# The Zoologist/4th series, vol 3 (1899)/Issue 698/Biological Suggestions. Mimicry, Distant

part 2 of a series of five articles 'Biological Suggestions. Mimicry'. This part published in: The Zoologist, 4th series, vol 3, issues 698 (August, 1899), p. 341–363
BIOLOGICAL SUGGESTIONS. MIMICRY.
By W.L. Distant.
(Continued from p. 315.)
In all reflections on the wonderful adaptations in nature by which living creatures obtain a protection from their enemies by assimilative colour or structure, we must remember that in the struggle for existence fecundity plays no small part in producing survival. As De Quincey spoke of man in China as being but a weed, so throughout nature we often find excessive reproduction alone preventing extermination, and quite replacing the aid of protective or mimetic disguise in the "survival of the fittest." It is no longer the protection of the few, but the superfluous number of the attacked that militates against annihilation. As Mr. Harting has observed:—"The enormous rate of increase in fish, as compared with the rate of increase in their natural enemies, will always result in there being enough to spare for man and Otter—ay, for Kingfisher and Heron too." Weismann recognizes the same truth in the remark:—"No better arrangement for the maintenance of the species under such circumstances can be imagined than that supplied by diminishing the duration of life, and simultaneously increasing the rapidity of reproduction." Take the Orthoptera as found on the Transvaal veld—where most of these pages were written—which not only during the summer season literally supply the almost sole avian banquet, but are doubtless the prey of other enemies as well; and, although the usual colouration of these insects is more or less approximate to the short grasses among which they live, no apparent protection is afforded thereby, and their great reproductive powers seem their only protection against extinction. The American Lobster is another case in point. Mr. F.H. Herrick, of the United States Fish Commission, who suggests that its habits are the same as that of the European representative, states that out of the 10,000 eggs produced at one time, not more than two arrive at maturity, and that even that estimate is probably too high, as the fisheries are ​now declining. This diminution may well take place, for, according to Prof. Henry Woodward, of the common species Homarus vulgaris, as many as 25,000 live specimens "are often delivered at Billingsgate in one day. If only as many are eaten in the whole of England as in London, this would be at the rate of 50,000 per day, or 18,250,000 annually.... From Norway as many as 600,000 are received annually." Marine animals commonly produce far more eggs than insects. The dangers of the shallow seas are so great that a small proportion only of the young animals come to maturity. Hence the enormous fertility of common marine animals, except such as are able to nourish or defend their young. Vast numbers of Zoœa are swept into mid-ocean or into tidal rivers, or are devoured. It is only a chance remnant that survives. Prof. Möbius says that out of a million oyster embryos only one individual grows up, a mortality due to untoward currents and surroundings, as well as to hungry mouths. Leuckart calculates that a tapeworm embryo has only about one chance in 83,000,000 of becoming a tapeworm.
The fecundity of fish is shown by the following table of the number of ova in different species, as found by Frank Buckland's observations:—
| Name of Fish. | Weight of Fish. | No. of Eggs. |
| | lb. | oz. | |
| Salmon. (The average num- ber of eggs in a Salmon is 850 to each pound weight) | 12 | 0 | 10,000 |
| Trout | 1 | 0 | 1,008 |
| Carp | 14 | 8 | 633,350 |
| Perch | 3 | 2 | 155,620 |
| ,, | 0 | 8 | 20,592 |
| Name of Fish. | Weight of Fish. | No. of Eggs. |
| | lb. | oz. | |
| Jack | 28 | 0 | 292,320 |
| ,, | 32 | 0 | 595,200 |
| ,, | 4 | 8 | 42,840 |
| Roach | 0 | 12 | 480,480 |
| Conger Eel | 28 | 0 | 15,191,040 |
| Smelt | 0 | 2 | 36,652 |
| Lump Fish | 2 | 0 | 116,640 |
The Codfish (Gadus morrhua) is a good example of survival through fecundity. In a specimen weighing thirty pounds, with a roe of only four pounds and a quarter, it has been calculated that there were as many as 7,000,000 eggs, and in some cases the number may be 9,000,000. Here, besides other natural enemies, man again is a great destroyer. Describing the Codfishing off the coast of Labrador during the time of his visit (1833), Audubon writes:—"As there may not be less than one hundred schooners or 'pickaxes' in the harbour, three hundred boats resort to the bank each day; and, as each boat may procure two thousand Cods per diem, when Saturday night comes about six hundred thousand fishes have been brought to the harbour." According to Prof. Seeley:—"The banks of Newfoundland and adjacent coasts have been fished since the year 1500. Here one man may take upwards of five hundred fish in a day, and in a year he is reckoned to capture ten thousand, though sometimes fifteen thousand may be caught in a single voyage." As regards the wholesale destruction of the spawn of this fish, a single instance will suffice. In one bird colony alone on the wild coast of Norsk Finmarksen—that of Svaerholt-Klubben—are "millions upon millions" of the small Gull (Rissa tridactyla). The food of these multitudes of birds during the summer months consists for ​the most part of fish-spawn, more particularly that of the Codfish, which is abundant in these northern waters. The annual take of Herring is prodigious. It has been computed that a million of barrels, representing 800,000,000 fish, are taken in Scotland; the Norwegian Herring fishery is as productive as the Scotch fishery; the English, the Irish, the French, and the Dutch fisheries are also very productive. Estimating the gross produce of these four fisheries at only the same amount as the Scotch fishery, 2,400,000,000 Herring must be annually taken by these four nations—the British, the French, the Dutch, and the Norwegian. Yet the destruction of Herring by man is probably insignificant compared with that wrought by other natural agencies. Mr. James Wilson, in his 'Tour round Scotland and the Isles,' vol. ii. p. 106, says, when describing St. Kilda:—"Let us suppose that there are 200,000 Solan-Geese in the colony of St. Kilda (we believe, from what we saw, the computation moderate), feeding there or thereabouts for seven months in the year. Let us also suppose that each devours (by itself or young) only five Herrings a day—this amounts to one million; seven months (March to September) contain 214 days, by which, if we multiply the above, the product is 214,000,000 of fish for the summer sustenance of a single species near the island of St. Kilda." Cod and Ling, of which three and half millions were taken in Scotland in 1876, feed largely on Herring, six or seven being often found in the stomach of a Cod. These, it is thought, may consume twelve times as many Herring as the four nations together. Gannets, of which 10.000 dwell on Ailsa Craig, must catch more Herring than all the fishermen of Scotland; Whales, Porpoises, Seals, Codfish, Dogfish, predaceous fish of every ​description, are constantly feeding on them from the moment of their birth. The shoals of Herring in the ocean are always accompanied by flocks of Gulls and other sea-birds, which are continuously preying upon them, and it seems therefore no exaggeration to conclude that man does not destroy one Herring for every fifty destroyed by other enemies. The destructive power of man therefore is insignificant when it is compared with the destructive agencies which nature has created; and nothing that man has done, or is likely to do, has produced, or will probably produce, any appreciable effect on the number of Herring in the open sea. In 1781 the town of Gottenburg alone exported 136,649 barrels, each containing 1200 Herrings, making a total of about 164,000,000; but so rapid was the exhaustion of the fish from this keen pursuit, that in 1799 it was found necessary to prohibit the exportation of them altogether. This is a conclusion somewhat opposed to the opinion of Frank Buckland, as related above; but our aim here is only to show what multifarious dangers the Herring survives.
