Page images
[ocr errors]
[ocr errors]
[ocr errors]

the State. Melons from Rocky Ford and peaches from Mesa the School of Mines, at Golden : the Agricultural College, at Fort county are shipped to the east, and in small quantities to Europe. Collins ; the Normal School, at Greeley; the School for the Deaf The report for 1898 shows that the staple grains gave the following and Blind, at Colorado Springs; the Industrial School for boys, at yield in bushels : wheat, 6,729,565 ; corn, 3,113,892 ; barley, Golden, and for girls at Aurora. These are supported by a mill 353,952 ; oats, 3,063,191 ; rye, 47,484. The hay product was tax, and special appropriations. The State University has an 1,760,728 tons, and potatoes 2,564,331 bushels. The total value of annual income of $70,000, and a library of 19,000 volumes; the these products was estimated at $17,349,251, as against $3,047,750 School of Mines, an income of $37,000; and the Normal School in 1882. It has been discovered by experiments conducted by the an income of $32,000, and a library of 10,000 volumes. The AgriUnited States Government, through the Agricultural College, that cultural College has an income of $65,500, of which $23,000 is from the soil along the South Platte, the Arkansas and Grand rivers, the United States Government. Experiment stations are conducted and also in the San Luis Valley, is adapted for the cultivation of in connexion with the college at Fort Collins, Rocky Ford, and sugar beets, the average crop being 16 tons to the acre, and the Cheyenne Wells. There are two institutions for higher education proportion of saccharine matter unusually large. Sugar factories on an independent foundation. Colorado College, at Colorado have been built at Grand Junction, Rocky Ford, and Sugar City ; Springs, is the oldest existing college in the State. Its property the first with a daily capacity of 3500 tons, and the others of 7500 in equipment and endowment is $1,500,000, and it has a library of tons. Stock-raising has always played an important part in the 30,000 volumes. The University of Denver, under Methodist condevelopment of the State. The native grasses are especially adapted trol, is an outgrowth of the Colorado Seminary, the charter of for fodder. The grama, buffalo, and bunch varieties cure on the which was granted in 1864. It has associated Law and Medical stem and furnish nutritive food throughout the year. Before the Schools. The Chamberlin Astronomical Observatory, with a 20. plains were fenced, large herds drifted to the south during the inch aperture telescope, is part of its equipnient. winter; but sufficient hay and alfalfa are now cut to feed the cattle

(W. F. S.) during the storms, which at longest are brief. As the industry has grown, laws have been enacted concerning branding, herding, Colorado Springs, capital of El Paso county, and protection from disease ; and a State Board of Inspectors has

Colorado, U.S.A. It is situated near the centre of the state, been formed. In 1884 the number of cattle was given as 1,005,000, and the number of sheep as 1,497,000. In 1899 the number was

upon the high plains near the base of the Rocky Moun as follows: cattle, 754,039; sheep, 930,839 ; horses, 194,923 ; and

tains, on Fontaine qui Bouille river, at the mouth of mules, 7480. The total assessed valuation was $11,627,730, the Monument creek, in 38° 50' N. lat. and 101° 49' W. long., at assessment being about one-third of the market value. Wool in an altitude of 5985 feet. Its situation is fine, commanding 1898 averaged seven pounds per fleece, the total clip yielding $840,000. The total value of cattle slaughtered in the packing

a superb view of the mountains, whose culminating point, houses in 1898 was $3,168,000. The value of the dairy product

Pike's Peak, rises to a height of 14,108 feet, or more than in the same year was $13, 267,849.

8000 feet above the city. It is entered by five railways : Manufactures.—Since 1888 there has been a considerable growth the Denver and Rio Grande; the Atchison, Topeka, and of manufacturing. There are 18 smelters and reduction plants in

Santa Fé; the Colorado and Southern ; the Chicago, Rock the State, situated mainly at Denver, Leadville, Durango, and at Pueblo, where there are also blast-furnaces, a steel plant, and

Island, and Pacific; and the Colorado Midland. It is the rolling mills. The most improved methods of treating ore are site of Colorado College, which in 1899 had a faculty used. The cyanide process, introduced in 1890, is now one of the numberiny thirty-three, and was attended by 335 students. most important factors in the treatment of low-grade and refractory gold and silver ores. The improved dioxide cyanide process was

Colorado Springs was founded in 1871, upon the conadopted in 1895. One million barrels of flour were produced during

struction of the Denver and Rio Grande Railway, and 1899, the fifty mills having a capacity of 2,000,000 per annum.

has had a rapid growth. In its earlier years this was Cotton and paper manufactures are carried on in the vicinity of due to the beauty of its situation and its reputation Denver. According to the United States' Census of 1900, there were in the State 1792 manufacturing establishments (excluding

as a health resort for consumptives. In later years the 1778 classified as hand trades, and 292 others, with a product of

development of the gold mines at Cripple Creek has less than $500 each). They had a total capital of $59,515,279, an

given it importance as a supply-point for this great average number of 19,948 wage-earners, and products valued at mining camp. Population (1880), 4226; (1890), 11,140; $91,639,495. This sum includes the value of the gold, silver, lead, (1900), 21,085, of whom 2300 were foreign - born and and copper smelted, which amounted to $44,625, 305. Of the other

875 negroes. products, iron and steel (valued at $6,108, 295), flouring and grist mill products (valued at $4,528,062), and foundry and machine shop products (valued at $3,986, 915), were the most important.

