450 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 7 



Fig. 28 — Diagramatic curve illustrating the seasonal gradations of temperature at 

 Batesburg, S. C, and the approximate zone of mid-summer aestivation (shaded) 



like organ (mandible) which may be extruded or retracted at pleasure. 

 This structure is swung, like a mower's scythe, backward and forward 

 with an arching sweep of the oral region of the larva. This rasping 

 organ becomes vestigial in the pupa, but still remains visible as a 

 black, anterio-median ventral prominence (see plate 14, fig. 3 a). 



The cephalo-pharyngeal skeleton (of which the rasping organ is 

 a part) is Y-shaped in outline and consists of the usual three closely 

 articulated sclerites. The base of the Y (the middle on hypostomal 

 sclerite) is directed forward and is extended terminally into a some- 

 what semicircular plate (plate 14, fig. 4 a). This plate, the distal 

 sclerite, bears on its outer surface five or more sharp recurved teeth. 

 The hook-bearing plate lies normally exposed outside the mouth. 

 The arms of the organ are of unequal size. The upper arm (plate 14, 

 fig. 4 c) is much longer and broader than the lower and is somewhat 

 geniculate; the lower arm (plate 14, fig. 4 b) is short, straight and nar- 

 row. The entire device is densely chitinized, the rasping, hook- 

 bearing sclerite being especially opaque. A thin hyaline border 

 occurs on the inner face of the inferior lateral plate. No parastomal 

 sclerites occur in this species, but the hj^postomal segment bears 

 a heavily chitinized ridge or process which in position and appearance 

 is at least analogous, if not homologous, to a weakly fused parastomal. 



The pivotal center of the device appears to lie at some point along 

 the hypostomal segment. Muscle bands extend from the distal 

 ends of the Y-arms to the cuticular integument, and it is obviously the 

 alternate contraction of these muscles which imparts action to the 

 external plate. 



Leaves frequently harbor several individuals and as many as a 

 dozen well-formed mines have been counted in a single cotton leaf. 



