in the eastern or the western hemisphere, has been struck by the
inconceivable profusion of the climbers and twiners with which the trees
are laced together. They are found from the thickness of a warship's
cable to that of pack-thread; the stronger ones often uncouthly twisted
together, and binding tree to tree. They are of the orders
_Malpighaceae_, _Apocyaneae_, _Asclepiadeae_, _Bignoniaceae_, &c., and often
are adorned with the most brilliant flowers.
I have before cited descriptions of these wonderful lianes, as they
occur in the forests of South America; my readers may like to peruse Sir
Emerson Tennent's graphic sketch of those of Ceylon:--
"It is the trees of older and loftier growth that exhibit the rank
luxuriance of these wonderful epiphytes in the most striking manner.
They are tormented by climbing plants of such extraordinary dimensions
that many of them exceed in diameter the girth of a man; and these
gigantic appendages are to be seen surmounting the tallest trees in the
forest, grasping their stems in firm convolutions, and then flinging
their monstrous tendrils over the larger limbs till they reach the top,
whence they descend to the ground in huge festoons, and, after including
another and another tree in their successive toils, they once more
ascend to the summit, and wind the whole into a maze of living network
as massy as if formed by the cable of a line-of-battle ship. When, by
and by, the trees on which this singular fabric has become suspended
give way under its weight, or sink by their own decay, the fallen trunk
speedily disappears, while the convolutions of climbers continue to grow
on, exhibiting one of the most marvellous and peculiar living mounds of
confusion that it is possible to fancy. Frequently one of these creepers
may be seen holding by one extremity the summit of a tall tree, and
grasping with the other an object at some distance near the earth,
between which it is strained as tight and straight as if hauled over a
block. In all probability the young tendril had been originally fixed in
this position by the wind, and retained in it till it had gained its
maturity, where it has the appearance of having been artificially
arranged as if to support a falling tree."[229]
Leaving the vegetable world, we may find some very curious examples of
parasitism among Insects. Every one who has paid the slightest attention
to this class of animals is aware that there are slender flies called
_Ichneumons_, whose grubs are hatched and reared in the bodies of other
insects. Many of these have the ovipositor greatly lengthened, and
projecting like a very slender needle from the extremity of the abdomen.
In some species, this needle-like organ is three or four times the
entire length of the body; and this great longitude is intended to reach
the pupae of wasps and similar insects which inhabit deep holes. The
needle itself is well worthy of study. It is not simple, but composed
of two pieces forming a sheath, which open and reveal a central finer
filament, furnished at its tip (in _Pimpla manifestator_, for example)
with saw-like teeth. With this instrument, which possesses great
elasticity and flexibility, the insect works, as a carpenter with his
brad-awl, boring through the clay, with which the wasp has closed up the
hole that contains her grub, until the tip of the ovipositor reaches the
soft body of the insect. Into this it pierces, and deposits an egg, and
is withdrawn. The slight puncture is scarcely felt by the grub, which
continues to eat and grow; the inserted egg, however, presently hatches,
and produces the ichneumon-grub, which begins to feed on the fat of the
wasp-grub, instinctively avoiding the vital parts, until the latter has
attained nearly its full size, and is ready to pass into the pupa state;
when, its vigour being gone, it fails to accomplish the metamorphosis,
the insidious intruder, now also full grown, taking its place, and by
and by issuing from the hole a perfect Ichneumon.
How often has the enthusiastic young entomologist been subjected to sore
disappointment by the parasitic habits of these _Ichneumonidae_! He has
obtained some fine caterpillar, a great rarity, and by dint of much
searching of his Westwood or his Stainton, feels quite certain that it
is the larva of some much-prized butterfly. He ascertains its leaf-food;
which it eats promisingly; all goes on encouragingly. Surely it cannot
be far from the pupa state now! When some morning he is horrified to
behold, instead of the chrysalis, a host of filthy little grubs eating
their way out of the skin of his beautiful caterpillar, or covering its
remains with their tiny yellow cocoons.
