The sense of direction—How locusts look flying—Follow no
leader—Unanimity of movement—Flight by moonlight—Roosting at
night—Extirpated in Cyprus—The “Chinese Wall” system—Not
adapted to Australia—Deference to aboriginal feeling—Locusts
in Australia—Strange ceremony of egg-laying—Inadequate
explanation.
IN regard to the faculty of direction with which locusts seem endowed,
Dr. Munro says: “The flying locusts in the Argentine come from a
northerly direction, and the hoppers or creepers march towards the
south, although it might be, so far as abundance of suitable food goes,
to their manifest advantage to go in an opposite direction. In certain
countries the direction may be known. In this country (South Africa) it
will be found that they march towards the south, and not towards the
north, east, or west, though either of these directions might have been
better for them. The direction may not be true south; it may incline at
one time to the south-east, at another to the south-west; but, taken as
a whole, it will be southwards.” And he adds: “If proof be needed that
the ‘_saltonas_,’ another name—perhaps the Portuguese one—for these
wingless armies, march in one direction, it is abundantly found in the
experience of the screen and trap, or Cypriote system of destroying
locusts, which is based on this fact, and on this alone. This is
conclusive demonstration.”[21]
The distance that these footgangers—to translate, almost without
changing, the Dutch word—go in a day depends upon the amount of food
they find upon the road, but fluctuates, as a rule, between one mile and
two. They start about eight o’clock, when the sun begins to get hot; and
halt for the night a little before the sun sets. Dr. Munro describes the
way in which the female locust, before laying her eggs, drills a hole in
the hard ground with the disc-like extremity of her abdomen, but he
mentions nothing very peculiar in connection with the laying of the eggs
such as characterises the performance of that ceremony by the Australian
plague locust, as will be mentioned shortly.
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[Illustration: A PLAGUE OF LOCUSTS]
The dark cloud is entirely composed of locusts, which
sometimes fill the air from twenty feet to two or three
thousand feet above the ground. The poor people attempt in
vain, by shouts, by lighting fires, and waving branches, to
avert the attack.
The first appearance of these locusts is in enormous hosts, which may
sometimes be seen at a distance of from seven to ten miles, and then
appear as a black cloud in the clear and rarefied air of South Africa.
“It is impossible,” says Dr. Munro, “to estimate the number of locusts
in these clouds, but some idea may be formed from the fact that when
they are driven, as sometimes is the case in a storm, into the sea, so
many are washed ashore that they lie on the beach as a bank from three
to four feet thick and from fifty to one hundred miles in length, and
the stench from the corruption of their bodies, it is affirmed, is
sensibly perceived for a hundred and fifty miles inland.”[22] The aerial
movements of the locusts, when they fairly surround one, are described
as “curious, interesting, and pretty.” Distant vision (more especially
overhead) is impeded on account of their numbers. The effect when you
look on them in the sun’s rays resembles “snow falling thickly and
gently,” and the sun is only seen as though it were in eclipse. “Its
light is darkened and shadows cannot then be cast from it.”[23] The
height at which the swarm flies may be anything between forty feet and
two miles from the ground, but as a rule it is not greater than 400
feet, though from 500 to 800 is not uncommon. Sometimes they fly by
moonlight, but this is not their usual practice. As in their earlier
wingless state, they seem to act by one common impulse, which prevents
confusion. It is obvious, indeed, that with such myriads filling the
whole air, a leader could neither be perceived nor followed, and from my
own observations I am convinced that the same difficulty applies to this
way of explaining the movements of flocks of birds. I have never,
myself, seen any evidence of birds being led by one or more of their
number, but much to convince me that when banded together, in numbers,
their movements are governed by a totally different principle, viz. that
of thought transference or thought-unity—collective thinking, as I have
elsewhere called it—for that is what it most suggests. If this is not
the case with locusts, what, I would ask, is the alternative
explanation? If great hosts of men be neither led nor of one mind where
to go, they must fall into confusion, impeding one another’s movements,
and this is a law which has to do with numbers merely, without respect
to the species of which they are composed. It has often been noticed,
however, that large crowds seem liable to be swayed suddenly by some
common impulse.
