THE SUGAR-CANE MOTH BORER. 
23 
ing. Three or four larvae often are found living in the same stalk 
of cane, but in these cases they are more or less separated by their 
burrows, and it is not likely that large larvae are eaten by others 
under field conditions, where they have freedom of action, whereas 
the habit of small larvae of congregating in the terminal buds of the 
plants is very conducive to cannibalism, and many doubtless are 
destroyed by their companions. 
GKOWTH. 
The rate of growth is dependent upon many external conditions, 
the temperature and kind of food being the most important factors, 
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Fig. 7. — Diagram showing relationship of mean temperature to larval growth of the 
sugar-cane moth borer per day in hundredths of millimeters, showing line of maxi- 
mum growth of normal individuals. The dots represent growth of individuals in 
hundredths of millimeters. 
but larvae feeding under similar conditions show a great variation 
in the rate of development and in the length of the larval period, as 
is shown by figure 7. Under favorable conditions the rate of in- 
crease in body length is about 0.75 mm. per day, but it is often much 
less. Larvae are from 1.5 to 2 mm. long when hatched and from 25 
to 30 mm. long when fully grown. 
MOLTS. 
Before molting the larvae stop feeding for a few hours or some- 
times longer and appear stiff and helpless. The skin then ruptures 