Some of these parasites are so minute that their young are hatched and
reared in the _eggs_ of other insects. Bonnet found that the egg of a
butterfly, itself no bigger than the head of a minikin pin, was
inhabited by several of the stranger grubs; for out of twenty such eggs,
he says, "a prodigious quantity" of the grubs were evolved.
A very interesting tribe of insects, so diverse from all other known
forms as to constitute an order among themselves, that of the
_Strepsiptera_, passes its youth in the bodies of certain wild bees. Mr
Kirby's account of his first detection of one of these, though often
quoted, is so interesting that I must cite it afresh. "I had previously
observed," he remarks, "upon bees something that I took to be a kind of
mite (_Acarus_), which appeared to be immovably fixed just at the
inosculations of the dorsal segments of the abdomen. At length, finding
three or four upon an _Andraena nigroaenea_, I determined not to lose the
opportunity of taking one off to examine and describe; but what was my
astonishment when, upon my attempting to disengage it with a pin, I drew
forth from the body of the bee a white fleshy larva, a quarter of an
inch in length, the head of which I had mistaken for an acarus (_bee
louse_)! After I had examined one specimen, I attempted to extract a
second; and the reader may imagine how greatly my astonishment was
increased, when, after I had drawn it out but a little way, I saw its
skin burst, and a head as black as ink, with large staring eyes and
antennae, consisting of two branches, break forth, and move itself
quickly from side to side. It looked like a little imp of darkness just
emerged from the infernal regions. My eagerness to set free from its
confinement this extraordinary animal may be easily conjectured. Indeed,
I was impatient to become better acquainted with so singular a creature.
When it was completely disengaged, and I had secured it from making its
escape, I set myself to examine it as accurately as possible; and I
found, after a careful inquiry, that I had got a nondescript, whose very
class seemed dubious."
Mr Newman, in an essay of much value,[230] has shewn that the larvae of
this tribe of insects are born alive, that they attach themselves to the
abdomens of wild bees, nestling among the hair, and that they are thus
introduced into the nest of the bee. Here it is somewhat uncertain how
they are sustained at first, for at this time the bee-grubs are not
hatched; probably they remain without food for some days, or devour a
portion of the pollen and honey stored up. As soon, however, as the
bee-grub is hatched, the Stylops-larva undergoes a metamorphosis, sheds
its six legs, and becomes a footless maggot; it pierces the soft skin of
the bee-grub, and feeds on its juices, till its maturity, as the
Ichneumon on the body of the caterpillar.
When the perfect bee emerges in the following spring, it bears the
full-grown Stylops, protruding from the rings of its abdomen. The latter
is in pupa, all the organs being distinct and separate, but wrapped
together, and inclosed in separate pellicles; very soon, it emerges, as
described by Kirby, and escapes, leaving a great unsightly cavity in the
body of the bee. This is the male: the female never escapes, but lays
its eggs on the bee in which it has been reared, and then dies.
In the spring we frequently see among herbage a great uncouth beetle of
a dark blue-black hue, with short wing-cases and long, heavy body, which
discharges drops of yellow fluid when handled, and is therefore called
the Oil-beetle (_Meloee proscarabaeus_). The early stages of this beetle
have much affinity with those of the _Stylops_. The beetle lays a number
of yellow eggs in a hole in the earth; these produce little active
six-footed larvae, resembling lice, which crawl to the summit of
dandelion and other flowers in the sunshine, and await the visit of a
bee. On the arrival of one, the active grub immediately clings to its
body, and is carried to the nest, not, however, to introduce itself
parasitically into the body of the bee-grub, but to feed on the
provision which the parent bee has stored up for its own young. Thus it
becomes very fat, and grows to a size much larger than that of the
full-grown bee-grub, having early dropped its six long clinging legs,
which, having performed their proper function in catching hold of a bee,
are no longer needed. It changes to a perfect beetle in autumn, lies in
the bee's nest all the winter, and emerges in the spring.
