Packard.] 
INSECTS OE THE GAKDEN. 
35 
have made out microscopically, are probably all or nearly all 
fecundated. We have, then, for every two individuals which 
have appeared this year, a deposit of five hundred embryos 
for the generation to appear seventeen years hence. 
Now, from what has just been stated about the uniformity 
of their numbers, each time, it appears that from the liabili¬ 
ties of destruction during the long term of seventeen years, 
out of these five hundred embryos, only two appear certain 
of life and appearance in their perfect state, that is, just re¬ 
placing'the two parents. The chances of life therefore with 
this insect, are, in round numbers, two in five hundred. This 
calculation may seem strange to some, but if we reflect, it 
can scarcely be otherwise ; for suppose the chances were 
double, that is, four in five hundred, then we should have at 
each time just double the numbers of their last time, which 
observation has shown to be untrue and which would augur 
much evil for the future condition of the vegetable world in 
the localities of their appearance. Even if their chances 
were three in five hundred, or half again the original stock, 
agriculturists would quickly perceive the difference. 
To sum up the matter, then, we have here an insect whose 
economy and conditions of life are so unique that it is almost 
entirely isolated from human destructive agencies and which 
is obliged to deposit five hundred chances for the certainty 
of securing two. The ovaries have been formed with this 
capacity and- the whole internal economy is of a correspond¬ 
ing character.” 
The shrill noise made by the male Cicada, “for,” says 
Anacreon, “they all have voiceless wives,” originates in two 
kettle-drum-like organs situated under the wings at the base 
of the hind body. 
The Aphis (Fig. 24).—We should not be doing justice to 
the subject of garden pests if we omitted a special notice of 
that wonderful creature, the Aphis or Plant Louse. The 
first to appear in spring as the buds unfold, the .very last to 