The Salmon deposits nearly a thousand eggs for every pound of its live weight. But nature is prolific in her waste, and a whole army of her poachers have to be satisfied. "So true is this, that the yearly yield of the largest Salmon-producing river in the kingdom is computed at about the produce of one female fish of from fifteen pounds to twenty pounds in weight." Mr. J.W. Willis Bund, the Chairman of the Severn Fishery Board, estimates that of Salmon eggs only 10 per cent., or 100,000 per million, hatch out. "Nothing Trout like better than Salmon ova; Eels regard it as a delicacy; while Water-hens, Water-Ouzels, Crows, and other birds, as soon as any part of the bed of the stream is either uncovered, or has only a few inches of water in it, go over it again and again, picking out the tit-bits the ova are to them." As to the mortality at the subsequent stages, estimating the number of ova hatched as 1,000,000 out of ​10,000,000 in the Severn, it is estimated that between 50 and 75 per cent. of the Alevins pass into the Fry stage, thus bringing the quantity to about 700,000. "In the Fry and Samlet stage the mortality increases to what degree is mere guess, as there is little, if any, evidence; but the mortality must be 50 per cent., so that there would be 350,000 Smolts. Among the Smolts there is also a very high rate of mortality, say, at least 75 per cent., so that the fish that reach the Grilse stage would be something like 40,000 out of 10,000,000 ova, or 4000 per million, about 4 per cent." In Kamschatka the Salmon have probably fewer enemies, as the rivers literally swarm with them; and Guillemard refers to one "little village" where, during the season, "20,000 fish would be no uncommon catch for a single day." The same author describes his impressions when standing on the banks of a little branch of the Avatcha River, not more than eighteen inches deep. "Hundreds were in sight, absolutely touching one another, and, as we crossed the river, our horses nearly stepped upon them. Their back-fins were visible as far as we could see the stream, and aground and gasping in the shallows, and lying dead or dying upon the banks, were hundreds more.... The millions of fish that are caught, and form the food throughout the year of almost every living creature in the country, are, however, as nothing compared with the countless myriads that perish naturally." Krashenniker, writing more than one hundred years ago, says:—"The fish come from the sea in such numbers that they stop the course of the rivers, and cause them to overflow the banks, and when the waters fall there remains a surprising quantity of dead fish upon the shore, which produces an intolerable stink." Guillemard considers that the vast majority—practically all, in fact—ascend the streams to spawn, and, having once done so, die. In the case of some species every fish appears to perish; in others a few get back to the sea. Besides other enemies, when Salmon are abundant and lie close a dreaded disease makes its appearance. This shows as a white fungus about the head and shoulders, and gradually spreads until the fish sickens and dies. The female ​Sturgeon (Acipenseridæ) deposits enormous numbers of extremely minute eggs, the product of a single individual having been estimated at upwards of three millions during a season. This fecundity is necessary to preserve the species, when, apart from other enemies, we read that upwards of fifteen thousand have been taken by fishermen in a single day at one of the fishing stations on the Russian rivers. Many other instances of great fecundity among fishes might be given, but at least reference may be made to the testimony of Mr. Henry Lee, that a large Octopus produces in one laying, usually extending over three days, a progeny of from 40,000 to 50,000; and the same authority, confirming the observations of Johann Bodasch, found that in the mop-like mass of spawn belonging to a Squid (Loligo vulgaris) there were probably 42,000 perfect young Squids.
Among mammals, the Rat is very prolific. Frank Buckland was told by a trustworthy Westminster ratcatcher that the Rat will breed every seven weeks, and that the female will begin to have young as early as fourteen weeks old. The same author, referring to a little book on the Rat written by a Mr. Shaw, "of ratcatching notoriety," states that "his little dog Tiny, under six pounds weight, has destroyed two thousand five hundred and twenty-five Rats, which, had they been permitted to live, would, at the end of three years, have produced one thousand six hundred and thirty-three millions, one hundred and ninety thousand, two hundred living Rats." "Every wild Rabbit who lives to old age has probably been concerned during its life as one of two partners in the production of not less than three hundred young Rabbits." Yet in England no perceptible increase is visible, and we must conclude "that out of three hundred Rabbits born, only two survive to middle age, on the average; the rest being either killed and eaten by carnivorous animals, or (more rarely) dying through inability, for some reason or another, to obtain food." The Hamster (Cricetus frumentarius) possesses marvellous powers of reproduction, and frequently appears in count​less swarms. They have a host of enemies, and Buzzards, Owls, Ravens, and other predaceous birds thin their ranks by hundreds; while among four-footed foes, Polecats and Stoats follow the track of the advancing legions, and kill them where and when they can. The Polecat and Stoat are, moreover, able to follow the Hamster into the recesses of their burrows, where they probably destroy them by hundreds.