The large jelly-like Medusae which in summer are seen floating around our
coasts, driving themselves along by alternate contractions and
expansions of their umbrella, are frequently infested by little
creatures of widely different organisation, Crustaceans belonging to the
genera _Hyperia and Metoecus_. On the beautiful _Chrysaora_ of the
southern coast I have seen the _Metoecus medusarum_, a little shrimp
about half-an-inch in length, with enormous lustrous green eyes, which
takes up his residence in the cavities of the sub-umbrella,--dwelling in
them as in so many spacious and commodious apartments, of which he takes
possession, evidently without asking leave of the landlord, or paying
him even the compliment of a peppercorn rent. Here he snugly ensconces
himself, and feels so much at home, that he is not afraid to leave his
dwelling now and then, to take a swim in the free water, returning to
his chamber after his exercise; and here he rears his numerous family,
which, in the form of tiny white specks, very much unlike their parents
in shape, stud the membranes of the jelly-fish.
But, what is stranger still, Mr M'Cready has recently discovered in the
harbour of Charleston in North America, a _Medusa_ which is parasitic
upon another _Medusa_. _Cunina octonaria_ does not swim freely in the
water, but inhabits the cavity of the bell of _Turritopsis nutricula_.
"Not only does the latter furnish a shelter and dwelling-place for the
larvae during their development; it also serves as their nurse, by
allowing the parasites, whilst adhering by their tentacles, to draw
nourishment out of its mouth by means of a large proboscis. In point of
fact, the relation between them is of so unprecedented a nature, that
the author may well be excused for having at first taken the impudent
parasite for the gemmiparous progeny of the sheltering Medusa. The
youngest state of this parasitic Medusa observed by the author formed a
ciliated body of clavate form, adhering to the cavity of the bell by
means of the slender stalk in which it terminated. The first change
consists in the emission, from the thick end, of two slender flexible
tentacles, and in the formation of a central cavity by liquefaction. At
this stage of development, the author frequently observed gemmation
taking place at the thicker end, sometimes frequently repeated.
Subsequently the number of tentacles becomes doubled. These bend
together over the clavate extremity, and are then employed, instead of
the thin end of the body, in adhering to the cavity of the sheltering
Medusa. The thin extremity then acquires a mouth, and may be recognised
as a stomachal peduncle, which is employed, as above indicated, in
obtaining nourishment. The morphological nature of the proboscis becomes
still more distinct when, after the lapse of some little time, an
annular fold makes its appearance immediately under the tentacles, which
is recognisable from its form, and from the formation in it of (eight)
otolithic capsules, as the first indication of the future bell.
Simultaneously with the otolithic capsules, four rudimentary tentacles
make their appearance between the four tentacles. The Medusa remains in
this stage of development for a long time. The bell gradually becomes
more freely developed, and at last, by the reduction and entire
disappearance of the stomachal peduncle, becomes the most essential part
of the Medusa, after it has left its previous dwelling-place in the bell
of the _Turritopsis_. The bell nevertheless retains for some time its
earlier lobed form and unequal tentacles."[231]
More remarkable even than this association is the fact that certain true
Fishes habitually reside in the stomachs of star-fishes. This
circumstance, which had been observed in the Oriental Archipelago by MM.
Quoy and Gaimard, and by Dr Bleeker, has recently been confirmed by Dr
Doleschall, who has written a very interesting Memoir on it.
This learned naturalist states that the fact of the connexion between
the fish and the star-fish is well known to most of the fishermen in
Amboyna, and that he was able to obtain a sufficiency of specimens for
examination; but as the star-fishes (and with them the fishes) speedily
died in confinement, he was unable to make continuous observations upon
them in a living state. Of the results of his observations he gives the
following summary:--
"The fish stands to the star-fish in a definite relation which cannot be
the object of observation. Why the little fish should always seek the
stomachal cavity of one and the same species of star-fish, and not that
of various species, is a mystery. It is well known that Crustaceans of
the genus _Pagurus_ inhabit the empty shells of Mollusca; but we find
on the shore the same species of _Pagurus_ in the shells of the most
various genera and species.
