67 
Table XXII. — Rate of groivth of larvx at different temperatures. 
Location. 
Average 
tempera- 
ture. 
Larval 
stage. 
Sums of ef- 
fective tem- 
peratures. 
Incubator 
° F. 
85.4 
71 
57 
Days. 
14 
2.8 
a 41 
° F. 
425 
Luboratorv 
677 
o516 
« Three molts. 
The effect of severe cold on larvse was also tried in a number of 
cases. All subjected to temperatures somewhat below freezing were 
killed outright by an exposure of from twenty-four to forty-eight 
hours, but of those kept at 34° F. for forty-eight hours a small per- 
centage survived and matured successfully. 
The ability to live for any length of time without food is not very 
great. Newly hatched larviB live about twenty-four hours in the 
laborator3% ])ut it is probaVjle that in nature the drying effect of the 
sun and other untoward conditions would shorten this period consid- 
erabl} . Larger larvae usually live several days, and occasionally 
three-fourths or nearly grown ones will pupate successfully if deprived 
of food. 
NUMBER OF MOLTS. 
The number of molts has already been stated. Of 100 larvae reared 
in the laboratory at Paris, Tex., in 1904, 90 per cent molted 5 times, 
8 per cent 4 times, and 2 per cent 6 and 7 times, respectively. . 
The cause of this variation in the number of molts in regard to the 
10 per cent thus varying could always be traced to abnormal condi- 
tions. Highly nutritious food and excessive care in breeding appar- 
ently caused less than the normal number of molts. Seven out of 
eight larvae reared on cowpeas molted thus. Molts in excess of the 
normal were paused by neglect and insufficient or disagreeable food. 
PROCESS OP MOLTING. 
The process of molting is normal. A fews hours after ecdysis the 
larva stops feeding and remains in an extended, slightl}^ arched posi- 
tion. In this condition it is very helpless, especially when nearly full 
grown. At the time of molting the body contracts spasmodically, the 
skin splits back of the head, and the head is thrust out. Three or four 
minutes more pass before the larva has shed the skin entirely, and 
after three or four hours feeding begins again. 
In midsummer the stages preparatory to molting are very short (15 
to 18 hours), and in the fall longer (3 to 4 days). After the earlier 
molts the larva? sometimes devour their own shed skins, as do also the 
older ones, but more rarely. 