Innumerable illustrations might be chosen from the life-histories of insects. Prof. Miall observes:—"Winter, of course, brings many hardships upon aquatic insects, as the great reduction in their number proves. The enormous number of eggs laid by so many of them is doubtless connected with the heavy risks to which they are exposed during half the year." Of one of the May-flies (Polymitarcys virgo) Réaumur states:—"The short life of the winged female compels her to deposit her 700 or 800 eggs at once, without much discrimination of likely and unlikely places." Of the Pine Sawfly (Lophyrus pini), whose larvae are frequently found in such numbers in pine-woods, it has been said:—"When young, and also just before turning into pupæ, the grubs are very susceptible to sudden cold or heavy rain, which kill off thousands. In addition to these destructive agencies, nearly forty different kinds of parasites infest the grubs, while mice devour numbers of the pupæ." Among the Threadworms (Nemathelminthes) parasitic Nematodes produce enormous numbers of eggs. Van Beneden states that 60,000,000 have been computed in a single Nematode, and this multiplication of ova is absolutely necessary, for the chance of the embryo reaching the right host, in which alone it can develop, is always a small one.
This excessive fecundity in some animal life finds its parallel in plants. Thus it has been computed that a plant of Sisymbrium sophia yields 730,000, one of Nicotiana tabacum 360,000, one of Erigeron canadense 120,000, and one of Capsella bursa-pastoris 64,000 seeds yearly. Probably in this case, and in a state of ​nature, a great check to increase is to be found in the difficulty the seeds experience in finding a proper soil in which to germinate, as well as in other sources of destruction.
The advantages of, or the part played by fecundity in the preservation of many species is evidently of the most complete and far-reaching character. This seems particularly and more frequently the case with fishes, the reasons for which are not difficult to comprehend. It has been urged that the pale colour of the under side of fishes makes it more difficult for enemies to detect them from beneath; but this is probably a truism without denoting any evolved protection, and may be due to other causes. The survival is probably owing to fecundity alone, which prevents extermination from the many foes and adverse conditions which environ their lives. One may stand before the tank in a large aquarium, and be impressed with the assimilative colouration of the upper sides of flat-fishes to the sandy or pebbly bottom on which they rest, but still no difficulty is experienced in distinguishing the living creatures; and if this be so, and with our untrained perceptions, how much stronger must be the detective powers of those natural enemies whose prey is their necessity! The 130,000 eggs said to be carried by a Sole of one pound weight is probably the factor which prevents annihilation, and not a moderate disguise which, without deceiving ourselves, is still less likely to mislead enemies whose lives depend on its destruction. Nature is here quite "careless of the single life," but, by fecundity, "so careful of the type." In our oceans and rivers the course of evolution has decided that the most prolific shall survive, and this is probably with fish the great factor of protection. Here individuality is lost, and Providence is with the big battalions. ​If there is truth in this view, it should be emphasized by the fact that animals of great fecundity, as a rule, possess little protective disguise in colouration or markings, and this, in a great measure, appears to be the case, despite the somewhat contrary evidence which tends to be deducible from the colours of many flat-fishes. Even in this case we must remember that other senses besides those of sight may be used to discover a semi-concealed prey. The extreme hardihood of certain animals after injury is also an agency in "survival." Prof. Mcintosh relates that "a full-grown female Picked-Dogfish was captured in the stake-nets for Salmon some years ago with its stomach distended with food. In dissecting the apparently dead animal in the laboratory the heart pulsated actively, though it and the pericardium were covered with old and recent lymph, caused by the irritation of a large Cod-hook, the point of which projected into the pericardium, and against which the heart seemed to impinge during contraction. An Eel will live for a year or two with a hook projecting through the gut into the abdomen, and the glutinous Hag (Myxine) is also hardy under similar circumstances." In so often seeking for the explanation of animal survival by mimetic or assimilative disguises, we are probably endeavouring to open too many locks with one key.
Colour alone may prove a false analogy to protection. Mr. Beddard has well observed:—"The bluish and white colour of many Gulls is generally allowed to be of protective value; in any case, they are not unlike their usual surroundings. For three years several of the common species of Gulls have a brownish speckled plumage, which is totally unlike that of the old bird; if one colour is advantageous, the other must be the reverse; and three years is either a considerable period, or not long enough." Another illustration is from a writer who, recording his views as to protective resemblances in South America, describes the wellknown butterfly, Ageronia feronica, which rests with its wings expanded horizontally. When seen on the "grey lichens or bark of the tree-trunk," it is "then so like in colour and markings to the surface on which it rests that it is practically invisible ​at the distance of even a few yards." This observer, however, at the same time refers to the statement of Bigg Wither, that this very insect is called the Whip-butterfly, owing to the sharp whip-cracking sound made by its wings when battling with its fellows in the air, and that this sound makes it the easy prey of a forest-bird, locally known as the "Suruqua," who thus detects and secures it. Here the apparent protection, by "protective resemblance," is invalidated by a peculiar and unusual sound-producing quality, which is as equally dangerous as its colour is reported protective. A similar remark may be made as to the musical Cicadidæ. How often have the usual green and brown colours of these insects been adduced as an example of protective resemblance, and not without reason if we regard only the difficulty of distinguishing them on the branches or leaves on which they rest. But when we desire to capture them, their shrill noise proclaims their retreat, and their assimilative colouration avails them little. This has frequently been the experience of the writer when in South Africa. Mr. Burr writes:—"I have often stalked down our large Locusta viridissima, L., and have usually found it on a bed of nettles or thistles, in the middle of a corn-field, or in stubble, invariably much farther away than I at first expected. The sound appears to come from almost beneath one's feet, but, on walking straight towards it, seems to recede into the distance, until it suddenly strikes the ear, very harshly and shrilly at close quarters. As soon as the would-be capturer approaches the sound ceases, and the insect remains invisible. The assimilation of the green colour of the insect and the green surroundings, which it always chooses as a band-stand, is so close, that it is almost impossible to detect the creature until it recommences to chirp, when the rapid movement of the elytra betrays its whereabouts." Frank Buckland wrote similarly of the Green Tree-Frogs of Germany:—"I have frequently heard one singing in a ​small bush, and, though I have searched carefully, have not been able to find him; the only way is to remain quite quiet till he again begins his song."