Colossæ, once the great city of South-West Phrygia, Railways.—The Denver Pacific, built from Cheyenne, reached was situated at an altitude of 1150 feet on rising ground on Denver in June 1870, and the Kansas Pacific in August of the same the left bank of the Lycus (Churuk Su), a tributary of the year. Then followed the Denver and Rio Grande, to which the

Mæander, at the upper end of a narrow gorge 21 miles earlier development of the State is largely due. In 1886 the Colorado Midland started from Colorado Springs westwards, up the

long, through which the river runs between cliffs from 50 Ute Pass, and through the South Park to Leadville, and then over to 60 feet high. It stood on the gizat trade route from the Continental Divide to Aspen and Glenwood Springs ; it has Sardis to Celænæ and Iconium, and was a large, prosperright of way over the Denver and Rio Grande line to Grand Junction,

ous, and populous city (Herod. vii. 30; Xenophon, Anal. there connecting with the Rio Grande Western for Salt Lake City and Ogden, and the Pacific Coast. The Colorado and Southern,

i. 2, § 6), until its prosperity was ruined by the foundaconnecting Colorado with the south, has become an important

tion of Laodicea in a more advantageous position. The system. In 1900 there were fifteen railways, with 1685 miles, in town was celebrated for its wool, which was dyed a purple operation. The assessment on railways, tramways, telephones, and colour called colossinus. Colossæ was the seat of an early telegraphs was $35,533,586. Finances. The assessed valuation in real and personal property

Christian Church, possibly founded by Epaphras, to which in 1876 was $44,130,205 ; in 1899 the total assessed valuation of

St Paul addressed an epistle. For some centuries it conall properties was $203,861,746 ; but this was regarded by the tinued to prosper, but during the 7th and 8th centuries it State Board as too low, and 5 per cent increase was recommended. was gradually deserted under pressure of the Arab invaTaxes were levied in 1899 to the amount of $4,688,458. The total State debt in 1899 was $2,584,443. The cash in the trea

sions. Its place was taken by Khona (Khonas)—a strong sury and uncollected taxes, $849, 275, leaving a balance of indebt

fortress on a rugged spur of Mt. Kadmus, 3 miles to the edness of $1,735,167. The total deposits in the 36 national south, which became a place of importance during the banks on 13th February 1900, was $15,802,863.

wars between the Byzantines and Turks, and was the Education.—Of the public lands, 3, 715,555 acres were granted birthplace of the historian, Vicetas Khoniates... The worfor the support of schools, 46,080 acres for the University, and 90,000 acres for the Agricultural College. In 1900 the number of

ship of angels alluded to by St Paul (Col. ii. 18), and persons of school age (5 to 20 years inclusive) was 160,531. The condemned in the 4th century by a council at Laodicea, amount apportioned to the various school districts for 1900 was

reappears in the later worship of St Michael, in whose $62,577, and the total value of all school properties was $6,495,850. honour a celebrated church, destroyed by the Seljüks in The salaries paid to the teachers in the public schools during 1899 and 1900 amounted to $1,423,680. Graded schools are found

the 12th century, was built on the right bank of the throughout the State, and high schools in all the larger towns. Lycus (Ramsay, Cities and Bishoprics of Phrygia, vol. i. The State institutions are : the University of Colorado, at Boulder ; 1895).






enemy or prey respectively. The animal is not hidden

from view by becoming indistinguishable from its backMHE scope of this article includes the uses of colour in ground, as in the cases of General Resemblance, but it is

the struggle for existence among animals and in their mistaken for some well-known object. sexual relationships, but not the physiological uses of In seeking the interpretation of these most interesting coloured pigments or the discussion of pigments of un- and elaborate adaptations, attempts have been made along certain meaning