Locusts may fly about a district all day doing but little harm, “and at
sundown,” says Dr. Munro, “the sight becomes interesting beyond
description, for the whole company then appear to vie with one another
in order to roost quickly.”[23] When all have found a resting-place,
“every twig, branch, bush, or separate stalk of the corn or wheat or
flax are completely covered, and sometimes they stick to each
other”[23]—three or four deep even. “As far as the eye can see, the
surface assumes a brownish-red hue. Pillars, posts, or the walls of
houses are all alike to them at the time of roosting for the night.”[23]
Such, then, is the Plague Locust of South Africa, which is, when at
maturity, about three inches long. Some years ago, however—the exact
date is not given—a larger and handsomer species made its appearance,
and is thus referred to in a letter which was sent by “A Disgusted
Farmer” of Grahamstown to one of the South African papers: “The new red
locust, which, during the last month, has spread from the Orange River
to the sea, coming apparently from the north as well as from Natal, is
doing terrible damage. Everywhere fruit-trees are being
destroyed—quince, apricot, fig, orange, lemon, naartje trees. Not only
are the leaves eaten, but young branches are all barked, so that they
are probably killed. A splendid crop of mealies, covering the whole of
Peddie, Lower Albany, Alexandria, and other districts, has been entirely
destroyed. Pumpkin plants are being eaten too. Vegetables of all
kinds—lucerne, cattle-cabbage, and kale—are also swept away. The locusts
are laying everywhere, and, no doubt, the plague will continue some
years. What is the agricultural farmer to do?”[23] I do not know, but
here, probably, were there locusts, he would pick out all such birds as
fed on them and try to get them taken off the list of protected species,
shooting them illegally all the while he was petitioning.
Dr. Munro’s work was published in 1900, and its principal object was to
induce the South African Government to adopt the system of dealing with
the locust plague which had been practised with such entire success in
the isle of Cyprus. Whether this has since been done, and with what
results, I am unable to say. In Cyprus, however, the locusts, which from
the year 1600, especially, have changed the country from a garden into a
wilderness, were in one season almost entirely swept away. The method by
which so great a result was effected is the invention of an Italian
gentleman—Signor Matthei by name—resident in the island, and is based
upon the inability of the immature locusts, the footgangers—probably the
grown ones too, but this is immaterial—to crawl up a smooth
perpendicular, still more an overhanging surface. Such a surface was
supplied by a long band of leather, glazed and polished, surmounting a
strip of calico, which was made about four feet high, but need not, as
it was afterwards found, have been more than two. This insurmountable
obstacle, supported at intervals by sticks set in the ground—not
upright, but slanting a little towards the path of the locusts—was set
up over a large area of country like a miniature Chinese Wall, and
proved even more insurmountable. At intervals along the inner side of
the barrier deep pits were dug, whilst at wider ones stood men provided
with brooms, spades, brushwood, and all else requisite. When the locusts
arrived at the Chinese Wall they climbed up the canvas part of it, but
being unable to pass the smooth band of leather they fell down in heaps,
and their ever-increasing multitudes soon filled the pits, in which they
were buried, burnt, stamped down, or otherwise provided for. Afterwards
their carcases were dug out and heaped on carts, and the pits, being
empty again, were ready for more. In this way two hundred million
quadrillion billions—or something of that sort—of locusts were
destroyed, and next year when everything was again ready for them hardly
any appeared. By this invention, as simple as it is ingenious and
inexpensive, the locust plague in Cyprus has become a thing of the past,
and if the conferrer of so great a benefit was ever not a man of large
fortune, let us hope that that has become a thing of the past, too, for
he must have saved several to the British Government. If the locusts,
after coming to the Chinese Wall and finding themselves unable to climb
it, had turned round and walked in another direction, this would have
made a capital instance of intelligence shown by insects—but they did
not do so.
With native labour, the above system, which has been so entirely
successful in Cyprus, could, Dr. Munro makes no doubt, be put in
operation in Africa; but Mr. W. W. Froggatt, the Government entomologist
of Australia, does not think it adapted for that country. Writing in
_The Agricultural Gazette_ of New South Wales (March, 1901), Mr.
Froggatt says, “Though they have been successfully dealt with in Cyprus,
Egypt, Algeria, and India by means of trenches, traps, and burning in
the hopper state, and digging up and destroying the eggs in the earlier
stage, in nearly all cases the areas infested were comparatively small;
the labour employed was so cheap that small armies of natives could be
employed at a small cost to destroy them, while in several instances an
autocratic government made the natives, whether they were inclined or
not, work at their plan of destruction.” In Australia, where, “whether
they were inclined or not,” the natives have been got rid of, very much
as though they were locusts—or some less stubborn insects—themselves,
this would not do.