The aquatic larvae known as the Small "Bloodworm" (Tubifex rivulorum) is another instance of an animal whose colouration is a lure to its destruction, and whose fecundity can alone enable it to survive. The angler knows how readily a dish of Gudgeon can be procured with this bait; whilst other well-known ground fishes, such as the Loach (Cobitis barbatula), and the Miller's-thumb (Cottus gobio) also greedily attack it. These small worms live in great numbers in the mud at the bottom of streams, and, as Mr. Beddard has observed, as "the head-end is fixed in the mud, while the tail waves about freely in the water, these worms form exceedingly conspicuous red patches, which must attract ground-feeding fish."
It is often urged that few observers have seen butterflies attacked by birds, and that therefore their protective and warning colours are little needed against these as foes. Similar remarks have been made with reference to other animals. Thus Mr. Andrew Lang writes:—"On the Dee, Salmon sometimes rise to March Browns, and take the artificial March Brown tied rather large on these occasions. I have never seen a Salmon take a natural fly, any more than I have seen a phantasm of the dead"; yet he adds he "can believe on good evidence that Salmon do take natural flies." Undoubted trustworthy accounts do exist also as to avian attacks on Lepidoptera, and the writer has witnessed not a few, though the occurrence is somewhat uncommon. Eimer once came across a large concourse of white and blue butterflies on a high plateau of the Swabian Alp: "On my approach a number of birds (Stonechats) flew from the spot, and when I came up I found a number of maimed butterflies lying fluttering on the ground; pieces had been bitten from the wings of most of them—indeed the wings were often torn to pieces ​before the birds succeeded in getting the bodies of the butterflies, although these were sitting quietly on the ground." Mr. Riley Fortune states that he has often seen Starlings chasing butterflies. The Stonechat greedily devours butterflies, as I have seen in the aviaries of Dr. Butler. Zehntner on different occasions found seven Painted Lady butterflies in the mouths of Alpine Swifts (Cypselus melba), as recorded in the 'Catalogue des Oiseaux de la Suisse.' Such an observation did not miss the lynx eyes of Jefferies: "I once saw a Flycatcher rush after a buff-coloured moth, which fluttered aimlessly out of a shady recess; he snapped it, held it a second or two while hovering in the air, and then let it go. Instantly a Swallow swooped down, caught the moth, and bore it thirty or forty feet high, then dropped it, when, as the moth came slowly down, another Swallow seized it and carried it some yards and then left hold, and the poor creature after all went free. I have seen other instances of Swallows catching good-sized moths to let them go again." These moths were probably inedible species, and were thus protected, at least at this stage of their existence. Mr. Furneaux, referring to the common and well-known white butterflies of the British Pieridæ, observes: "It is remarkable that we are so plagued with 'whites' seeing that they have so many enemies. Many of the insect-feeding birds commit fearful havoc among their larvae, and often chase the perfect insect on the wing." Another writer states: "At no stage in their lives are lepidopterous insects free from the attacks of enemies. In the egg state they fall a prey to beetles and small birds, and as larvæ they are extremely liable to receive a deadly thrust with the ovipositor (or sting) of an ichneumon.... The enemies of the imago, whether butterflies or moths, are numerous. Birds, Bats, dragonflies, &c, pursue and harass them whenever they happen to meet with them." Fungi are also parasitic on butterflies. But the discrepancy in experience as found among ​field naturalists on these points tends to prove how partial or moderate must be the danger in the present day, and how considerably more intense it must have been in some former time to have prompted the evolution of the wonderfully simulating guises, which we can only conceive as evolved for protective purposes.
A repetition of observations will frequently qualify the premises on which many conclusions are based. Many recorded facts are of course utterly erroneous. Thus in 1666 Schefferus records in the 'Philosophical Transactions' that Swallows sink into lakes in autumn, and hibernate in a manner precisely similar to Frogs. In 1741 Fermier-Général Witkowski made legal testimony to the effect that two Swallows had been taken from a pond at Didlacken in his presence in a torpid state; that they eventually regained animation, and after fluttering about, died some three hours after their capture. In 1748 the great Swedish chemist Wallerius wrote that he had on several occasions seen Swallows clustering on a reed until they all disappeared beneath the surface. Thus a traveller in a tropical forest might from paucity of observation form a wrong impression as to the relation of the liane and the stem or tree to which it is attached. He would frequently find "the hard basal parts of a liane stem twisted and coiled apparently around nothing. This is due to the fact that the original support had been killed, and then, slowly rotting into dust, has been denuded away by the wind and rain." Our traveller might then record the murderous action of lianes as of a somewhat universal character. But further observations would show the action quite reversed. As Kerner describes the process: "If the erect young stem is stronger and more vigorous than the twiner which encircles it, which has been used as a prop, it does not allow itself to be strangled; the twiner is destroyed when they both increase in thickness. The coils of the climber are gradually stretched tighter and tighter, and many are the contrivances which exist for preventing the tension from immediately acting injuriously on the movement of the sap in the interior of the twining liane stem. As this thickening continues, the pull on the coils becomes so great that the death of the liane results." ​Similarly an explanation may be long deferred till one branch of science is sufficiently advanced to illuminate another. Discoveries in botany and entomology have often reacted on, and supplemented each other. Prof. Drummond has quoted an instance which will serve our purpose here:—"More than two thousand years ago Herodotus observed a remarkable custom in Egypt. At a certain season of the year the Egyptians went into the desert, cut off branches from the wild palms, and, bringing them back to their gardens, waved them over the flowers of the date palm. Why they performed this ceremony they did not know; but they knew that if they neglected it the date crop would be poor or wholly lost. Herodotus offers the quaint explanation that along with these branches came certain flies possessed of a 'vivific virtue,' which somehow lent an exuberant fertility to the dates. But the true rationale of the incantation is now explained. Palm trees, like human beings, are male and female. The garden plants, the date bearers, were females; the desert plants were males; and the waving of the branches over the females meant the transference of the fertilizing pollen dust from the one to the other."
