MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 7 



and tubercles ;iio wonderfully adiiptod from their resoiiibhince to projections of tln^ leaf on 

 which thov rest or feed, to obliterate the form of tiie eateri)iilai-. 



The larva> lijjured in tiieii- dilferent devt>lopm(>ntal staj^es on Pis. XXI V to XXVIII of my 

 monograph illustrate thi^ tubercles and humps of the fully fed caterpillars, while the figures of 

 the earlier stages show how these ])rocesses gradually develop. A striking case of deception or 

 obliteration, dependent both on form and color, is that of Sc/u':;ur<i ipanuiv^ noted by me on page 

 197 (Pt. I), as follows: 



" Wonderfully mimics a dull blood-red portion of a leaf which had been tait 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 1 did not myself at first see it when 

 within 10 inches of my eyes, and on holding it before the eyes of an observing boy of 13 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 caterpillar clasped the concolorous red leafstalk." 



While near the Profile House, New Hampshire, the last of September, 1 observed the fully 

 grown larva of Sehizura lepttnoides on a maple. At first I entirely mistook it for an upturned 

 tattered sere and brown edge of the leaf, being at first completely deceived, as the outlines and 

 coloration of the creature were exactly like those of the dead and dry portion of the leaf. 



This species, more than any of the others of the genus, as stated in my monograph (p. 2<)1), 

 bears a most striking resemblance to a portion of a dead leaf, '" and several leaves were noticed 

 with portions partly cut off and somewhat curled up, to which the caterpillars bore a striking 

 resemblance, ))oth in shape and color." 



"The apparent aim, or rather the result of the action of the environment, has jjeen to 

 produce a caterpillar who-^e shape and color represent a sere-i)rown more or less twisted portion 

 of a serrated leaf, such as that of a beech, horn})eam, and similar trees." 



The caterpillar of our common S. unicornis, which feeds on the apple, plum, thorn, etc., 

 mimics in shape and color the trees on which it feeds. This has often been noticed. Riley has 

 called attention to this. Miss Emma Payne says that it furnishes a wonderful instance of 

 mimicry. "The green segments just back of the head resemble a small portion of the green 

 leaf, and the other parts admirably counterfeit the brown and russet tints of the dead leaf, while 

 the form of the animal in its various postures aids the deception by its resemblance to a leaf 

 partly alive and partly dead, the green mostlj' eaten and the brown torn." (Amer. Ent., ii, 341.) 

 I have also noticed that this caterpillar feeds in a very conspicuous exposed position, but is 

 "obliterated" or protected "by its resemblance to the twisted, partly dead, ends of some of the 

 leaves, the oblique markings of the larva resembling the twisted dead and russet portions of the 

 leaf." 



Schisura concinna differs from the others of its genus in its stripes and large stout spines. 

 These aid in rendering the creature still more alarming and repulsive to birds and less open to 

 attack from parasitic insects. (See my Monograph, I, p. 215.) 



Period of life when the coloratlonnl features and t\d>ercles of Schlzura appear. — As stated in 

 my monograph (p. 207), the mimetic colorational features, "those which especially enable the 

 larva to escape observation, appear shortly before the creature is half grown, these changes 

 occurring at the end of the third stage, while the movable terrifying tubercle of the first abdominal 

 segment becomes developed at the same time. When feeding on the edge of a leaf, the Schizuraj 

 exactly imitate a portion of the fresh, green serrated edge of a leaf, including a sere-brown 

 withered spot, the angular serrate outline of the l)ack corresponding to the serrate outline of the 

 edge of the leaf. And as the leaves only become spotted with sere-brown markings by the end 

 of summer, so the single-brooded caterpillars do not in the Northern States develop so as to 

 exhibit their protective coloration until late in the sunmier, i. e.. ])v the middle and last of August 

 (p. 207). _ _ . 



Tlie rnarJiings of the species of TIeterocampa. — In my monograph (I, p. 22ti) I have drawn 

 attention to the fact in the case of these beautifully striped and spotted caterpillars, that durino- 

 their ontogeny thei'e is, after the second ecdysis, a strong tendency to a reduction in size of 

 the tubercles, so that by the fourth stage the body becomes smooth and free from all projections 