It was in the summer of 1899 that Mr. Froggatt, in consequence of
reports received of the advent of locusts in various parts of the
country, left Sydney for Condobolin. On the way there many “mobs”—to use
the Australian word—were encountered, and numbers of locusts flew in at
the railway carriage windows. Upon alighting, Mr. Froggatt became the
witness of a very interesting spectacle—a ceremony, as it may well be
called, in which vast numbers of the insects were engaged—of which he
gives the following description:—
“In the open red soil we found them laying their eggs in thousands, and
the operation was very remarkable. The female set to work by pressing
the tip of her abdomen into the soil, and working the plates at the
apex, so that she gradually bored a regular circular shaft, slightly
over an inch in depth and under a quarter of an inch in diameter, the
segments of the abdomen extending and stretching as the work progressed.
But the most extraordinary part of the operation was that each female,
while boring the chamber to deposit the eggs, was attended by two males,
each of which rested his head against hers, with his antennas resting
over her head, and the inner foreleg clasped over the prothorax behind
the base of the head. Resting like this, with the tails of the two
attendant males pointing outwards, the three formed a three-rayed star.
Wherever the business of egg-laying was going on, each female and her
attendants were surrounded by a cluster of admiring males, averaging
from thirty to fifty in number, generally in bunches of fours or fives,
forming an irregular ring round them, but separated from her by a clear
space of three or four inches. In no instance were there ever more than
two males touching the female, though we examined thousands of them at
work.”[24]
What is the meaning of this odd performance?—this ceremony, as it
appears to me, though Mr. Froggatt takes a utilitarian view of it. “The
probable and only reason,” he remarks, “that I can see for the
attendance of the two males upon the egg-laying female is that it
enables her to get a firmer grip of the ground, and, in fact, holds her
in position till she completes her task.”[24] But why, then, should the
females of no other species of locust, as far as we are aware, require
this aid, and should not the soil of Africa be as hard as that of
Australia? “I can find,” says Mr. Froggatt, “no record of this habit in
any of our described species, which have the same habits.”[24] Again,
besides the two chief actors, we have the admiring ring of from thirty
to fifty males, who can be of no possible service, but whose conduct
shows that they take a strong interest in what the female is doing. What
is it, too, that regulates the number, or, at any rate, the personality
of the assistant males? If it is a matter of rendering assistance only,
and the two males who do so are bound to the female by no more special
tie than the crowd of interested spectators, why do not these, or some
of them, push forward? Why is there never any contention between them?
These considerations make me think that there is something of a formal
and ceremonious character about these queer proceedings, and that they
are governed by the same general law as are certain antics or set
figures amongst birds, wherein three individuals take a part. What one
requires to know is the courting and marital relations of the male and
female locust before the egg-laying takes place.
These little locusts—_Epacromia terminalis_ is the specific name—are
only about an inch in length, and the male, from the description, seems
a little brighter than the female, which may be due to sexual selection.
The female appears to lay nineteen eggs only, neither more nor less,
which is not so many as one would have expected from the Arabian legend.
With some other species, however, the number more conforms to the
statement said to have been made to Mahomet.
There is no vanity at all in my thinking that this has been an
interesting account of locusts, since I myself have had nothing to do
with it. In giving a general description, from general reading, of
things generally known, and that have been described scores of times
before, one is entitled to use one’s own language, and to think,
perhaps, that one stands at no particular disadvantage in doing so. But
when, in regard to something specially curious or interesting, the
graphic words of an eye-witness are before one, the best thing one can
do, in my opinion, is to copy them out. If it be suggested that this is
but a lazy way of writing a book, my reply is that a compiler best shows
his industry in the searching out of material. The late Professor
Romanes was alive to this fact, and has left us in consequence his
_Animal Intelligence_—one of the most interesting books that exist, in
my opinion—about one-eighth of which, or perhaps a little more, is
written by himself.
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Footnote 21:
Dr. Æneas Munro, The Locust Plague and its Suppression.
Footnote 22:
The Agricultural Gazette of New South Wales, March, 1900.
Footnote 23:
Dr. Æneas Munro, The Locust Plague and its Suppression.
Footnote 24:
The Agricultural Gazette of New South Wales, March, 1900.
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