The time has arrived when the whole theory of "protective resemblance" and (or) "mimicry" requires to be expressed and understood in two senses, viz. Demonstrated, and Suggested or Probable. I propose also to give instances of what may be considered as Disputed or Mistaken Mimicry, and likewise Purposeless Mimicry. In considering these questions one is reminded of the three kinds of Phantasms as understood by the Stoics. Those that were probable, those that were improbable, and those that were neither one nor the other. Or perhaps still better, the three categories of Renan. "The first, which is unfortunately very limited, is the category of certainties; the ​second, that of probabilities; and the third, that of dreams," By the term "Demonstrable" is implied all those instances where protection, absolute or partial, has been or can be demonstrated by experiment or actual observation. "Suggested or Probable" should, however, be applied to those examples where, because we see similarity of structure, markings, or colour, we assume—and probably often correctly—that protection is involved, though no direct knowledge of the same is obtainable. As an illustration, we know that certain Diptera, Eristalis spp., resemble Bees, and we conclude that this simulation has arisen by evolutionary means for protective purposes. It must nevertheless be remembered that the Bee itself is not absolutely protected by its sting, and does not possess a corresponding immunity from the attacks of all its enemies. Mr. Woodford, on Peel Island, Moreton Bay, observed Bees of the genus Bombus caught and devoured by Spiders. Prof. Lloyd Morgan's experiments, however, demonstrate protection at least from birds:—"To another group of chicks I just gave Hive Bees, which were seized, but soon let alone, and then the Droneflies (Eristalis), which so closely mimic the Hive Bee. They were left untouched. Their resemblance to the Bees was protective." Frank Buckland relates:—"A gentleman in Oxfordshire had a hive of Bees in the cavity of a wall. A common Toad which had taken up its residence in a hole close by was observed to walk forth and place himself at the mouth of the hive, and so catch the Bees in their coming from and returning to the hive with much dexterity and activity. After witnessing the Toad at work for some time, and feeling convinced that, if his depredations were suffered, he would eventually destroy the whole hive, the owner of the Bees killed the robber, and on inspecting his stomach it was found full to repletion of dead Bees."
​No specialist who works long at any large group of animal forms, especially at insects, can escape meeting with these problems. This is particularly discovered when, in monographing a family, species are found resembling insects belonging to another order. Thus, in recently working out some Hemiptera for the 'Biologia Centrali-Americana,' I found in the family Lygæidæ a species with all the superficial form and colour of an Earwig (Forficula) belonging to the order Orthoptera; while among the Lygæidæ and Capsidæ were many species which mimicked Ants (Hymenoptera). To add to the problem, Lygæidæ and Capsidæ were found mimicking one another. Dr. Thorell made a similar observation in monographing Burmese Spiders. Ligdus chelifer "is a small flat Spider belonging to the family Salticoidæ, and resembles very much a Cheloneth (Pseudoscorpion); Prolochus longiceps has some resemblance to an Orbitelarian Spider of the genus Meta (M. segmentata, f. inst.)." Now, in the first case, and, alluding to the writer's own experience, it appears we have "Suggested or Probable Mimicry," because we possess no knowledge whether these Hemiptera are found with the Earwigs and Ants they mimic, nor whether they are avoided or neglected by enemies because of this mimicry. We can only report that these insects are mimics one of another as seen in our cabinets, and that as nothing is, or can be, predicated as purposeless in nature, neither can these assimilative forms be meaningless; and, further, arguing from demonstrated knowledge in other cases of mimicry being protective, the presumptive evidence is that the theory of protection affords the clue to the origin of the mimetic guise of these insects. But this is only circumstantial evidence of the weakest description, and, though we may believe as a matter of biological faith, based on analogous cases in nature, that this is the explanation, it is probable, or more than probable, that the progress of science is retarded by confounding scientific suggestion with ​scientific demonstration. It is simply teleology come back to the house newly swept and garnished. To the teleologist everything in nature proclaimed design, and a precisely similar view—only differing in terminology—is held by an extreme wing of our own Darwinian army; the only distinction is, that the design in one case was attributed to a supernatural providence, in the other, to an all-sufficing power represented by the term Natural Selection. That the teleologist was in no way inferior, but in many instances—so far as power of observation was concerned—surpassed the knowledge of many of our contemporary entomological evolutionists, is a fact that can be easily realized by perusing the exhaustive Letter XXI. in Kirby and Spence's 'Introduction to Entomology,' on "The means by which insects defend themselves." In this letter may be found a wealth of illustration on what we understand as "protective resemblance," &c, not available in any special work written on that theory. How near to modern thought the writer of that letter was, is proved by its last paragraph:—"Another idea that upon this occasion must force itself into our mind is, that nothing is made in vain. When we find that so many seemingly trivial variations in the colour, clothing, form, structure, motions, habits, and economy of insects are of very great importance to them, we may safely conclude that the peculiarities in all these respects, of which we do not yet know the use, are equally necessary; and we may almost say, reversing the words of our Saviour, that not a hair is given to them without our Heavenly Father." Even when teleological views and the conception of a special creation dominated the minds of naturalists, the knowledge of the existence of intermediate forms—a postulate of modern evolution—was more or less enunciated. Thus, in the first part of the 'Zoological Transactions,' Mr. Ogilby, in describing the Cynictis Steedmanii, a mammal just then discovered in South Africa, remarks: "That the work of creation was originally complete and perfect in all its ​parts; that no hiatus existed among natural bodies, or, in other words, that no individual stood completely apart from surrounding groups, but that all were connected by a uniform gradation of intermediate forms and characters, is a law of natural history which every day's experience tends more strongly to confirm." We sometimes find teleological views in what are presumably put forward as evolutionary suggestions. Thus Mr. Harting, in discussing the migrations of Ceylonese butterflies, is inclined to concur with Col. Swinhoe, in considering the explanation "as a sudden exodus from the birthplace, leading to a compensating reduction of the species, after a season exceptionally favourable to its increase." This "compensating reduction," or rather the method of the same, as thus expressed, seems more logically to denote design or chance, neither of which will explain the phenomena, but may reasonably be adduced to account for the theory. Perhaps one of the most orthodox and thoroughgoing teleologists was the late Frank Buckland, to whom the poisonous fangs of deadly Snakes were "the apparatus which the omniscient Creator has given to the class of Snakes to enable them to procure their food"; though, he might have added, these divinely-constructed creatures are on that very account gladly destroyed by the orthodox and heretical alike. The real difference between the teleologist and the evolutionist appears to be this. Both search for the phenomenal facts in animal life, but, when found, the teleologist goes no further than enunciating the magical word "Design." The evolutionist, on the contrary, seeks to find how the structure or property has been, and from whence, derived. With the first it is "Fall down and worship"; with the second, "Prove all things." Agassiz considered that the only classification of the animal kingdom was to be found in the plan of creation; "the free conception of the Almighty Intellect matured in His thought before it was manifested in tangible external forms." And again: "I would as soon cease to believe in the existence of one God because men worship Him in so many different ways, or because they even worship gods of ​their own making, as to distrust the evidence of my own senses respecting the existence of a pre-established and duly-considered system in nature, the arrangement of which preceded the creation of all things that exist."
