22 BULLETIN 427, IT. S. DEPARTMENT OF AGRICULTURE. 
Table 2. — Length of larval stage of potato tuber moth; comparison of larvee reared on 
tubers and larvse reared on potato tops. 
LARV^ REARED ON TUBERS. 
Eggs hatched. 
Nov. 10, 1915. 
July 5,1914.. 
Larval 
stage. 
Days. 
33 
16 
LARVE REARED OX POTATO TOPS. 
Nov. 10, 1915 ! Dec. 7 27 
July 5,1914 July 18 ! 13 
i 
The process of molting is similar to that in other lepidopterous 
larvae, the skin splitting down the dorsum of the first few segments, 
and the larva working its way out through this opening. By far 
the greater time is taken up in preparation for molting and in 
resting after the operation. 
LEAVING THE TUBER. 
When the larvae become mature they usually leave the tuber for 
pupation. If they remain in their channels they come out toward 
the opening, so that the head of the pupa is just under the skin of 
the potato. When the larvae leave the tuber they are very active 
and seldom remain exposed very long. If they are disturbed in any 
way they throw themselves about until they reach shelter of some 
kind. They are especially active when parasites are near, and 
should the latter approach, contort themselves rapidly until the 
parasite has disappeared. 
When a suitable place for pupation is discovered, an operation which 
may consume from an hour to a day, the larva begins a cocoon at 
once, working so rapidly that very soon it is covered with a thin 
mesh. If disturbed, it will often leave its partially completed cocoon 
and seek another place to pupate. Sometimes one larva will interfere 
with another spinning a cocoon to such an extent that the partially 
constructed cocoon will be deserted by both. Parasites, however, 
cause the desertion of the greatest number of cocoons by attempting 
oviposition before the cocoon is completed. 
Cocoons containing pupae of the tuber moth were noted in an old 
bin in the following places: (1) In the eyes of potatoes: (2) between 
potatoes (where they touched or almost touched); (3) between 
potatoes and bin walls; (4) between potatoes and sacks; (5) hi folds of 
sacks; (6) in cracks in bin walls; (7) in nail holes of bin walls; (8) onbin 
walls; (9) in rubbish on floor: (10) on open floor (mostly naked); (11) 
in end of burrow with cocoon partly protruding; (12) hi old burrows 
under dry skin of potatoes. 
