240 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Two young willi horns exacitly ii.s in I'l. XXXII, liys. li, 'la, were found on the maple August 

 20-29; one of them uiolteil August 27, and then a])i)eared as in PI. XXXII, figs. .S, ;5rT. Wheu first 

 found they were stretched out motionless along the midrib on the underside of the leaf. 



In the last stage the larva differs from that of //. (/itttiritfa in having the three pairs of 

 lateral sere brown patches, the difterence being simjtiy colorational rather than as regards the 

 armature. 



The htHt stage. — Length, 30 mm. The head is still high, bilobed, narrowing toward the vertex, 

 with two black lines in front extending from each side of the clypeus and ending on the vertex 

 near the tubercles, and another behind one on each side extending from the antenna' and 

 mandibles back halfway up the back side of the head. 



The antlers of the early stage are now replaced by two high, conical, rounded, polished knobs, 

 each bearing a minute bristle, and from them on the inside two parallel lines extend backward. 



The anal legs are shorter than in the early stage, being about as long as the well-rounded 

 supraanal plate. Doubleday probably gives the characteristic attitude of this caterjiillar wheu 

 not walking, its legs being moderately elevated. 



I add a fuller description of this larva when fully grown. 



Mature larva. — Length, 3.") mm. Head high, narrowing from below to the vertex, which is 

 very slightly bilobed. Two black lines ascend from the antenn;e and approach each other on the 

 vertex, the space between the lines slightly roseate; outside the head is light uniform brown with 

 a slight greenish and lilac tinge; the clypeus is small, while the median suture of the ejiicranium 

 in front is very distinct. On the prothoracic segment behind the vertex are two contiguous, thick, 

 conspicuous, large, conical, bright red tubercles, dark at the tip; there are no other humps, and 

 none at the end of the body, which is thickest at and a little behind the middle, the body tapering 

 gradually to tlie long aiuil legs, which fork widely and are longer than the others, but are constantly 

 used. Supraanal plate unusually small. Color of a peculiar brownish green dotte<l with black 

 points and specks, with a white spot between the prothoracic tubercles. Body above finely 

 marbled with dark brown, with a broken, pale, flesh-colored line, beginning on the mesothoracic 

 segment, and on the first to third abdominal segments suddenly expanding into a large, broad, 

 sublozenge shaped spot, suddenly succeeded, over the segment bearing the first pair of abdominal 

 legs, by a rounded spot. On the top of the fifth segment begins another dorsal patch of the 

 same color, which widens and extends down the sides of the third segment from the end. Along 

 the middle of this patch are two parallel dark lines; and two broader dark lines of speckles begin 

 on the fourth segment from the end of the body, converging and uniting on the second segment 

 from the end, forming on the last two segments a broad median dorsal line. Thoracic legs reddish; 

 abdominal legs reddish flesh t^olor. Anal legs slender, reddish. On the oak at Providence, 

 October 9. 



'J'o recapitulate: 



1. The pair of prothoracic antlers of the early stage of this larva, and those of f/iittiritta 

 obliqiia and umbrata, is certainly the most unique and unexpected feature to be found among 

 liCpidopterous larvre, and the object evidently is to render the creature frightlul to its assailants. 



2. The rest of the body is without large horns and markings, the latter of which api)ear in the 

 later stages and are such as to comi)letcly adapt it to a maple leaf late in summer or in the autumn 

 when portions begin to wither and to turn brown. Hence the horns, if present, would then only 

 serve to attract attention to it, and thus they are modified into much less prominent tubercles. It 

 should be observed that in the full grown larva of IT. astartr, which has the same general colors and 

 markings as H. guttivitta and JI. bitiudata, and is thus protected, the prothoracic tubercles are 

 absent. 



How to account for the ai)i)earance of such enormous horns may be impossible even after we 

 have become accpxaiiited with the early stages of all the allied species, though it should be borne 

 in mind that the young of Citheronia regalis and Eacles inqjerialis, as well as Anisota, have nearly 

 as large spines when first hatched. 



rupa.— Body plump; of the sauie shape as in IT. gxlitivUta. Head full and rounded, with the 

 two parallel ridges between the eyes slightly larger and more prominent than in 11. guttivitta 



