24 
BULLETIN 1428, U. S. DEPARTMENT OF AGRICULTURE 
and kind of food, the time of year in which the young larva hatches, 
and the prevailing temperatures. 
The effect of the food supply on the duration of the larval growth 
has been discussed in a preceding paragraph. It was found that 
Avhen the larva is reared on certain foods such as corn, wheat, Graham 
flour, etc., growth is rapid and, other conditions being favorable, the 
larval stage is short, whereas if the larva is fed upon less nourishing 
foods, growth is correspondingly slower and the larval stage may be 
considerably prolonged. 
Of several hundred cadelles hatched at different times of the 
year and supplied with an abundance of suitable food a great many 
completed their growth and transformed within 3. months, a majority 
within 7 months, and all within 14 months after hatching. (Table 
5.) Of a large group fed upon refined white flour none succeeded in 
transforming, although certain of them lived to be about 2 years old. 
The time of the year when the young larva hatches apparently 
has some bearing on the duration of the larval stage aside from the 
influence to be expected from changing climatic conditions. Of the 
larva? that hatch in the late spring and early summer months, al- 
though rearing conditions may be to all appearances identical, a 
certain percentage have a short larval life and transform the same 
year, as indicated by the data of Table 7, whereas the rest have a long 
larval life and do not transform until the following spring or sum- 
mer, as indicated by the data of Table 8. The rearing records of 
the several hundred cadelles mentioned in the preceding paragraph 
show that all larva? that hatched in March and April completed their 
growth and transformed the same year; 90 per cent of those hatch- 
ing in May transformed that year, 40 per cent of those hatching in 
June, 10 per cent of those hatching in July, but none of those hatch- 
ing in August transformed the same year. Table 4 contains the data 
just mentioned and also gives the minimum, maximum, and average 
lengths of the larval stage for the larva 1 that hatch during the dif- 
ferent months of the active breeding season. It is interesting to 
note at this time that of the specimens reared those having the 
shortest larval life and those having the longest larval life all hatched 
in June of the same year and were reared under identical conditions. 
Table 4. — Influence of time of hatching upon length of larval stage of the cadelle 
Month in which larva hatched 
Number 
of 
larvae 
Trans- 
forming 
same 
year 
Length of larval stage 
Minimum 
Maximum 
Average 
25 
15 
51 
59 
47 
26 
Per cent 
100 
100 
90 
40 
10 

Days 
93 
80 
60 
48 
62 
233 
Days 
138 
104 
376 
414 
346 
318 
Days 
100 
April 
89 
102 
209 
July 
270 
August 
272 
Temperature naturally has a marked effect upon the duration of 
the larval stage but its effect is often modified or vitiated by the 
nature of the food and time of hatching of the larva. As a gen- 
eral rule, the larval stage becomes shorter as the seasonal tempera- 
ture increases. Table 5 contains data showing the variation in the 
