BIOLOGICAL STUDIES OF THE GREEiSr CLOVER WORM 



13 



October 29. On November 14, however, many of them were observed 

 to be dead on the outer leaves, having been killed by heavy frosts 

 that occurred during the preceding three nights, although a few 

 larvae were still alive in protected places. Subsequently no living 

 larvae were to be found, and their disappearance was attributed to 

 the cold weather. At Nashville, Tenn., eight healthy larvae were 

 placed in the field on an alfalfa plant, under a wire cage, and a 

 thermograph was installed near by. A minimum temperature of 

 34° F. killed three of these larvae the first night. The next night 

 two more succumbed to a temperature of 31° F., but the remaining 

 three survived a temperature of 26° F. and two of them eventually 

 pupated, one later emerging as a moth. 



PREPUPAL STAGE 



When mature, the larva stops feeding, descends to the earth, 

 and on or partly beneath the surface thereof constructs an oval 

 cocoon (fig. 13) of earthen particles or bits of rubbish and leaves 

 loosely webbed together. If no debris be present, plain silken cases 

 are spun, protected on one side by some object. Within the cocoon 

 the larva lies at first in a curved position, which gradually becomes 

 less pronounced as the body contracts. This period lasts from one 

 to six days, with an average of about two days in warm weather. 



PUPAL STAGE 



The pupal stage ordinarily covers a period of from 7 to 24 days, 

 as shown in Table 8, data for which were obtained from 20 pupae 

 reared from May 

 20 to November 

 3. There is evi- 

 dence, however, 

 that this species 

 sometimes hiber- 

 nates as a pupa. 

 From a number 

 of pupae formed 

 between October 

 8 and 19 and ex- 

 posed to outdoor 

 conditions, the 

 moths failed to 

 emerge at the 

 usual time; but 

 when these were 

 brought indoors 

 late in Novem- 

 ber one adult 

 '•merged, having 



Fir;. 13.— Cocoons witli pups of the green clover worm pnrtly out of them 



passed a pupal period of 42 days, and another came out Decem- 

 ber 2 after a pupal period of 44 days. 



