mimetic resemblances among spiders. They mimic ants much oftener than
other creatures, and ants are very abundant, are specially protected,
and are much more numerous than the mimetic spiders. To the first
law, also, they conform to a great extent, since everything tends to
show that in tropical America and in Africa the ant and the spider,
the one mimicked and the other mimicking, are always found together.
So far as I can discover, however, the ant-like spiders of North
America are not found in company with any species of ant which they
resemble. This may be because they do not mimic any particular
species, but only the general ant-like form; or, considering that the
genera which contain their nearest relatives are much more abundant in
Central and South America, it may be that these forms were originally
tropical, mimicking some tropical species of ants, and that after the
Glacial Epoch they migrated northward, leaving the ants behind them.
However this may be, their peculiar form has served them well, since
they have maintained themselves as fairly abundant species with a
lower fecundity than is found in any other group of spiders.
The cases in which one species mimics another may be divided,
according to the kind of benefit derived, into four classes: Class 1.
As a rule, where we find one species mimicking another, the mimicked
species possesses some special means of defence against the enemies of
both. This defence may consist of a disagreeable taste or odor, as in
the Heliconidae, which are mimicked by other butterflies; of some
special weapon of offence, as where wasps and bees are mimicked by
flies and moths, or poisonous vipers by harmless caterpillars; or of a
hard shell, as where the coriaceous beetles are mimicked by those that
are soft-bodied.
Instances of this rule are exceedingly numerous; indeed, Wallace says
that specially protected forms are always mimicked; still we have
nothing mimicking our Gasteracanthidae.
Class 2. The mimetic may prey upon the mimicked species, its disguise
enabling it to gain a near approach to its victims; as the mantis,
mentioned by Bates as exactly resembling the white ants upon which it
feeds; and the flies which mimic bees, upon which they are parasitic,
and are thus able to enter the nests of the bees and lay eggs on the
larvae.
Class 3. The mimetic species may, by its imitation, be protected from
the attacks of the creature it mimics, as is the case with the
crickets and grasshoppers which mimic their deadly foe, the hunter
wasp.
Class 4. The mimetic species may prey upon some creature which is
found commonly with, and is not eaten by, the mimicked species.
No two of these classes are mutually destructive so that in any case
of mimicry a double advantage may be gained.
Let us see which of these advantages has directed the development of
mimetic tendencies among spiders.
While among beetles and butterflies we most commonly find mimicry of
one species by another within the same order, we have no instance of a
spider mimicking another spider. This may be accounted for by the fact
that the specially protected spiders depend for their safety upon the
possession of hard plates and spinous processes, and although the
hardened epidermis might be imitated (we know that hard-shelled
beetles are mimicked by others that are soft), spines could scarcely
be imitated by a soft-bodied creature with sufficient accuracy to
insure disguise.
While spiders most commonly mimic ants, we hear also of their
imitating beetles, snail-shells, ichneumons and horseflies. There is
also a curious Madagascar species which looks exactly like a little
scorpion, the resemblance being heightened by its habit of curving its
flexible tail up over its back when irritated.
Those that resemble beetles comprise nearly all the species of the
genera Coccorchestes and Homalattus. These are small spiders with
short, convex bodies. The abdomen fits closely over the cephalothorax,
and the epidermis, which has usually a metallic lustre, is sometimes
coriaceous. Striking examples are found in H. coccinelloides, which
bears a strong resemblance to beetles of the family Coccinelloidae, and
in C. cupreus, in which certain marks on the abdomen imitate the
elytra of beetles.
The following account of a spider which mimics a snail-shell is given
by Mr. G. F. Atkinson;--
"An undescribed species of _Cyrtarachne_ mimics a snail-shell, the
inhabitant of which, during the summer and fall, is very abundant on
the leaves of plants in this place. In the species of Cyrtarachne the
abdomen partly covers the cephalothorax, is very broad at the base, in
this species broader than the length of the spider, and rounds off at
the apex. When it rests upon the under side of a leaf with its legs
retracted it strongly resembles one of these snail-shells by the color
and shape of its abdomen. The two specimens which I collected deceived
me at first, but a few threads of silk led me to make the examination.
