MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 197 



dash in fronf. hut in the invseiit st.age these dashes are strengthened, united, broader, and 

 coh)red more distiiietly.) 



A noteworthy step taken at this stage is the flnal consoli(hitiou of the two dorsal tuberck'S ot' 

 the first abdominal segment, whicli now l)ecomes a forked siiigk' tuberele. 



Fourth ntdffc, after the third molt. — Observed August 0. Length, 15-1() mm. The characters 

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

 bearing two tubercles. The forked tubercle on the first abdominal 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 nnirbled, except on the pale pea-green meso- and nietathoracic portions, 

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

 entirely changed in shape, being simpk' and pointed like those on the head. 



Fi/tli Kli((jr, after the fourth molt. — Observed August 10-18. Length, L'."i-1'7 mm., and finally 

 35 mm. This stage does not differ essentially from tlie fourth, except that the horns are a little 

 higher. The markings and colors of the mature lar\a seem to be acMjuired in tliis stage. 



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

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

 less angular above and 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 on 

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

 8. unicornis, v,'h[\e the corresponding dorsal lines of the first behind the horn and the second 

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

 segment is higher and slenderer, not so thick at the base as in <S'. unicornis, while those on the 

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

 oblique lines of S. unicornis are less distinct in S. ijiowecr and more wavy, while the V-shaped 

 dorsal mark just behind them is less sharp and distinct, with more red interlineations in S. ipomccv. 



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

 14, describes the peculiar mimicking coloration better than those hitherto publislied: 



FuU-(jrown larra. — Length, I'.S-S.'! mm. Wonderfully mimics a (hill 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, and on holding it befi)re the eyes of 

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

 blotches of dull red, and the flesh-red abdominal feet of the caterjiillar 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 first 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 purj^lish band. The clypeus, labrum, 

 auteiuKe, and region near the eyes are pale. 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 ]iale yellow line, becomes one half as wide behind on the second 

 thoracic segment and passes back to the horn on 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 on 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 fine, dark, flesh-red lines 

 and niottlings on a pale carneous ground. On the first abdominal segment is a high, luitant, fleshy, 

 Soft, dorsal tubercle which is inclined a little backwai'd, but on being touched bends over down- 

 ward near the back; 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 dee|)ly forked, each fork bearing 

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

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

 so large as the two similar ones ou the eighth segment, but are situated on a nuich larger hump; 



