint. 



The head is high and narrow, not so wide as the body, but wider than the fii'st thoracic 

 segment; it is pale livid purplish, darker down the front, with two parallel black-brown lines on 

 each side, bordered with paler, and inclosing a clear pale jiurplish band. The clypeus, labrum, 

 antenna', and region near the eyes are i)ale. A minute piliferous wart on each side of the vertex. 

 The first thoracic segment is mottled with reddish and pale flesh on the sides. A dorsal broad 

 band, divided in the middle by a pale yellow line, beuomes one-half as wide behind ou the second 

 thoracic .segment and passes back to the horn ou the first abdominal segment; the rest of the 

 second and third thoracic segments are pea green, a little paler than the upper side, and darker 

 than the underside of a red-maple leaf, but ou the whole very closely assimilated in tint to the 

 color of the leaf. 



The abdominal segments are in general faded, dull blood-red, due to flue, dark, flesh-red lines 

 and mottlings ou a pale carneous ground. On the first abdomiual segment is a high, nutaut, fleshy, 

 soft, dorsal tubercle which is inclined a little backward, but on being touched bends over down- 

 ward near the l)ack ; the basal half is mottled and lined like the sides of the segment from which 

 it rises, but above becomes bright, clear, blood red, the end being deeply forked, each fork bearing 

 a long black bristle. A median black line passes along the tubercle, becoming forked in front, 

 and behind at the base. Two huge, high, twin, soft tubercles ou the fifth segment are not quite 

 so large as the two similar cues ou the eighth segmeut, but are situated on a much larger humpj 



