THE GRANARY WEEVIL 31 
It has been found that of adults held at 85° F. under starvation 
conditions 50 per cent may die by the end of the first week, with a 
certain few surviving for 19 days. Others, kept at 55° F., were 
very sluggish; 50 per cent survived for about 3 weeks, and one for 
65 days. When given food, adult life is much longer and averaged 
between 7 and 8 months. Numerous adults lived well over 1 year 
and of certain adults subjected to a temperature ranging between 
50 Q and 60 Q F., a few lived for 2 years and 5 months. 
Adults begin ovipositing during summer as early as six days after 
emergence. In early spring the preoviposition period is about three 
weeks. Adults that emerge late in the fall have the longest preovi- 
position period, since they hibernate and do not begin ovipositing 
until the following spring. The extremes found in the preoviposition 
period were 6 and 148 days. 
The granary weevil lays from one to five eggs per day when ovi- 
position occurs, although one or two eggs per day is the more usual 
number. There is, however, considerable variation, as between dif- 
ferent females, in the number of eggs laid per day under identical 
temperature conditions. This same variation extends to the dura- 
tion of oviposition and to the total number of eggs laid by females. 
The longest oviposition period recorded was 287 days, from August 
27 to June 10 of the year following. The shortest oviposition period 
was 67 days, from March 19 to May 25. The average length of the 
oviposition period for adults emerging during spring and early sum- 
mer is between three and four months. The total egg-laying ca- 
pacity of single females varied from 36 to 254. 
The incubation period varied in length from 4 days at a mean 
temperature of 78° to 80° F. to 15 days at a mean of 61° F. No 
eggs were observed to hatch after the temperature of the grain had 
reached 95° F. or above, or when it had fallen to 50° to 55° F. 
Since adults do not oviposit until the temperature is from 61° to 
63° F., and do not oviposit with regularity until a temperature of 
66° to 68° F. is reached, there seems little reason to believe that eggs 
are ever laid when they can not hatch within 15 days, unless it be 
in late fall on approach of cold weather, when they will fail to hatch 
and will die. 
The larva must have for food seeds in size sufficient to supply 
its growth requirements. In its growth it molts three times at more 
or less regular intervals. Where development proceeded fairly rapidly 
the duration of the four larval instars was found to be as follows 
when the mean temperature varied from 59° to 84° F.: First instar, 
4 to 12 days; second instar, 4 to 14 days; third instar, 4 to 17 days; 
fourth instar, 6 to 24 days. With a good supply of normal moisture 
content the larva? completed their development in from 19 to 34 days 
during summer weather when the mean temperature ranged from a 
maximum of 93° F. to a minimum of 70° F. The longest larval 
development recorded by the writers is 59 days when the mean tem- 
peratures varied between 77° and 49° F. 
After attaining its growth the larva prepares a pupal cell, and 
after from one to two days in the prepupal form it transforms to 
the pupa. During the hottest summer weather, when the mean tem- 
peratures vary from a maximum of 85° to 95° F. to a minimum of 
61° to 71° F., the pupal stage lasts from 5 to 7 days (mean tem- 
peratures for the period varying from 68° to 82° F.). During colder 
weather, with a mean temperature for the period of development 
