Social Life in the Insect World | Page 9

by the disposal of more debris. Thus we
are caught in a vicious circle. The mere packing of the powdered earth
rejected behind the excavator would not account for so large a void.
The Cigale must have a special method of disposing of the waste earth.
Let us see if we can discover the secret.
Let us examine a larva at the moment of emerging from the soil. It is
almost always more or less smeared with mud, sometimes dried,
sometimes moist. The implements of excavation, the claws of the
fore-feet, have their points covered by little globules of mortar; the
others bear leggings of mud; the back is spotted with clay. One is
reminded of a scavenger who has been scooping up mud all day. This
condition is the more striking in that the insect comes from an
absolutely dry soil. We should expect to see it dusty; we find it muddy.
One more step, and the problem of the well is solved. I exhume a larva
which is working at its gallery of exit. Chance postpones this piece of
luck, which I cannot expect to achieve at once, since nothing on the
surface guides my search. But at last I am rewarded, and the larva is
just beginning its excavation. An inch of tunnel, free of all waste or
rubbish, and at the bottom the chamber, the place of rest; so far has the
work proceeded. And the worker--in what condition is it? Let us see.
The larva is much paler in colour than those which I have caught as
they emerged. The large eyes in particular are whitish, cloudy, blurred,
and apparently blind. What would be the use of sight underground? The
eyes of the larvæ leaving their burrows are black and shining, and
evidently capable of sight. When it issues into the sunlight the future
Cigale must find, often at some distance from its burrow, a suitable
twig from which to hang during its metamorphosis, so that sight is
obviously of the greatest utility. The maturity of the eyes, attained
during the time of preparation before deliverance, proves that the larva,
far from boring its tunnel in haste, has spent a long time labouring at it.
What else do we notice? The blind, pale larva is far more voluminous
than in the mature state; it is swollen with liquid as though it had
dropsy. Taken in the fingers, a limpid serum oozes from the hinder part
of the body, which moistens the whole surface. Is this fluid, evacuated

by the intestine, a product of urinary secretion--simply the contents of a
stomach nourished entirely upon sap? I will not attempt to decide, but
for convenience will content myself with calling it urine.
Well, this fountain of urine is the key to the enigma. As it digs and
advances the larva waters the powdery debris and converts it into a
paste, which is immediately applied to the walls by the pressure of the
abdomen. Aridity is followed by plasticity. The mud thus obtained
penetrates the interstices of the rough soil; the more liquid portion
enters the substance of the soil by infiltration; the remainder becomes
tightly packed and fills up the inequalities of the walls. Thus the insect
obtains an empty tunnel, with no loose waste, as all the loosened soil is
utilised on the spot, converted into a mortar which is more compact and
homogeneous than the soil through which the shaft is driven.
Thus the larva works in the midst of a coating of mud, which is the
cause of its dirtiness, so astonishing when we see it issue from an
excessively dry soil. The perfect insect, although henceforth liberated
from the work of a sapper and miner, does not entirely abandon the use
of urine as a weapon, employing it as a means of defence. Too closely
observed it throws a jet of liquid upon the importunate enemy and flies
away. In both its forms the Cigale, in spite of its dry temperament, is a
famous irrigator.
Dropsical as it is, the larva cannot contain sufficient liquid to moisten
and convert into easily compressible mud the long column of earth
which must be removed from the burrow. The reservoir becomes
exhausted, and the provision must be renewed. Where, and how? I
think I can answer the question.
The few burrows uncovered along their entirety, with the meticulous
care such a task demands, have revealed at the bottom, encrusted in the
wall of the terminal chamber, a living root, sometimes of the thickness
of a pencil, sometimes no bigger than a straw. The visible portion of
this root is only a fraction of an inch in length; the rest is hidden by the
surrounding earth. Is the presence of this source of sap fortuitous? Or is
it