What we seem to require is a healthy Agnosticism in theoretical science; neither affirmation nor negation, per se, but proof. Thus, grant to all a free use of the imagination in scientific theory, but in no case allow it to be confounded with fact, or crystallized into dogma. "What is called 'mimicry' is apparently, in many cases, nothing more than the influence of similar surroundings, acting in a similar manner upon different insects inhabiting the same district." Or, as Mr. F.T. Mott most enigmatically puts the objection, "The very curious appearances of mimicry, which are often supposed to be protective, but of which a large proportion seem to have no such function, may probably be attributed to sympathetic communication of the vibratory motions which must be passing through the ether in all directions in the neighbourhood of organic life." Animal depredators may, however, be not altogether defeated by "mimicry," which of course predicates the sense of sight only. As Mr. Cornish has well observed, predaceous animals watch for movement to guide them to their prey. "Most of the larger birds, notably Wood Pigeons, remain perfectly motionless for many seconds after alighting in a new place, in order to identify any moving object. On the other hand, the power of scent is a great corrective to animal misconceptions about objects." How little is the cause of Darwinism advanced by many exhibitions made at scientific societies! The advocate exhibits—say, insects—which, belonging to different orders, closely resemble each other in colour, markings, or structure, and which he reasonably adduces as an example of "mimicry," but misuses a suggestion as a demonstration. The Darwinian sceptic at once denies the strength of the whole argument, because it cannot be demonstrated as a fact, and has not been put forward as a suggestion only. It is quite possible ​that truth may exist between the two antagonists, for it seems certain we have not yet all the explanations of these mimetic disguises, and discussion may well precede a universal dogma of its causation. Because a phenomenon is frequent in nature, it is not necessarily universal. For instance, the metamorphosis in the early lives of Frogs is an observation of so general a nature as to indicate a constant law; but a land Frog in the Solomon Islands (Rana opisthodon) lays very large eggs in the crevices of rocks, and from these emerge fully-developed Frogs. We join issue with Prof. Tyler when he states, "Natural science does not deal in demonstrations, it rests upon the doctrine of probabilities; just as we have to order our whole lives according to this doctrine." This is a cardinal doctrine in natural and apologetic theology, but is the very antithesis of science, natural or otherwise. The man who orders his whole life on probabilities will probably arrive at the conclusion that hope is a very good breakfast, but a most indifferent dinner. A "science" based on probabilities may turn out to be a new system founded on contradictions.
Prof. Herdman, in speaking of the colours of Nudibranchs and their probably protective character, forcibly observes that we cannot gauge the problem by observing the animals in a museum-jar, or as illustrated in a book, or on the wall. "In order to interpret correctly the effect of their form and colours, we must see them alive and at home, and we must experiment upon their edibility or otherwise in the tanks of our biological stations." Such a course would doubtless give many positive and many negative results, confirming in many cases the theory—if it is still to called but a theory—of mimicry, and preventing many hasty and erroneous conclusions in other cases, where mimicry is only a suggestion, and much discredit is brought to the argument. The "law of evidence" might with advantage be studied ​by many enthusiastic students in bionomics. Solitary instances, or that of a single species without reference to its congeneric allies, afford but a doubtful testimony to mimetic resemblances. This was clearly seen and enunciated by Darwin himself:—"If Green Woodpeckers alone had existed, and we did not know that there were many black and pied kinds, I dare say that we should have thought that the green colour was a beautiful adaptation to conceal this tree-frequenting bird from its enemies; and consequently that it was a character of importance, and had been acquired through natural selection; as it is, the colour is probably in chief part due to sexual selection." In fact, much evolutionary controversy is simply intellectual fencing, and what Schopenhauer has defined as "controversial Dialectic, Dialectica eristica." Mimicry, again, is often much obscured by plates in illustrated books which are intended to support the theory. As an example, in the excellent 'Royal Natural History' appears a coloured plate, entitled "Mimicry in Insects." Here a number of various insects of different orders and diverse habits are brought together in the midst of inappropriate—or inartistic—foliage, with the result that there is no apparent or sufficient mimicry to deceive the most careless enemy, or the most inexperienced entomologist. In fact, as a support to the theory, one can only conclude that either nature, or the artist, is at fault. Again, a comparative immunity from attack is often ultimately proved to be alone the case. A recent writer has observed:—"It is well known, and I have myself observed, that all our 'Cabbage' Butterflies are immune from attacks of birds, presumably because of some unpleasant taste or smell. Wasps, however, have twice been observed by me in the act of devouring these butterflies. Earwigs, too, which undoubtedly possess an unpleasant smell when irritated, fall victims to Wasps, in spite of their malodorous attributes."
To conclude a discursus, which in itself appears somewhat controversial, it may be better to give some instances of ​what are considered as "demonstrated," and others classed as "suggested or probable," illustrations of the theory of mimicry; and it will be noticed that those in the second category are much more numerous than those included in the first; inference necessarily having so often to be relied upon in the absence of observed facts.