The spider seemed so confident of its protection that it would not
move when I jarred the plant, striking it several hard blows. I
pulled the spider forcibly from the leaf, and it did not exhibit any
signs of movement until transferred to the cyanide bottle." ...
Trimen gives an account of the imitation, by spiders, of horseflies, a
case falling into Class 2, as follows:--
"Hunting spiders are in some cases very like their prey, as may
everywhere be noticed in the case of the species of Salticus which
catch horseflies on sunny walls and fences. The likeness is not in
itself more than a general one of size, form and coloring; but its
effect is greatly aided by the actions of the spider, which walks
hurriedly for short distances, stopping abruptly, and rapidly moving
its falces, in evident mimicry of the well-known movements so
characteristic of flies."
Instances of spiders mimicking ants are very numerous, and in many
cases the resemblance is so close as to, at first sight, deceive a
trained naturalist. This resemblance is brought about by the spider's
body being elongated and strongly constricted, so that it appears to
be composed of three segments instead of two, by the color, by the way
in which the spider moves about, zig-zagging from side to side like an
ant, and by its habit of holding up one pair of its legs and moving
them in such a way that they look exactly like the antennae of an ant.
Ants may be regarded as specially protected, by their sharp, acid
flavor, and in some species by the possession of stings or of horny
processes.
On the ground that there are birds which do eat ants, and eat them
greedily, it has been thought by some naturalists that they cannot be
considered specially protected creatures, and that, as spiders can
therefore derive no protection from mimicking them, all cases of such
mimicry depend upon the spider's increased ability to capture the ants
as prey, but I am convinced that this is too hasty a conclusion. It is
unquestionably true that some birds feed almost exclusively upon ants,
but these are the exceptions. It is a common thing to find that
specially protected groups, which are safe from the attacks of most
creatures, have their special enemies. Thus, even the nauseous
Heliconidae are preyed upon by certain spiders and wasps; and bees, in
spite of their stings, are preferred to other insects by the
bee-eaters. Moreover, the ant-devouring birds are found largely among
the wood-peckers, which eat the ants that run on the trunks of trees,
and are therefore not a source of danger to the ant-like spiders, the
American species of which, so far as I can learn, live entirely upon
the ground.
In the United States comparatively small numbers of either ants or
spiders are eaten by birds, but in tropical America there are enormous
numbers of humming-birds feeding almost exclusively upon spiders, and
there the protective advantage of looking like ants must be of great
importance to the smaller species.
Belt considers that the advantages gained by ant-mimicking Central
American spiders lies entirely on the side of protection. In relation
to this subject he says: "Ant-like spiders have been noticed
throughout tropical America and also in Africa. The use that the
deceptive resemblance is to them has been explained to be the facility
it affords them for approaching ants on which they prey. I am
convinced that this explanation is incorrect, so far as the Central
American species are concerned. Ants, and especially the stinging
species are, so far as my experience goes, not preyed upon by any
other insects. No disguise need be adopted to approach them, as they
are so bold that they are more likely to attack a spider than a spider
them. Neither have they wings to escape by flying, and generally go in
large bodies easily found and approached. The use is, I doubt not, the
protection the disguise affords against small insectivorous birds. I
have found the crops of some humming-birds full of small, soft-bodied
spiders, and many other birds feed on them. Stinging-ants, like bees
and wasps, are closely resembled by a host of other insects; indeed,
whenever I found any insect provided with special means of defence I
looked for imitative forms, and was never disappointed in finding
them."
The ant-like species are probably protected by their appearance from
the attacks of many of the larger spiders. We have kept great numbers
of Attidae in captivity, and, although they devoured flies, gnats,
larvae, and other spiders, they would never touch ants. Among spiders,
however, as among birds, we find that certain groups subsist almost
entirely upon ants.
The class of spiders whose mimicry protects them from their enemies,
whether they are birds or other spiders, probably includes at least
two of our own ant-like species, Synageles picata and Synemosyna
formica, which, in confinement, are always hungry for gnats, but will
not touch ants, even of small size.
