rk of extermination went on. Each female beetle laid on an
average 300 eggs, and each of these eggs hatched into a hungry larva.
Supposing that one-half of these larvae produced female beetles, a simple
calculation will show that in six months a single ladybird became the
ancestor of 75,000,000,000 of other ladybirds, each capable of
destroying very many scale insects.

[Illustration: Twig of olive infected with Black Scale]

Is it any wonder, then, that the fluted scales soon began to disappear?
Is it any wonder that orchard after orchard was entirely freed from the
pest, until now over a large section of the State hardly an Icerya is to
be found? And could a more striking illustration of the value of the
study of insects possibly be instanced? In less than a year from the
time when the first of these hungry Australians was liberated from his
box in Los Angeles the orange trees were once more in bloom and were
resuming their old-time verdure--the Icerya had become practically a
thing of the past.

[Illustration: Rhizobius, the imported enemy of the Black Scale of the
Olive.]

This wonderful success encouraged other efforts in the same direction.
The State of California some years later sent the same entomologist,
Koebele, to Australia to search for some insect enemy of the black
scale, an insect which threatened the destruction of the extensive olive
orchards of California. He found and successfully introduced another
ladybird beetle, known as _Rhizobius ventralis_, a little dark-coloured
creature which has thrived in the California climate, especially near
the seacoast, and in the damp air of those regions has successfully held
the black scale in check. It was found, however, that back from the
seacoast this insect did not seem to thrive with the same vigor, and the
black scale held its own. Then a spirited controversy sprung up among
the olive-growers, those near the seacoast contending that the
_Rhizobius_ was a perfect remedy for the scale, while those inland
insisted that it was worthless. A few years later it was discovered that
this olive enemy in South Europe is killed by a little caterpillar,
which burrows through scale after scale eating out their contents, and
an effort was made to introduce the caterpillar into California, but
these efforts failed. Within the past two years it has been found that a
small parasitic fly exists in South Africa which lays its eggs in the
same black scale, and its grub-like