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28 MONTHLY NOTES ON GRUBS AND OTHER CANE PESTS. 
in this district, because of a lack of effective protection, and scatter 
before one can get near enough to see what they are eating. By approach- 
ing quietly, however, with the glasses I have been able to observe most 
of our moderate-sized birds feeding upon the beetles. It may be interest- 
ing to note a few of these, such as the magpie lark, yellow-belly, leather- 
head, butcher bird, mynah, satin bower bird, blackbird, laughing jackass, 
&e. The first two are by far the most numerous, and have the advantage 
that they follow their prey to the ground if they fail in their first 
attempt at securing it. 
Most of these birds are too small to swallow the grey-backs at one 
mouthful, but when near enough one ean see that the birds beat the 
insect to pieces on the larger branches before attempting to swallow it. 
Then, too, the quantity eaten by a single bird is limited, but they make 
up for this in numbers. Just after daylight there is a constant stream 
of the birds through the feeding-trees of the beetles. 
As will be noted above, even the fruit-eating birds take kindly to the 
beetles during this, their nesting season, a fact which agrees with my 
experience in America, where most of the seed-eating birds feed their 
young upon insect diet. 
Protection of the bird-life of a country is certainly worth considering, 
for we cannot over-estimate their value to man, even of those birds which 
we sometimes class as enemies, when they occasionally eat our corn or 
kill our chickens. Undoubtedly, birds are:the greatest factor in the 
control of insect pests. 
Theoretically, almost any minute insect, with its rapid methods of 
multiplication, would overrun the earth, making is impossible for man 
or other animals to exist, if the offspring of insects all survived and 
reproduced. 
This has been forcibly illustrated by T. Bainbrigge Fletcher; in his 
work on “‘Some South Indian Insects,’’ where he takes the case of an 
insect laying only two hundred eggs and having a life cycle of one month. 
Starting with lst January for convenience, a single fertilised female 
lays 200 eggs, all of which hatch and mature by the end of the month; 
on the average half of these will be females, each of which will lay 200 
eggs on Ist February, and by the end of February we have 100 « 200 = 
20,000 mature insects, of which half again will be females laying between 
them 10,000 x 200 2,000,000 eggs. Continuing, simple calculation 
shows that by the end of the year the descendants would reach the 
prodigious total of two septillions (2,000,000,000,000,000,000,000,000) 
of individuals. The human mind is quite incapable of grasping the 
significance of such a figure, but a few comparisons may assist the 
imagination. If 1,000 of the insects weighed only 1 oz., their united 
weight would be 558,035,718,571,425-5 tons, and if 1,000 measured 1 eubie 
inch, they would cover an area of almost 50,000,000,000,000 square miles, 
with a uniform. layer 1 inch deep. Taking the dry surface of the whole 
earth to be 51,000,000 of square miles, they would cover the whole of 
this to a depth of over 81 feet. 