The existence of a class of spiders which mimic the particular species
of ants upon which they prey is not to be questioned, but it is
doubtful whether the benefit to the spider is increased facility in
capturing the ant, or whether it is merely protective. It may be that
the spider, by virtue of its resemblance to the ant, not only gets an
abundant supply of food, but also escapes being eaten itself, and thus
enjoys a double advantage. Both Bates and Wallace take the ground that
the advantage derived by the spider consists in greater ease in the
capture of prey, but both of these writers refer to spiders only
incidentally to illustrate a general proposition, without special
consideration of their peculiar conditions.
Mr. Herbert Smith, who has paid a good deal of attention to this
subject, is inclined to believe that the mimicry in question is
entirely protective. He writes as follows:--
"In the United States there are a few rare spiders that mimic ants.
Here at Taperinha we find a good score of species of these spiders
aping the various kinds of ants very closely; even the odd, spiny
wood-ant, _cryptocerus_, furnishes a pattern, and there are spiders
that mimic the wingless ichneumons. We find, after a while, that the
spiders prey upon ants just as our spiders catch flies; indeed, this
fact has already been noted by other observers. But we go a step
beyond the books when we discover not only that the spiders eat the
ants, but that they eat the particular ants which they mimic. At all
events, we verify this fact in a great number of cases, and we never
find the spiders eating any but the mimicked species.... I do not like
to hazard a theory on this case of mimicry. It is difficult to suppose
that the quick-witted ants would be deceived even by so close a
resemblance; and, in any case, it would seem that the spiders do not
require such a disguise in order to capture slow-moving ants. Most
birds will not eat ants; it seems likely, therefore, that this is
simply another example of protection; the spider deceives its enemies,
not its prey; it mimics the particular species that it feeds on,
because it is seen in that company when it is hunting, and among a
host of similar forms is likely to pass unnoticed."
At first sight, and especially in view of the fact that such cases are
not uncommon among insects, it would be naturally supposed that the
object of the mimicry was to enable the spider to approach its victim
without exciting suspicion; and it is difficult to account, on any
other supposition, for the very close resemblance between certain
species of spiders and the particular species of ants which they prey
upon. It seems as though the highest point of _protective_ benefit
would have been reached long before the resemblance of the spider to
the ant had become so close as it really is. On the other hand, it is
difficult to believe that ants are deceived, even by those spiders
which mimic them most closely, when we remember that their perceptions
are so keen that they discriminate not only between ants of their own
and different species, but even between ants of their own species
living in two different communities.
The mimicry of ichneumon flies by spiders was noted some years ago by
Mr. Herbert Smith. This case comes under Class 3, in which one species
mimics another which preys upon it. Great destruction is caused by
ichneumons which lay their eggs on the bodies of the live spiders,
and the disguise probably protects the spider by leading the fly to
mistake it for one of its own species.
We have no proof that spiders ever mimic ants as a method of escaping
from them, but it is possible that this sometimes happens. We know
that some ants prey upon them. The foraging ants of South America
destroy spiders as well as many kinds of insects, and Wallace mentions
a small, wood-boring ant which fills its nest with small spiders.
If the spiders that feed upon ants deceive them by their mimicry those
which are preyed upon by ants would gain an advantage by a similar
disguise. I once placed a little ant-like spider of the genus
Herpyllus in a bottle with three ants no larger than itself, which I
had caught with it in the sweep-net. In a very few minutes the ants
had killed and begun to devour the spider. It may be that the
resemblance was sufficiently close to deceive them in the open, but
failed when spider and ants were confined together in close quarters.
THE BATH OF THE BIRDS
BY RICHARD JEFFERIES.
[Illustration]
One morning Sir Bevis went down to the brook. Standing on the brink,
he said: "Brook, Brook! what are you singing? You promised to tell me
what you were saying."
The brook did not answer, but went on singing. Bevis listened a
minute, and then he picked a willow leaf and threw it into the bubbles
and watched it go whirling round and round in the eddies and back up
under the fall, where it dived down and presently came up again, and
the stream took it and carried it away past the flags. "Brook, Brook!"
said Bevis, stamping his foot; "tell me what you are singing."
And the brook, having now finished that part of his song, said:
"Bevis, dear; sit down in the shadow of the willow, for it is very hot
to-day, and the reapers are at work; sit down under the willow and I
will tell you as much as I can remember."
"But the reed said you could not remember anything," said Bevis,
leaning back against the willow.
