24 



BULLETIN 427, U. S. DEPAETMENT OF AGEICULTUEE, 



pupa must continue all the time, though, of course, at a greatly 

 reduced rate. For this reason this longer pupal stage must be 

 classed as retarded development and could hardly be termed true 

 hibernation. 



THE ADULT. 



EMERGENCE. 



The skin of the pupa splits along the dorsum of the thorax, and the 

 moth by contracting itself draws its head from the pupal case. From 

 this time on it is never quiet, contracting and expanding its abdomen 

 and withdrawing its legs from their cases on the venter of the pupa. 

 When the legs are free and the body has started to move in the case, 

 the whole insect is free within a few moments. The freshly emerged 

 adult generally moves very little until it has expanded its wings to 

 their normal size. Sometimes the latter process is quite slow, but 

 generally within a short time the wings reach beyond the tip of the 

 abdomen. Even after development is apparently complete the 

 moth prefers not to attempt flight for some time, but if disturbed 

 either feigns death or seeks a place of concealment with a character- 

 istic jerky runniag movement. 



For some tune after emergence the adult spends most of the time 

 in hiding, but if sweetened water is placed near it the insect will feed 

 readily. 



HABITS OF THE MOTH. 



Under field conditions the habits of the insect are well adapted to 

 protect it until the eggs are deposited. During the day the adult 

 hides beneath rubbish, or if the fields are clean, under clods of earth. 

 Its coloring is very protective, and it is difficult to locate the adults 

 even after they have been observed to alight. They seldom fly in 

 the field during the brighter hours of midday, unless disturbed, and 

 then the flight is short and jerky, and on alighting they seek con- 

 cealment. When they fly to the potato vines they hide beneath the 

 leaves, so that they are seen with difficulty. Under field conditions 

 they have not been noted to take food. The activity increases with 

 the temperature, being greatest during warm nights. 



PROPORTION OF THE SEXES. 



The proportion of the sexes during the year remains very nearly 

 constant and almost equal. Pupse selected at random at various 

 times of the year gave the results shown in Table 3. 



Table 3. — Proportion of sexes of the potato tuber moth. 



Month. 



January 

 April . .". 



July 



October 



Number 

 of pupse. 



127 

 200 

 200 

 100 



Male. 



69 

 111 

 95 

 52 



Female. 



104 

 43 



Not 

 emerging. 



