INSECTS INJURIOUS TO POTATO, ETC. 



225 



United States, injury to potato is nearly confined to California, 

 although tobacco is attacked in the South where the insect is 

 known as the tobacco leaf-miner or split-worm. It is probable 

 that this insect may in time become a pest in other regions, 

 though not in the colder temperature States. 



The moth (fig. 144) resembles a clothes-moth, but is darker. 

 The wing expanse varies from ^ to about % of an inch. The 

 fore-wings are mottled with dark 

 brown and black, and the hind- 

 wings are narrow, with long 

 fringes. Eggs are deposited on 

 the leaves, and the minute worms 

 (&, c) hatching from them bur- 

 row into the stems and afterward 

 into the potato tubers. Fre- 

 quently early injury is done to 

 plants in the field, but as the 

 larvae grow they work, later in 

 the season, farther into the stems, 

 and when these 

 their way to the tubers and finish 



<ssmmmm» 



harden make Fig. 144— Potato tuber worm, ff. Moth; 

 b, c, larva or "worm" ; d, pupa; e. /, 

 abdominal segments of larva, a-d, 

 their growth there. The potato Three times natural size: e, /, more 



is subject to infestation through- l""'^',^"^- <'"^^=^ ^'f^' "• ^ Dept. 



•• ^ Agr.) 



out the year, provided the tubers 



are stored in places that are not too cold for the insect's devel- 

 opment. The life cycle, according to the studies of Mr. W. T. 

 Clarke, may be accomplished in nine weeks, and in the winter, in 

 the mild climate of California, this period is sometimes run in 

 twelve weeks. When the larva is about six weeks of age it 

 comes to the surface and transforms to pupa at the mouth of 

 its burrow, or seeks a crack or depression in the potato when 

 the tubers are stored. The usual course of the tuber worm is to 

 mine beneath the outer skin of the plant, and molds and rots 

 (bacterial and fungous growths) follow in its wake, the stalk 