two lines. First, it is sought to explain the effect as a Use of Colour for Concealment.Cryptic Colouring is result of the direct influence of the environment upon the by far the commonest use of colour in the struggle for individual (Buffon), or by the inherited effects of effort and existence. It is employed for the purpose of attack the use and disuse of parts (Lamarck). Second, natural (Aggressive Resemblance or Anticryptic Colouring) as well as selection is believed to have produced the result, and afterof defence (Protective Resemblance or Procryptic Colouring). wards maintained it by the survival of the best concealed The fact that the same method, concealment, may be used in each generation. The former suggestions break down both for attack and defence has been well explained by when the complex nature of numerous Special Resemblances Belt (The Naturalist in Nicaragua, London, 1888), who is appreciated. Thus the arrangement of colours of many suggests as an illustration the rapidity of movement which kinds into an appropriate pattern requires the co-operation is also made use of by both pursuer and pursued, which is of a suitable shape and the rigidly exact adoption of a similarly raised to a maximum in both by the gradual certain elaborate attitude. The latter is instinctive, and dying out of the slowest through a series of generations. thus depends on the central nervous system. The cryptic Cryptic colouring is commonly associated with other aids effect is due to the exact co-operation of all these factors ; in the struggle for life. Thus well-concealed mammals and in the present state of science the only possible hope and birds, when discovered, will generally endeavour to of an interpretation lies in the theory of natural selection, escape by speed, and will often attempt to defend them

which can


every variation which tends selves actively. On the other hand, small animals which towards survival. A few of the chief types of methods by have no means of active defence, such as large numbers of which concealment is effected may be briefly described. insects, frequently depend upon concealment alone. Pro

The colours of large numbers of Vertebrate animals are tective Resemblance is far commoner among animals than darkest on the back, and become gradually lighter on the Aggressive Resemblance, in correspondence with the fact sides, passing into white on the belly. Abbot H. Thayer that predaceous forms are as a rule much larger and (The Auk, vol. xiii., 1896) has suggested that this gradation much less numerous than their prey. In the case of in- obliterates the appearance of solidity, which is due to sectivorous Vertebrata and their prey such differences exist shadow. The colour-harmony, which is also essential to in an exaggerated form. Cryptic colouring, whether used concealment, is produced because the back is of the same for defence or attack, may be either General or Special. tint as the environment (e.g., earth) bathed in the cold In General Resemblance the animal, in consequence of its blue-white of the sky, while the belly, being cold bluecolouring, produces the same effect as its environment, white bathed in shadow and yellow earth reflexions, but the conditions do not require any special adaptation produces the same effect. Thayer has made models in

( of shape and outline. General Resemblance is especially the Natural History Museums at London, Oxford, and common among the animals inhabiting some uniformly Cambridge) which support his interpretation in a very coloured expanse of the earth's surface, such as an ocean convincing manner. This method of neutralizing shadow or a desert.

In the former, animals of all shapes are for the purpose of concealment by increased lightness frequently protected by their transparent blue colour ; of tint was first suggested by E. B. Poulton in the case on the latter, equally diverse forms are defended by their of a larva (Trans. Ent. Soc. Lond., 1887, p. 294) and sandy appearance. The effect of a uniform appearance pupa (Trans. Ent. Soc. Lond., 1888, pp. 596, 597), may be produced by a combination of tints in startling but he did not appreciate the great importance of the contrast. Thus the black and white stripes of the zebra principle. In an analogous method an animal in front of blend together at a little distance, and “their proportion background of dark shadow may have part of its body is such as exactly to match the pale tint which arid obliterated by the existence of a dark tint, the remainder ground possesses when seen by moonlight” (Galton, South resembling, e.g., a part of a leaf (Müller, Zool. Jahr. J. Il'. Africa, London, 1889). Special Resemblance is far com- Spengel, Jena, 1886). This method of rendering invisible moner than General, and is the form which is usually met any part which would interfere with the resemblance is well with on the diversified surface of the earth, on the shores, known in Mimicry. A common aid to concealment is the and in shallow water, as well as on the floating masses of adoption by different individuals of two or more different Algæ on the surface of the ocean, such as the Sargasso appearances, each of which resembles some special object Sea. In these environments the cryptic colouring of to which an enemy is indifferent. Thus the leaf-like animals is usually aided by special modifications of shape, butterflies (Kallima) present various types of colour and and by the instinct which leads them to assume particular pattern on the under side of the wings, each of which attitudes. Complete stillness and the assumption of a closely resembles some well-known appearance presented certain attitude play an essential part in General Resem- by a dead leaf; and the common British Yellow Underblance on land; but in Special Resemblance the attitude is wing Moth (Tryphæna pronuba) is similarly polymorphic often highly specialized, and perhaps more important than on the upper side of its upper wings, which are exposed as any other element in the complex method by which con- it suddenly drops among dead leaves. Caterpillars and cealment is effected. In Special Resemblance the com- pupwe are also commonly Dimorphic, green and brown. bination of colouring, shape, and attitude is such as to Such differences as these extend the area which an produce a more or less exact resemblance to some one of enemy is compelled to search in order to make a living. the objects in the environment, such as a leaf or twig, a In many cases the cryptic colouring changes appropriately patch of lichen, or flake of bark. In all cases the resem- during the course of an individual life, either seasonally, blance is to some object which is of no interest to the as in the ptarmigan or Alpine hare, or, according as the