"I have never met with _Oxybeles gracilis_, on the contrary, in any
other species of star-fish than _Culcita discoidea_. The fish was
described by Bleeker under the above name in 'Natuurkundig Tijdschrift,'
vii., p. 162. The author proceeds to state that neither he nor any one
else in Amboyna has ever captured the fish under other circumstances, or
while swimming freely in the sea; but upon this Dr Bleeker remarks that
many of his specimens of _Fierasfer Brandesii_, and all those of
_Fierasfer (Oxybeles) gracilis_ and _F. lumbricoides_, were obtained by
him along with other fishes, and were probably taken while swimming
freely in the sea.
"Upon the habits of _Oxybeles gracilis_ the author goes on to say that
it is certain that this animal passes the greater part of its existence
in the stomach of the star-fish, rarely shewing itself outside of this,
and then probably at night. That it does come out occasionally, appears
from the fact that in two cases the author observed the fish with a
portion of its body outside the cavity of the star-fish, and in the act
of creeping in.
"The same observations shewed that the fish, in returning to its
concealment, passes along the furrow of the lower surface of one of the
arms leading to the mouth of the star-fish, which is wide enough, when
the tentacles are retracted, to leave room for the passage of the
slender body of the _Oxybeles_. This fact likewise proves that the
_Oxybeles_ does not get into the stomach of the _Culcita_ by accident.
"If a living _Culcita_ be cut in two, the fish is seen moving freely in
the cavity of its body. If it be taken out, it immediately seeks the
shade. If the two halves of the _Culcita_ (still alive) be placed in the
water, the fish will soon be seen to draw towards them, in order to get
into the cavity of the star-fish. When exposed to the light, it is
uneasy, and its iris contracts excessively. The author never found two
fishes in the same star-fish.
"In most of the fishes examined by him, the author found the stomach
empty; it was full only in one. The contents of the stomach had the
appearance of a lump of fat, and consisted of half-digested muscle.
Under the microscope, striated muscular fibres could be detected, and
the author thinks that they belonged to the muscles of a fish. This
circumstance proves that _Oxybeles_ does not feed upon the chyle of the
star-fish, but that its nourishment is analogous to that of other
fishes. Whether it seizes upon the fishes taken by the star-fish for its
own nourishment must be determined by further investigations.
"The author's observations establish--
"1. That _Oxybeles gracilis_ is not a true parasite.
"2. That it passes the greater part of its life in the stomach of
_Culcita discoidea_, as is also indicated by the unusually pale colour
of the fish.
"3. That, however, it can come out, either to seek nourishment, or for
the purpose of reproduction.
"4. That it returns to the mouth along the furrow on the ventral surface
of the arms.
"5. That it is very sensitive to light.
"6. That it feeds upon other animals.
"In fresh water the animals live for about half-an-hour. The pigment
upon the peritoneum exhibits under the microscope the most beautiful
stellate forms. The fish possesses a swimming-bladder."[232]
Some very curious instances of parasitism occur, in which one kind of
creature compels or induces another creature to labour for its special
benefit. Indeed, in all cases, the parasite is benefited by the
functions of the supporter; but, in the cases I refer to, the slavery is
more special and more apparent.
There is a large species of Crab (_Dromia_) found in the West Indies,
which is invariably found covered with a dense mass of sponge. The
sponge is found to have grown in such a manner as to fit every
prominence and cavity of the crab, exactly as if a plastic material had
been moulded on it, yet it is not adherent to it, but is merely held in
position by the hindmost pair of feet, which in this genus of crabs, are
turned upwards, and apparently serve no other purpose than that of hooks
to hold on the sponge _in situ_.
On our own shores we are familiar with the Hermit crabs making use of
various kinds of univalve shells as houses to protect their softer
hindparts; but in many of these cases there is a third party in the
transaction, which is made to work for the crab's especial advantage.
