THE SUGAR-CANE MOTH BORER. 29 
emerging at the same time. This overlapping continues until by 
midsummer the broods can not be separated. 
The maximum number of generations may be computed by taking 
the first eggs laid by each generation and assuming that they would 
develop under optimum conditions, thus reaching the adult stage in 
the shortest time possible at the prevailing temperature : 
The first eggs in the spring, laid by adults from the hibernating larvse, 
would hatch by May 1 and the adults appear by June 10. 
Adults of the first generation would lay eggs June 11, and these would 
produce adults on July 24, after 43 days. 
Adults of the second generation would lay eggs on July 25, and these 
would produce adults on September 1, after 38 days. 
Adults of the third generation would lay eggs September 2, and these 
would produce adults on October 8, after 36 days. 
Adults of the fourth generation would lay eggs on October 9, and these 
would produce adults on November 18, after 40 days. 
Adults of the fifth generation would lay eggs on November IS, and the 
larvse would hibernate and emerge in the spring. 
On the other hand, it is equally possible for two generations to 
span the entire year, if we take the last to emerge from hibernation 
and allow them the maximum time for completing their life cycle. 
The latest record of emergence is June 21, 1914, and a moth emerging 
then would not oviposit before June 22 or 23. Eggs laid in the 
insectary June 25, 1914, required 90 days to complete their cycle, the 
adults not emerging until September 23. Larva? hatching the latter 
part of August or in September frequently hibernate, so it is evi- 
dent that the whole year could easily be taken up by two generations. 
These data are based on rearing notes in the insectary and on 
observations in the field. While first-instar larva? have been found 
in the fields from May 5 to the middle of December, and adults 
have emerged in the insectary in December, it is seldom, if ever, that 
the maximum number of generations are produced in the field. Most 
of the larva? reared in the insectary have required from one and a 
half to two or more times the minimum length of time necessary 
to complete their life cycle, and there are usually only four, sel- 
dom five, generations. If the spring is early and other conditions 
favorable, there may be five generations, but if the spring is late 
and cold, as it was in 1915, there will be only four. In the Eio 
Grande Valley there is no true hibernation, although the stages are 
prolonged somewhat in winter, and in Cuba they are more nearly 
the same all the year around. 
POSSIBLE ANNUAL PROGENY OF ONE PAIR. 
It is on account of its rapid rate of reproduction that the borer 
is able to inflict enormous damage. As almost all the larva? are 
killed in the fall by grinding the cane, and as there is a high mor- 
