1 84 



NEEDHAM. 



[VOL. I. 



in 



metamorphosis the wing begins to elongate from its apex and 

 soon crowds downward past the shelf ; and even before the casting 

 of the last larval skin the general form of the adult elytron with 

 the principal furrows upon its surface will have appeared. 1 



The scales of this weevil are wholly developed during the 

 pupal period. They vary in form from simple sensory hairs as 



in the antennal club, and slender, 

 lanceolate, sensory scales in the tarsal 

 brushes, to flat, longitudinally fluted, 

 Lepidopter-like scales of yellow and 

 black colors on the dorsal and more 

 exposed surfaces, and delicate, short- 

 plumose, white, or pale yellow scales on 

 the less exposed surfaces. These, one 

 and all, arise from ordinary, single hy- 

 podermis cells, after the manner of the 

 development of the scales in the lepi- 

 dopterous wings, as described by Mayer 2 

 ct a!. 



First, in early pupal life the cells 

 destined to produce the scales become 

 much larger than their fellows and re- 

 treat a little from the surface, so that 

 their nuclei appear at a lower level than 

 the level of the other nuclei. Then 

 each scale mother-cell loses its attach- 

 ment to the basement membrane, becom- 

 ing rounded off internally and sometimes acquiring a vacuole, and 

 puts forth a process (the scale that is to be) between the adjacent 

 surface cells (cf. Fig. 9). From this process the scale develops, the 

 peculiarities of its own scale kind differentiating rather tardily. 3 



1 There is no need to recount the wing development, since in all important features 

 it is the same in this beetle as in a Coccinellid of which Professor Comstock and 

 I have hitherto published an account (Amer. A r at., vol. xxxiii, pp. 845-858, 1899). 



2 Mayer, A. G., " The Development of the Wing Scales and their Pigment 

 in Butterflies and Moths," Bull. Mus. Comp. Zool. Vol. xxix, pp. 209-236, 

 7 plates, 1896. (Gives bibliography of earlier studies.) 



3 By far the most interesting features of the hypodermis are found in the 

 metamorphosis of the head and the development of the rostrum. These will 



FIG. 3. Vertical section of the fore 

 wing in a grown larva, iv. the 

 wing apex ; c, the loose chitine ; 

 m, muscle ; /, trachea ; f, fat. 