(To be continued.)
* ↑ 'Zoologist,' 3rd ser. vol. xviii. pp. 44–5
* ↑ 'Lectures on Heredity,' &c. Eng. Transl. 2nd edit. vol. i. p. 17
* ↑ 'Zoologischer Anzeiger,' xvii. no. 454; summarized in 'Nature,' vol. l. p. 553.
* ↑ 'Cassell's Nat. Hist.' vol. vi. p. 205; also cf. W.B. Lord, 'Crab, Shrimp, and Lobster Lore,' p. 95.—According to Bertram, 'As a general rule, the great bulk of Lobsters are not much more than half the size they used to be' ('The Harvest of the Sea,' p. 274).
* ↑ L.C. Miall, 'Nature,' vol. liii. p. 154.
* ↑ Cf. Thomson, 'The Study of Animal Life,' 2nd edit. p. 43.
* ↑ Ibid. p. 48.
* ↑ "There is not a living creature," said Mr. Francis Francis, "which inhabits the waters which does not prey more or less on Trout ova." ("The Trout" (Fur, Feather, and Fin Series), p. 171.)
* ↑ The number of eggs produced by this fish has been given as much greater by more recent writers. "Upwards of two hundred and eighty thousand have been taken from a fish of half a pound in weight" ('Royal Nat. Hist.' vol. v. p. 336).
* ↑ 'Life of Frank Buckland,' by G.C. Bompas, 2nd edit. p. 252.—"A Turbot of 8 lb. carries 300,000 eggs; a Sole of 1 lb. 130,000 eggs" (Ibid. p. 263).
* ↑ It has been suggested that the greatest loss to the succeeding generation takes place at the very earliest stage of the egg, in that a large proportion of the ripe eggs discharged in the water are not fertilized by the spermatozoa, and hence perish (Mcintosh and Masterman, 'The Life-Hist. Brit. Marine Food Fishes,' p. 236).
* ↑ 'Audubon and his Journals,' vol. ii. p. 422.
* ↑ 'Cassell's Nat. Hist.' vol. v. p. 59.
* ↑ G. Lindesay, 'Fortnightly Review,' November, 1894.—Codfish are also infested with parasitic Copepoda. According to Surgeon Bassett-Smith, it is rare to find a fairly grown Cod without being able to take many specimens of the small semitranslucent Anchorella uncinata attached to the folds about the lips and in the gill-cavity. In its mouth and on the palate will be seen frequently half a dozen specimens of Caligus curtus; on the gills, deeply embedded, a Lernea branchialis, and on the body sore places where a number of Caligus müllleri have been fixed. And, although this investigator con- siders that in the great majority of cases these parasites are not prejudicial to the life of the fish, he describes Lernea branchialis as a certain exception to the harmless rule (Ann. & Mag. Nat. Hist. 6th ser. vol. xviii. pp. 9 and 10).
* ↑ Cf. J.M. Mitchell, 'The Herring, its Nat. Hist, and National Importance,' p. 37.
* ↑ 'Life of Frank Buckland,' by G.C. Bompas, 2nd edit. pp. 313–14.
* ↑ 'Das Leben des Meeres,' p. 182.—Cf. Marsh, 'Man and Nature,' p. 120, note.
* ↑ The excessive spermatozoa of the Herring sometimes whitens the water for scores of square miles (Matthias Dunn, 'Contemp. Rev.' lxxvi. p, 200).
* ↑ Thomas Watson, 'Poachers and Poaching,' p. 165.
* ↑ 'The Life of a Severn Salmon,' p. 7.
* ↑ 'The Life of a Severn Salmon,' p. 11.
* ↑ 'Cruise of the Marchesa,' 2nd edit. p. 68.
* ↑ Ibid. p. 73.
* ↑ Ibid. p. 92.
* ↑ John Watson, 'Sketches of British Sporting Fishes,' pp. 3–4.
* ↑ 'Royal Nat. Hist.' vol. v. p. 514.
* ↑ Cf. H. Woodward, 'Cassel's Nat. Hist.' vol. v. pp. 161 and 166.
* ↑ 'Curiosities of Nat. Hist.' Pop. edit. vol. i. p. 69.
* ↑ Ibid. p. 70.
* ↑ Wells and Davies, 'Text-Book of Zoology,' p. 128.
* ↑ Lydekker, 'Roy. Nat. Hist.' vol. iii. p. 126.
* ↑ 'Nat. Hist. Aquatic Insects,' p. 18.
* ↑ F.O. Pickard-Cambridge, 'Roy. Nat. Hist.' vol. vi. p. 17.
* ↑ Cf. A.E. Shipley, 'Cambridge Nat. Hist.' vol. ii. p. 162.
* ↑ Kerner and Oliver, 'Nat. Hist. Plants,' vol. ii. p. 878.
* ↑ Of course it is not suggested that all fish survive through fecundity alone. The European Goby (Latrunculus pellucidus) and the Sea-Stickleback (Gastrosteus spinachia) have apparently been proved to die within a year of their birth. In these cases other protection seems to be afforded. According to Dr. Günther, the fish spawns in June and July. In April the males lose the small teeth, which are replaced by very long and strong teeth, the jaws themselves being stronger. The teeth of the females remain unchanged. In July and August all the adults die off ('Introd. Study Fishes,' p. 487). In this case the male may defend the progeny. G. spinachia is, on the same authority, a "nest builder, choosing for its operations especially the shallows of brackish water which are covered with Zostera." (ibid. p. 507).
* ↑ 'Journal of Mental Science,' April, 1898.
* ↑ 'Animal Coloration,' 2nd edit. p. 29.
* ↑ C.W. Tait, 'Entomologist,' vol. xxvii. p. 52. (The author's name by a misprint appears as W. C. Mit.)
