1893.] •'* [Packard. 



RECAPITULATION OF THE MOBE SALIENT ONTOGENETIC FEATURES. 



A. Congenital Adaptational Features. 



1. No tubercles on the prothoracic segment. 



2. The dorsal tubercles on the second and third thoracic and first, 

 fourth, seventh and eighth abdominal segments double the size of those 

 on the other segments, the tubercles being already differentiated at birth. 



3. The prothoracic segment not yet forming a hood, the head not re- 

 tracted within it so readily as in the last stages. 



4. The tubercles each bear only three three-forked glandular setae. 



5. The segments are more distinct than in the later stages. 



6. The body is pearly white, slightly purplish on the back. 



B. Evolution of Adaptational Features. 



1 The body in Stage II assumes nearly the form and colors of the last 

 stage, the tubercles being armed with numerous spines, and some of them 

 tinted with red. 



2. In Stage III, the colors and appearance of the full-fed larva are 

 assumed. 



Larva of Phobetron sp. 



Received from Miss Soule, of Jamaica Plain, Mass., September 10, on 

 maple. Length, 9 mm. Anterior pair of flaps (of which there are ten 

 pairs, five pairs being larger than the others), spreading out on each 

 side, and as broad at the »ud as long ; those of the four other pairs 

 directed backwards ; those of the second pair are one-half as large as the 

 third pair, and are flattened. The fourth pair are very small ; the fifth 

 pair slightly larger than the third. Tlie ninth pair are elongate, conical 

 pointed and pale in hue. The tenth pair are minute, directed horizontally 

 backwards and pale yellow. The upper surface of the body is muclx 

 flattened. The color of the body is pale sandy brown, becoming paler 

 towards the end of the body. Though young it appears to be quite differ- 

 ent from the ordinary larva of P. pithecium. 



The spines and hairs of Pkobetrum pithecium present some interesting 

 peculiarities. Fig. 11, a, represents one of the flaps, which is connected 

 with the body by a very slight attachment at a t, situated at the base of the 

 flattened bilobed process, which is naked beneath ; the free lobe is fringed 

 with delicate plumose hairs ; b, represents the end of one of the smaller 

 flaps, clothed witli plumose hairs and naked at the end, which bears a 

 very long seta ; b', this terminal seta, enlarged still more, with a few thick 

 spinulate setse near the base. 



Fig. 12, two of the plumose hairs from a flap ; all of the other processes 

 have similar hairs. 



The last genus of the spinose Cochliopodids is Isa (Sisyrosea). Fig. 13 

 represents the end of one of the lateral tubercles of the first abdominal seg- 



PROC. AMER. PHILOS. SOC. XXXI. 140. M. PRINTED APRIL 12, 1893. 



