66 Journal of Agricultural Research voi. xiii, no. c 



THE EGG 



The egg (PI. 9, B), is scalelike, oval, slightly convex, flattened toward the edge; 

 color grayish white, somewhat iridescent; average measurement 0.59 by 0.72 mm. 

 Central sm^ace finely granulate with reticulating ridges extending from the edge 

 toward, but not to, the center. 



The average incubation periods in 1917 for eggs of the first three 

 generations, respectively, vi^ere 7.5, 4, and 3.1 days. For eggs of the 

 fourth and fifth generations, collectively, the incubation period was 8.3 

 days. 



The progress of development in the egg can be readily observed 

 through its thin shell. In midsummer the progress is so rapid that the 

 embryonic outline is easily discernible 12 hours after deposition. The 

 darkening of the head is first evidenced by the appearance of eyespots. 

 A large majority of the eggs hatch in the late afternoon, during periods 

 when the temperature is high enough to insure steady development. 

 When ready to be hatched the young larva makes rather vigorous move- 

 ments of its head and mandibles against the eggshell, which finally is 

 slit open and the larva walks out. In one instance when the hatching 

 of an egg was closely observed, 57.5 minutes elapsed from the time of 

 the first movement of the mandibles of the larva until it had entirely 

 quitted the eggshell. 



THE LARVA 



The larva (PI. 9, A) is cylindrical; without secondary hair; color varying from 

 white to deep pink, usually more strongly suffused with pink on dorsal side. Legs 

 and prolegs normal. Crochets (31 to 46) uniordinal, in a complete circle. Anal fork 

 developed, yellow to black in color, three to six pointed, prominent. Setal areas 

 broadly chitinized, grayish brown. Thoracic shield light yellow edged with yellowish 

 brown, narrowly divided, moderately broad. Spiracles dark brown or black, small, 

 circular, slightly produced; spiracle on prothorax and that on abdominal segment 8 

 very little larger than those on abdominal segments i to 7. Entire body, except 

 chitinized areas, evenly and finely scobinate; what appears to be a coarse pubescence 

 under low magnification proves, tmder high magnification, to be a mass of short aculei. 



Body setae (PI. 8, D) yellow shading to deep brown, moderately long. Prothorax 

 with la and lb on, and Ic behind the anterior margin of the shield; Ila and puncture 

 y caudad of la; lib directly laterad of Ila; punctiue x dorsad of and approximate to 

 lb, lower than the level of lib; lb, Ic, and lie equidistant; prespiracular shield oval, 

 situated ventro-cephalad of the spiracle, bearing three setae; group VI bisetose. Meso- 

 thorax and metathorax with VI unisetose. Abdominal segments i to 7 with II longer 

 than and ventro-caudad of I; III over the spiracle; Illa approximate to III, dorso- 

 cephalad of the spiracle; IV and V on the same chitinization, under the spiracle, 

 approximate. Abdominal segment 8 with II only slightly below the level of I; 

 III and Ilia cephalad of the spiracle. Abdominal segment 9 with all setae in a line, 

 I and III closely approximate; V, IV, and VI on the same chitinization, approximate; 

 VII unisetose. 



Head light brown, with darker brown mottling; hind margin, ocellar area, and tips 

 of trophi black. 



Head capsule (PI. 8, A, B, C) nearly spherical, slightly flattened, broadly oval in 

 outline viewed from above, a little wider than long; greatest width well behind the 