* ↑ That birds do destroy Cicadas is a fact well known. Mr. Blanford found the Accipiter Nisus sphenurus, in Abyssinia, "living on Cicadæ" ('Obs. Geol, and Zool. of Abyssinia,' p. 295). Cf. also Swinton ('Insect Variety,' p. 21); Belt ('Naturalist in Nicaragua,' p. 230); Hudson (Trans. N. Zeal. Instit. vol. xxiii. p. 20); Riley ('Science,' v. p. 521).
* ↑ 'Zoologist,' 4th ser. vol. i. p. 516.
* ↑ 'Life of Frank Buckland,' by G.C. Bompas, 2nd ed. pp. 56–7.
* ↑ 'Animal Coloration,' 2nd edit. p. 6.—According to Prof. Miall, the colour of the larva of Chironomus is due to a blood-red pigment, which is identical with the hæmoglobin of vertebrate animals, and "only such Chironomus larvæ as live at the bottom and burrow in the mud possess the red hæmoglobin" ('Nat. Hist. Aquatic Insects,' p. 130).
* ↑ 'Illustrated London News,' February 10th, 1894.
* ↑ 'Organic Evolution,' Eng. Transl., p. 118.
* ↑ 'Ornithology in relation to Agriculture and Horticulture' (1893), p. 139.
* ↑ Cf. Gurney, 'Trans. Norf. and Norw. Nat. Soc.,' vol. vi. p. 259.
* ↑ 'Wild Life in a Southern Country,' p. 147.
* ↑ 'Butterflies and Moths' (British), p. 144.
* ↑ F.O. Pickard-Cambridge, 'Roy. Nat. Hist.,' vol. vi. p. 80.
* ↑ J.C. Rickard, ' Entomologist,' vol. xxix. p. 170.
* ↑ Cf. Dixon, 'The Migration of Birds,' 2nd edit. p. 54.
* ↑ Kerner and Oliver, 'Nat. Hist. Plants,' vol. i. p. 682.
* ↑ 'The Ascent of Man,' pp. 310-11.
* ↑ The term "mimicry" is often considered as first applied in nature by its great enunciator, H.W. Bates. Some years ago I pointed out ('Rhopalocera Malayana,' p. 33, note) that Henfrey in 1852 had already used the term in connection with botany. Mr. Scudder subsequently ('Butterflies E. U. States and Canada,' vol. i. p. 710) showed that Kirby and Spence had anticipated Henfrey in 1815. Boisduval also, in 1836, drew attention to the phenomena (cf. Coe, 'Nature versus Natural Selection,' p. 161).
* ↑ 'Philosophical Dialogues and Fragments,' Eng. Transl., p. 5.
* ↑ 'A Naturalist among the Head-hunters,' p. 70, note.
* ↑ 'Habit and Instinct,' p. 52.
* ↑ 'Curiosities Nat. Hist.,' pop. edit., vol. i. pp. 42–3.—According to Mr. Pocock, and as a result of an experiment, a Spider treats both Bee and Eristalis with the same caution when found in its web ('Roy. Nat. Hist.,' vol. vi. p. 62). That the Bee has no special immunity is attested by Mr. Pickard-Cambridge, who states that another hymenopterous insect, Philanthus triangulum, in its larval condition feeds upon the Honey Bee. "Since at least five Bees are provided for each larva, the havoc caused in hives where these insects abound must be considerable " (ibid. p. 36). The Horse Bot Fly (Gastrophilus equi) also resembles the Honey Bee in size, colour, and form, but protective mimicry here seems an altogether unwarranted assumption, as the larval fly is parasitic in the alimentary canal of the Horse.
* ↑ 'Descrip. Catalogue Spiders of Burma,' Introd. p. xiii.
* ↑ According to Prof. Miall, when writing on 'Flies with Aquatic Larvæ,' "The attitude, the mode of breathing, and the mode of feeding observed in the larva of Dixa are curiously like those of a certain Gnat larva, Anopheles. So close is the resemblance, that an experienced entomologist has, in a published paper, mistaken one for the other. There are few better examples of adaptive resemblance" ('Nat. Hist. Aquatic Insects,' p. 163). But the reasons why this should be considered as adaptive resemblance are not stated.
* ↑ Cf. Steedman, 'Wanderings and Adventures in the Interior of Southern Africa,' vol. ii. p. 97.
* ↑ 'Zoologist,' 3rd ser. vol. xix. pp. 340–1.
* ↑ 'An Essay on Classification,' p. 10.
* ↑ 'An Essay on Classification,' p. 228.
* ↑ W.F. Kirby, 'A Handbook to the Order Lepidoptera,' vol. iv. p. xxiv.
* ↑ "Organic Colour," 'Science,' June 16th, 1893.
* ↑ 'Animals of To-day,' p. 165.
* ↑ Guppy, 'The Solomon Islands,' p. 316.—Hylodes martinicensis affords another instance (cf. Mon. Berl. Ac. 1876, p. 714).
* ↑ 'The Whence and the Whither of Man,' p. 164.— It is only fair to add that this is a book written by an American Professor of Biology, consisting of a series of Morse Lectures delivered at a "Union Theological Seminary," on the agreement that the subject of the lectures was to have to do with "The relation of the Bible to any of the Sciences."
* ↑ Opening Address, Sect. Zoology, Brit. Assoc. Ipswich, 1895.
* ↑ 'Origin of Species,' 6th edit. p. 158.
* ↑ Vol. vi.
* ↑ This is a direct contradiction to the testimony of Mr. Furneaux (cf. ante, p. 328).
* ↑ O.H. Latter, 'Natural Science,' vol. vi. p. 151.
* ↑ Of course by this term is meant what has been or can be demonstrated, and hence a careful observation made by a competent traveller must be accepted as decisive, for we can neither all visit the scene of the occurrence nor, if we could, is it certain we might meet with the instance. A remark by Lecky is apposite:—"If anyone in a company of ordinarily educated persons were to deny the motion of the earth, or the circulation of the blood, his statement would be received with derision, though it is probable that some of his audience would be unable to demonstrate the first truth, and that very few of them could give sufficient reasons for the second" ('Rationalism in Europe,' vol. i. p. 9).
This work was published before January 1, 1929, and is in the public domain worldwide because the author died at least 100 years ago.
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