RATE OF INCREASE OF GIPSY MOTH. 
Ill 
in successive years, the unhatehed or latest clusters being easily distinguished from 
the hatched or "old" clusters, and the age of these latter, whether one. two, three, 
or more years, being indicated by their state of preservation. The ratio of the aver- 
age annual increase of 10 such colonies was found to be 6.42; that is, six or seven 
egg clusters on an average may be found in the second season to one of the first 
season . 
If the number of eggs deposited by the average female moth be 
set at 500, and if the sexes of her progeny are equally divided, a 
potential increase of 250-fold for each annual generation is provided 
for. Under complete control only one pair of moths would average 
to be produced from each mass of eggs deposited, and since each egg 
represents an individual embryo, all but 2 of each 500 must fail to 
reach full maturity. Reduced to percentage this is equivalent to 
the survival of 0.4 per cent and the destruction of 99.6 per cent of 
the gipsy moths in one stage or another every year. Since the total 
number of gipsy moths in any locality can not possibly be computed, 
the only method by which mortality through any cause may be 
expressed is on this basis. 
It will surprise many who have not given the matter considera- 
tion to learn what an extraordinary ajijKirtnt mortality it requires to 
offset a potential increase of 250-fold. The gipsy-moth caterpillars 
molt live or six times after t hey batch and before they change to pupa?, 
making the number of caterpillar stages >ix or seven. If through 
natural controlling agencies 50 per cent of the young caterpillars 
were destroyed in the iirst stage before they had molted, and this 
was followed by similar destruction of another 50 per cent in the 
second stage, and so on through the third, fourth, fifth, sixth, and 
seventh stages, respectively, and in addition 25 percent of the pupa? 
and 25 per cent of the adults before depositing their eggs were simi- 
larly destroyed, it would still permit of a slight annual increase. 
The following table (if the incongruity of fractions as applied to 
insects may be overlooked) indicates the number of survivors of each 
stage resulting from the hatching of a mass of 500 eggs: 
Stage. 
Number. 
Ix>ss. 
Number 
remain- 
ing. 
Potential increase. 
Eggs 
500 
500 
250 
125 
62 
31 
15.5 
7.75 
3.875 
2. 906 
/'< r ct lit. 

50 
50 
50 
50 
50 
50 
50 
25 
25 
500 
250 
125 
62 
31 
15.5 
7.75 
3. 875 
2. 906 
2. 179 
250 fold. 
125 fold. 
62 fold. 
31 fold. 
15.5 fold. 
7.75 fold. 
3.875 fold. 
2.906 fold. 
2.179 fold. 
1.634 fold. 
Caterpillars 
First 
Do 
Second 
Do 
Third 
Do 
Fourth 
Do 
Fifth 
Do 
Sixth 
Do 
Seventh 
PupfT 
Adults 
To give another illustration: The life of the gipsy-moth caterpillar 
is approximately seven weeks. If beginning on the first day after 
