I Have Never Seen An Orifice,
And It Is Scarcely Possible That The Tree Can Yield So Much.
A Similar
But much smaller homopterous insect, of the family `Cercopidae',
is known in England as the frog-hopper (`Aphrophora spumaria'),
when
Full grown and furnished with wings, but while still in the pupa state
it is called "Cuckoo-spit", from the mass of froth in which
it envelops itself. The circulation of sap in plants in our climate,
especially of the graminaceae, is not quick enough to yield much moisture.
The African species is five or six times the size of the English.
In the case of branches of the fig-tree, the point the insects congregate on
is soon marked by a number of incipient roots, such as are thrown out when
a cutting is inserted in the ground for the purpose of starting another tree.
I believe that both the English and African insects belong to the same family,
and differ only in size, and that the chief part of the moisture
is derived from the atmosphere. I leave it for naturalists to explain
how these little creatures distill both by night and day as much water
as they please, and are more independent than her majesty's steam-ships,
with their apparatus for condensing steam; for, without coal,
their abundant supplies of sea-water are of no avail. I tried
the following experiment: Finding a colony of these insects busily distilling
on a branch of the `Ricinus communis', or castor-oil plant,
I denuded about 20 inches of the bark on the tree side of the insects,
and scraped away the inner bark, so as to destroy all the ascending vessels.
I also cut a hole in the side of the branch, reaching to the middle,
and then cut out the pith and internal vessels. The distillation
was then going on at the rate of one drop each 67 seconds,
or about 2 ounces 5-1/2 drams in 24 hours. Next morning the distillation,
so far from being affected by the attempt to stop the supplies,
supposing they had come up through the branch from the tree,
was increased to a drop every 5 seconds, or 12 drops per minute,
making 1 pint (16 ounces) in every 24 hours. I then cut the branch
so much that, during the day, it broke; but they still went on
at the rate of a drop every 5 seconds, while another colony
on a branch of the same tree gave a drop every 17 seconds only,
or at the rate of about 10 ounces 4-4/5 drams in 24 hours.
I finally cut off the branch; but this was too much for their patience,
for they immediately decamped, as insects will do from either a dead branch
or a dead animal, which Indian hunters soon know, when they sit down
on a recently-killed bear. The presence of greater moisture in the air
increased the power of these distillers: the period of greatest activity
was in the morning, when the air and every thing else was charged with dew.
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