26 
BULLETIN 1393, U. S. DEPARTMENT OF AGRICULTURE 
LENGTH OF LARVAL STAGE 
The length of the larval stage is influenced chiefly by temperature 
and moisture. With a good food supply of normal moisture content 
the larval stage during summer months was found to last from 19 to 
34 days. Individual larvae showed considerable difference in the 
length of the developmental period; thus two larvae completed their 
development during summer in 19 and 34 days, respectively, when 
the mean temperatures ranged from a maximum of 93° F. to a mini- 
mum of 70° F. The longest larval development recorded by the 
writers is 59 days, when the mean temperatures varied from 77° to 
49° F. The development of 44 larvae is recorded in Table 5. In 
Russia Strachov-Koltchin (65) found that the period for larval devel- 
opment varied from 21^ to 84 days, according to the temperature. 
NUMBER AND DURATION OF LARVAL INSTARS 
The larva of the granary 
weevil molts three times at 
more or less regular inter- 
vals. The first three in- 
stars are usually about 
equal in length; the fourth 
is somewhat longer. Dur- 
ing summer weather the 
first three instars are of 
from 4 to 5 dajV duration 
and the fourth lasts from 6 
to 19 days. The duration 
of the larval instars with the 
mean temperature for the 
period is given in Table 5. 
These data indicate that 
the first larval instar was 
from 4 to 12 days in length 
when the temperature 
means were from 84° to 
61° F.; the second instar 
from 4 to 14 days in length 
when the means varied 
from 84° to 59° F.; the third instar from 4 to 17 days in length when 
the mean temperatures for the period varied from 84° to 59° F.; the 
fourth larval stage from 6 to 24 days when the temperature means 
varied from 84° to 59° F. 
Fig. 9.— Chickpeas sectioned to reveal honeycombing of 
interior of seed by feeding of larvae and adults of the 
granary weevil 
THE PUPA 
After attaining its growth the larva prepares a pupal cell at the 
end of its burrow, using a mixture of frass, borings, and larval secre- 
tions to wall in the open end of its burrow. If the cell is accidentally 
broken open before the larva has transformed, the break is repaired. 
After the cell is completed, the larva assumes a prepupal form that 
normally lasts for one day in summer or two days in colder weather 
before it I ransfonns to the pupal stage. Data regarding the length of 
the pupal stage are given in Table 6. 