"The reed did not tell you the truth, dear; indeed, he does not know
all; the fact is, the reeds are so fond of talking that I scarcely
ever answer them now or they would keep on all day long, and I should
never hear the sound of my own voice, which I like best. So I do not
encourage them, and that is why the reeds think I do not recollect."
"And what is that you sing about?" said Bevis impatiently.
"My darling," said the brook, "I do not know myself always what I am
singing about. I am so happy I sing, sing, and never think about what
it means; it does not matter what you mean as long as you sing.
Sometimes I sing about the sun, who loves me dearly, and tries all day
to get at me through the leaves and the green flags that hide me; he
sparkles on me everywhere he can, and does not like me to be in the
shadow. Sometimes I sing to the wind, who loves me next most dearly,
and will come to me everywhere in places where the sun cannot get. He
plays with me whenever he can, and strokes me softly and tells me the
things he has heard in the woods and on the hills, and sends down the
leaves to float along; for he knows I like something to carry. Fling
me in some leaves, Bevis, dear.
"Sometimes I sing to the earth and the grass; they are fond of me,
too, and listen the best of all. I sing loudest at night to the stars;
for they are so far away they would not otherwise hear me."
"But what do you say?" said Bevis; but the brook was too occupied now
to heed him and went on.
"Sometimes I sing to the trees; they, too, are fond of me and come as
near as they can; they would all come down close to me if they could.
They love me like the rest, because I am so happy and never cease my
chanting. If I am broken to pieces against a stone, I do not mind in
the least; I laugh just the same and even louder. When I come over the
hatch, I dash myself to fragments; and sometimes a rainbow comes and
stays a little while with me. The trees drink me, and the grass drinks
me; the birds come down and drink me; they splash me and are happy.
The fishes swim about, and some of them hide in deep corners. Round
the bend I go; and the osiers say they never have enough of me. The
long grass waves and welcomes me; the moor-hens float with me; the
kingfisher is always with me somewhere, and sits on the bough to see
his ruddy breast in the water. And you come too, Bevis, now and then
to listen to me; and it is all because I am so happy."
"Why are you so happy?" said Bevis.
"I do not know," said the brook. "Perhaps it is because all I think of
is this minute; I do not know anything about the minute just gone by,
and I do not care one bit about the minute that is just coming; all I
care about is this minute, this very minute now. Fling me in some more
leaves, Bevis. Why do you go about asking questions, dear? Why don't
you sing and do nothing else?"
"Oh, but I want to know all about everything," said Bevis. "Where did
you come from, and where are you going, and why don't you go on and
let the ground be dry--why don't you run on, and run all away? why are
you always here?"
The brook laughed and said: "My dear, I do not know where I came from,
and I do not care at all where I am going. What does it matter, my
love? All I know is I shall come back again; yes, I shall come back
again." The brook sang very low and rather sadly now: "I shall go into
the sea and shall be lost; and even you would not know me; ask your
father, love; he has sailed over the sea in ships that come to
Southampton, and I was close to him, but he did not know me. But by
and by, when I am in the sea, the sun will lift me up, and the clouds
will float along--look towards the hills, Bevis, dear, every morning
and you will see the clouds coming and bringing me with them; and the
rain and the dew, and sometimes the thunder and the lightning, will
put me down again; and I shall run along here and sing to you, my
sweet, if you will come and listen. Fling in some little twigs, my
dear, and some bits of bark from the tree."
"That I will," said Bevis; and he picked up a stone and flung it into
the water with such a splash that the kingfisher flew away; but the
brook only laughed and told him to throw another and to make haste and
grow bigger and jump over him.
"S--s, we shall meet by the drinking place," said the grasshopper; and
was just hopping off, when Bevis asked him what the birds went down to
bathe for.
"I'm sure I do not know," said the grasshopper, speaking fast, for he
was rather in a hurry to be gone; he never could stand still long
together. "All I can tell you is, that on Midsummer Day every one of
the birds has to go down to the brook and walk in and bathe; and it
has been the law for so many, many years that no one can remember when
it began. They like it very much, because they can show off their
fine feathers which are just now in full color; and if you like to go
with me, you will be sure to enjoy it."
"So I will," said Bevis; and he followed the grasshopper, who hopped
so far at every step that he had to walk fast to keep up with him.
