18 



BULLETI]Sr 427, U. S. DEPARTMENT OF AGEICULTUEE, 



are, naturally, all degrees between these extremes. There seems 

 to be no true hibernation of the egg, those which develop slowly- 

 passing through about the same color changes and requiring about 

 the same time in proportion as those which develop very quickly. 



There is more or less regularity in hatching of the eggs deposited, 

 even where the period of incubation is the longest. In the case of 



those which took 34 

 days, all which were 



deposited during one 

 night hatched during 

 36 hours. Practi- 

 cally all the unin j ured 

 eggs hatch success- 

 fully. From a count 

 kept of those depos- 

 ited under laboratory 

 conditions only 5 out 

 of 730 eggs failed to 

 hatch ; of these 4 were 

 sterile, and the other, 

 after partial develop- 

 ment, collapsed. 



The sheUs of the 

 eggs, as indicated by 

 the color changes be- 

 fore hatching, are 

 very thin and collapse 

 shortly after the lar- 

 vae leave them. 



THE LARVA. 



EMERGENCE AND FEEDING 

 HABITS. 



The larva emerges 

 by eating a hole- 

 through the eggshell. 

 The newly hatched 

 larva is about 1 milli- 

 meter in length and 



is quite light in color with the exception of the head, which is dark 



brown; it is inconspicuous and very difficult to detect when on the 



surface of a potato. 



The larvae are quite active and begin feeding almost at once. They 



seldom move far from where they hatch before they begin to burrow. 



When the egg is laid on a leaf there is shght chance that the larva 



Fig. 15.— Potato tuber-moth injiiry to exterior of fruit of eggplant. 

 (Original.) 



