THE GRAPE-LEAF SKELETON IZER. 



81 



mm. .and the minimum 0.31 H mm. Tlic snci'ni'c siz(> of i]\o o<r,a' is 

 0.r>()() mm. by O.^UD mm. 



The eggs are deposited on liic underside of the k'uves in clusters, 

 and from 12 clusters counted, 

 the minimum contained 7 eggs, 

 the mnxinnun 2()0, the average 

 cluster containing 107.9 eggs. 

 Observations on l,0;)r) eggs 

 gave the average length for 

 the Q<x<i: stage as 7.92 days, 

 with a maxinnini of 9 days 

 and a mininnim of 7 days, the 

 average mean temperature for 

 the i)eriod of incubation of the 

 various eggs being 77.5° F., 

 with cloudy weather ])revail- 

 ing. The eggs under observa- 

 tion were from the second 

 generation of motlis, and the 

 length of the stage would ])robably be somewhat greater for the first 

 generation on account of lower temi)erature. 



Fig. 1.1. — The grapo-leaf skeletonizcr {Tlarri- 

 xiiiti (imcrirunu) : a. Ess, sroatly onlarfred ; 

 h, cluster of eggs in natural position on 

 l.'af. (Original.) 



LARVA. 



Fii'.'^t histar. — Body yellowish-white, translucent. Head similar in 

 color to body, retractile, broader than body, which gradually tapers. 

 Segments 2-13 with a transverse median row^ of spinelike bristles, 

 about 0.2 mm. in lengih, extending to venter on each side; whitish 

 when viewed under a f-incli objective, but the dark-colored joints 

 cause them to appear blackish under a small magnification. Thoracic 

 feet small, pointed, color similar to body ; abdominal feet small, 

 visible only as small wartlike protuberances. Length, 1-1.25 nun.; 

 width of head, 0.18-0.25 nun. (variable). 



Second instar. — Body dilute-yellow, head retractile, darker, eyes 

 and mandibles dark brown. Tubercular areas now distinct under a 

 f-inch objective as a transverse row of wartlike clusters of whitish, 

 segmented bristles about 0.2 mm. in length, with apex, joints, and 

 bulb at base of the bristles black. All the segments laterally, and 

 dorsum of the anterior and posterior segments with long, whitish, 

 segmented hairs about 0.75 mm. in length. Thoracic feet small, 

 pointed, dilute-brownish; abdominal feet, more distinct now, appear- 

 ing as small stumplike projections. Length, l.()(>G-2 muL ; width of 

 head, 0.283-0.333 mm. 



Third instar. — Body orange-yellow, head retractile, dilute-brown, 

 eyes and mandibles brownish-black. Segments 2-13 .show wartlike 