They went on in silence a good way, except that the grasshopper cried
"S--s" to his friends in the grass as he passed, and said good-morning
also to a mole, who peeped out for a moment.
"Why don't you hop straight?" said Bevis presently. "It seems to me
that you hop first one side and then the other, and go in such a
zigzag fashion it will take us hours to reach the brook."
"How very stupid you are!" said the grasshopper. "If you go straight,
of course you can only see just what is under your feet; but if you go
first this way and then that, then you see everything. You are nearly
as silly as the ants, who never see anything beautiful all their
lives. Be sure you have nothing to do with the ants, Bevis; they are a
mean, wretched, miserly set, quite contemptible and beneath notice.
Now, I go everywhere, all round the field, and spend my time searching
for lovely things; sometimes I find flowers, and sometimes the
butterflies come down into the grass and tell me the news; and I am so
fond of the sunshine, I sing to it all day long. Tell me, now, is
there anything so beautiful as the sunshine and the blue sky, and the
green grass, and the velvet and blue and spotted butterflies, and the
trees which cast such a pleasant shadow and talk so sweetly, and the
brook which is always running? I should like to listen to it for a
thousand years."
"I like you," said Bevis; "jump into my hand and I will carry you." He
held his hand out flat, and in a second up sprang the grasshopper and
alighted on his palm and told him the way to go, and thus they went
together merrily.
"Bevis, dear, I do not sing at night; but I always go where I can see
a star. I slept under a mushroom last night, and he told me he was
pushing up as fast as he could before some one came and picked him to
put on a gridiron. I do not lay up any store, because I know I shall
die when the summer ends; and what is the use of wealth then? My store
and my wealth is the sunshine, dear, and the blue sky, and the green
grass, and the delicious brook who never ceases sing, sing, singing
all day and night. And all the things are fond of me; the grass and
the flowers, and the birds and the animals--all of them love me."
"I think I shall take you home and put you under a glass case on the
mantelpiece," said Bevis.
Off jumped the grasshopper in a moment, and fell so lightly on the
grass it did not hurt him in the least, though it was as far as if
Bevis had tumbled down out of the clouds. Bevis tried to catch him,
but he jumped so nimbly this way and that, and hopped to and fro, and
lay down in the grass, that his green coat could not be seen. Bevis
now went down to the brook and stood on the bank, where it was high,
near a bush at the side of the drinking place. "Ah, dear little Sir
Bevis!" whispered a reed, bending towards him as the wind blew,
"please do not come any nearer; the bank is steep and treacherous, and
hollow underneath where the water-rats run. So do not lean over after
the forget-me-nots--they are too far for you. Sit down where you are,
behind that little bush, and I will tell you all about the bathing.
The birds come down to bathe every Midsummer Day, and the goldfinches,
and the sparrows, and the blackbirds, and the thrushes, and the
swallows, and the wrens, and the robins, and almost every one of them,
except two or three, whose great-grandfathers got into disgrace a long
while ago. The rooks do not come because they are thieves, and steal
the mussels, nor the crows, who are a very bad lot; the swan does not
come either, unless the brook is muddy after a storm. The swan is so
tired of seeing himself in the water that he quite hates it, and that
is the reason he holds his neck so high, that he may not see more of
himself than he can help."
Soon the birds came. They were all in their very best and brightest
feathers, and as the sun shone on them and they splashed the water and
strutted about, Bevis thought he had never seen anything so beautiful.
They did not all bathe, for some of them were specially permitted only
to drink instead, but they all came, and all in their newest dresses.
So bright was the goldfinch's wing, that the lark, though she did not
dare speak, had no doubt she rouged. The sparrow, brushed and neat, so
quiet and subdued in his brown velvet, looked quite aristocratic among
so much flaunting color. As for the blackbird he had carefully washed
himself in the spring before he came to bathe in the brook, and he
glanced round with a bold and defiant air, as much as to say: "There
is not one of you who has so yellow a bill, and so beautiful a black
coat as I have." In the bush the bullfinch, who did not care much to
mix with the crowd, moved restlessly to and fro. The robin looked all
the time at Bevis, so anxious was he for admiration. The wood-pigeon,
very consequential, affected not to see the dove, whom Bevis longed to
stroke, but could not, as he had promised the reed to keep still.