The shell of the mollusk is sometimes covered with a sort of fleshy
polype-mass (_Hydractinia echinata_), which is parasitic on the shell.
The shell, however, being tenanted also by the active crab, the polype,
as it grows, moulds itself on the crab's body, and thus extends the
dimensions of its house, so that it has no necessity either to enlarge
its dwelling by the absorption of part of the interior shell-wall, or to
leave this shell and search for one of ampler size, as other
Hermit-crabs are obliged to do who have not the advantage of so
accommodating a fellow-lodger. "One can understand," says Dr Gray, "that
the Crab may have the instinct to search for shells, on which the coral
[polype] has begun to grow; but this will scarcely explain why we never
find the [polype] except on shells in which Hermit-crabs have taken up
their residence."[233]
Small Annelids and Crustaceans not unfrequently burrow into the stony
walls of corals; but Dr Gray records a much more uncommon case, from the
Guilding collection. "It is an expanded coral, which forms a thin
surface on the top of another coral, and is furnished with a number of
small, depressed, horizontal cases, opening with an oblong mouth. Some
of these contain within them a small, free, crustaceous animal, a
_Cymothoa_, which nearly fits the case; and it is evident that, by their
moving backwards and forwards on the surface, they have caused the
animal of the coral to form one of these cases for the protection of
each specimen."[234]
The manner in which this result is obtained is thus explained--"The
animals which form their habitation in corals, appear to begin their
domicile in the same way as the barnacles before referred to; they take
advantage of the soft and yielding nature of the animals which form the
corals, &c., and taking up a lodgement in their body, all they have to
do is to keep a clear passage in it, either by the moving backwards and
forwards, the exertion of their limbs, or the ingress or egress of water
to and from their bodies, and in time, as the coral is secreted by the
animal, it will form a wall round them; but if, by any accident, the
parasite animal should not keep a passage from the coral to the surface
of the body of the animal clear, which it must be constantly induced to
do, since by this means it procures food, the coral animal will in a
very short time close over it and bury it alive in the mass of the
coral; and this, from the number of these animals, of all sizes and in
different stages of growth, which are to be found in the substance of
the large and massive corals, must often be occurring. Thus the Italian
romance is often literally fulfilled in nature."
Certain birds are parasitic, in this sense, that they compel or induce
other birds to perform the labour of incubation and of rearing their
young. The Rhea or Ostrich of South America is parasitical on its own
species; the females laying each several eggs in the nests of several
other females, and the male ostrich taking all the cares of incubation.
More familiar examples, however, occur in our own Cuckoo, and in the
Cowpen birds (_Molothrus_ _pecoris_ and _M. niger_) of North and South
America. "These fasten themselves," as has been remarked by Mr Swainson,
"on another living animal, whose animal heat brings their young into
life, whose food they live upon, and whose death would cause theirs
during the period of infancy."
The habit, at least in the case of the European Cuckoo, is so well
known, that I need not do more than merely allude to the fact, that the
female seeks for the nests of other insect-eating birds, always much
smaller than itself, and deposits its own eggs,--a single egg in each;
that this stranger egg is hatched by the foster-mother with all care,
and the young bird is nurtured with all tenderness even at the expense
of its own proper eggs and young, which in general are sacrificed in the
course of the process. Every schoolboy knows these facts, but few
perhaps have ever suspected the existence of a romantic feeling of love
and fealty in the little bird towards the cuckoo herself, prompting the
rendering of the service required as a coveted honour. Yet a naturalist
has communicated to Mr Yarrell some facts which certainly look this way;
and because they are indubitably the very romance of natural history, I
cite them, leaving my readers to judge of their value.
"As you have contributed," writes Mr W. C. Newby of Stockton, "so much
to the information and amusement of the numerous class of readers who
take an interest in subjects of natural history, I consider it my duty
to communicate first to you, what appears to me a new fact in the
habits and character of that general favourite the cuckoo.