86 PROCEEDINGS OP THE AMERICAN ACADEMY 



One of this brood began to spin, and had completed the exterior of 

 its cocoon by August 1. 



The object of the purplish edging on the suranal plate and anal legs 

 was impressed upon me while observing a large full-fed caterpillar 

 resting by a short leafstalk, the leaf having been broken off so as to 

 be a quarter of an inch long and curved. In color and shape it ex- 

 actly resembled the purplish edgings of the suranal plate and legs, and 

 thus added to the protective resemblance to a leaf and its stalk. 



A fine large T. polyphemus was observed at Providence, September 

 27, on the chestnut. I was struck with the resemblance of the outline 

 of the creature's back — the segments being angular so as to render 

 the body serrate, each tooth-like form of the segment surmounted by 

 a tubercle and long hair — to the serrated edge of the leaf, each of 

 the teeth ending in a long hair. It is not improbable that the ances- 

 tors of Telea, Actias, and others with angular segments, may originally 

 have fed on trees with such serrated leaves, and that later they adopted 

 as their more usual food-plant such trees as the oak, in which the 

 edges of the leaves are either smooth or simply lobed. 



Recapitulation of the more Salient Ontogenetic Features. 



A. Congenital Features. 



1. The setae (bristles) of Stage I. but little longer than the tubercles, 



and both truncate and distinctly bulbous at tip. 



2. A slight but distinct differentiation in size and color of the dorsal 



tubercles, those of the 3d thoracic and 9th abdominal segments 

 being of the same size, and larger than those on uromeres 1-7, 

 and of a deeper yellow shade. (Stage I.) 



3. The homologue of the " caudal horn " is distinctly double, and 



more deeply divided than in any other American genera of 

 Attacinfe ; each fork about as long as thick. (Stage I.) 



4. Abdominal legs each with twenty-four crotchets (a larger number 



by 6 to 8 than in the other genera), Stage I. 



5. Each abdominal segment (uromere) with a lateral pair of trans- 



verse black slashes in Stage I. 



6. The two tubercles in Stage I. on the suranal plate slender, papilli- 



form, and approximate. 



B. Evolution of later Adaptational Characters. 



1. The lateral pair of black transverse stripes on each uromere nearly 



or quite disappear in Stage II. 



2. The segments more convex and angular in Stage III. 



