SAP-SUCKERS
“What do plant-lice eat?” asked Jules one day. “I have never seen them
feeding on leaves.”
“They do not feed on them,” his uncle replied; “they drink the sap
through a very fine, short, pointed sucker which they carry against the
breast when not in use. The insect plunges it into the plant and for
whole days without moving drinks the sap at the point pricked. When
this place is sucked dry it passes to another, but without much change
of position. The plant-louse is a sedentary creature; to move around a
stem no bigger than your little finger is for the louse a long journey
fraught with perils not lightly to be faced, a few steps forward to
make room in the rear for some fifty children as fast as they are
brought into the world being about all that the boldest of these
creatures dares to undertake. But plant-lice of the last generation of
the year have wings and lay eggs which in the spring renew the race
annihilated by the cold of winter. These winged lice are no timid
stay-at-homes like the others: they gladly quit the natal leaf to see a
bit of the world. It is their business to travel hither and yon and lay
their eggs in many places so that in the following spring all plants
shall have their share of lice, and it is to fulfill this duty that
they are expressly provided with wings. Clouds of these traveling
plant-lice, dense enough to obscure the light of day, have been
observed.
“Many other insects have, like the plant-louse, a straight, pointed
sucker which they plunge into the substance they wish to drain of its
juice, and which they hold against the breast when not in use. The
cicada furnishes us a very good example, as do also the large bugs
found on trees and on many plants. The cabbage feeds two of them: the
harlequin cabbage-bug, which is red with numerous black spots, and
still another cabbage-bug of a bluish-green color with white or red
spots.
“Bugs of this class have four wings, the upper pair covering the other
pair when in repose. The forward half of each upper wing is hard like
the beetle’s wing sheaths, but the other half is membranous and of fine
texture. This structure makes them half sheaths for protection and half
wings for flying, and it is because of this peculiarity that insects of
this sort are called hemiptera, or half-winged creatures. The cicada is
a half-winged insect, as is also the plant-louse, although its upper
wings (I am speaking of winged plant-lice, of course), instead of being
one half hard and the other half of a more delicate texture, have the
same fineness and transparency throughout. But the most striking
characteristic of these insects, and the one that determines their mode
of life, is the beak for sucking. So we will call hemiptera all insects
equipped with a pointed sucker which lies against the breast when in
repose, and we will not concern ourselves with the question of wings,
whether half or entirely membranous.”
“Do the hemiptera form an order by themselves?” asked Jules.
“They form an order in the same way that coleoptera, lepidoptera,
hymenoptera, diptera, and so on, form each an order. But hemiptera do
not undergo so thorough a transformation as other insects, being born
with very nearly the form they will always have. The chief change
consists in the growing of wings, which the insect does not have at
first, but acquires later when it has attained sufficient size. In some
species several generations succeed one another before the winged
state, which is the perfect one, is reached. Plant-lice belong to this
class, the earlier generations of the year having no wings, and only
the last being equipped with them.
“A hemipterous insect with habits somewhat like those of the plant
louse causes considerable damage to pear-trees. It is commonly called
the flea-louse of the pear, and is a small reddish insect with
diaphanous wings that fold at an angle like the two sides of an
acute-angled roof. It is found on pear-trees, and more rarely on
apple-trees, toward the end of April. The eggs are laid one by one in
slight gashes made in the leafstem by the female with a little auger
situated at the end of the abdomen. The larvæ that come from these eggs
grow rapidly and differ from the perfect insect only in their lack of
wings. By sloughing the skin these larvæ become nymphs, short and
stubby and already having on each side a rudimentary wing. In its final
form the insect acquires perfect wings. In all three of its successive
stages the insect plunges its sucker into the tender bark, or into the
leaves, and sucks the sap. The best way to destroy these creatures is
to use a hard bristle brush on those parts of the bark where they are
to be found in multitudes.”