[ocr errors]

individual enters a new environment in the course of its similarity, just as Syncryptic Resemblance is produced by growth (such as larva, pupa, imago, &c.). In insects with static similarity. more than one brood in the year, Seasonal Dimorphism is Use of Colour for Warning and Signalling.—The use often seen, and the differences are sometimes appropriate of colour for the purpose of warning is the exact opposite to the altered condition of the environment as the seasons of the one which has been just described, its object being change. The causes of change in these and Arctic animals to render the animal conspicuous to its enemies, so that it are insufficiently worked out: in both sets there are observ- can be easily seen, well remembered, and avoided in future. ations or experiments which indicate changes from within Warning colours are associated with some quality or weapon the organism, merely following the seasons and not caused which renders the possessor unpleasant or dangerous, such by them, and other observations or experiments which as unpalatability, an evil odour, a sting, the poison-fang, prove that certain species are susceptible to the changing &e. The object being to warn an enemy off, these colours

c external influences. In certain species concealment is are also called Aposematic. Recognition markings, on effected by the use of adventitious objects, which are em- the other hand, are Episematic, assisting the individuals ployed as a covering. Examples of this Allocryptic of the same species to keep together when their safety defence are found in the tubes of the caddis worms depends upon numbers, or easily to follow each other to a (Phryganea), or the objects made use of by crabs of the place of safety, the young and inexperienced benefiting by genera Hyas, Stenorhynchus, &c. Such animals are con- the example of the older. Episematic characters are far less cealed in


environment. If sedentary, like the former common than Aposematic, and these than Cryptic; although, example, they are covered up with local materials; if as regards the latter comparison, the opposite impression is wandering, like the latter, they have the instinct to reclothe. generally produced from the very fact that concealment Allocryptic methods may also be used for aggressive pur- is so successfully attained. Warning or Aposematic Colours, poses, as the ant-lion larva, almost buried in sand, or the together with the qualities they indicate, depend, as a rule, large frog Ceratophrys, which covers its back with earth when for their very existence upon the abundance of palatable waiting for its prey. Another form of Allocryptic defence is food supplied by the animals with Cryptic colouring. Unfound in the use of the colour of the food in the digestive palatability, or even the possession of a sting, is not organs showing through the transparent body, and in certain sufficient defence unless there is enough food of another cases the adventitious colour may be dissolved in the blood kind to be obtained at the same time and place (Poulton, or secreted in superficial cells of the body : thus certain Proc. Zool. Soc., 1887, p. 191). Hence insects with Warninsects make use of the chlorophyll of their food (Poul- ing Colours are not seen in temperate countries except at ton, Proc, Roy. Soc. vol. liv. p. 417). The most perfect the time when insect life as a whole is most abundant; Cryptic powers are possessed by those animals in which and in warmer countries, with well-marked wet and dry the individuals can change their colours into any tint seasons, it will probably be found that Warning Colours are which would be appropriate to a normal environment. proportionately less developed in the latter. In many This power is widely prevalent in Fish, and also occurs in species of African butterflies belonging to the genus Amphibia and Reptilia (the chameleon affording a well- Junonia (including Precis) the wet-season broods are known example). Analogous powers exist in certain distinguished by the more or less conspicuous under sides Crustacea and Cephalopoda. All these rapid changes of of the wings, those of the dry season being highly cryptic. colour are due to changes in shape or position of superficial Warning Colours are, like Cryptic, assisted by special pigment cells controlled by the nervous system. That the adaptations of the body-form, and especially by movelatter is itself stimulated by light through the medium of ments which assist to render the colour as conspicuous as the eye and optic nerve has been proved in many cases. possible. On this account animals with Warning Colours Animals with a short life-history passed in a single en- generally move or fly slowly, and it is the rule in buttervironment, which, however, may be very different in the flies that the Warning patterns are similar on both upper case of different individuals, may have a different form of and under sides of the wings. Many animals, when Variable Cryptic Colouring, namely, the power of adapting attacked or disturbed, “sham death” (as it is commonly their colour once for all (many pupa), or once or twice (many but wrongly described), falling motionless to the ground. larvæ). In these cases the effect appears to be produced In the case of well-concealed animals this instinct gives through the nervous system, although the stimulus of them a second chance of escape in the earth or among light probably acts on the skin and not through the eyes. the leaves, &c., when they have been once detected; animals Particoloured surfaces do not produce particoloured pupa, with Warning Colours are, on the other hand, enabled to probably because the antagonistic stimuli neutralize each assume a position in which their characters are displayed other in the central nervous system which then disposes to the full (Portschinski, Lepidopterorum Rossiæ Biologia, the superficial colours so that a neutral or intermediate St. Petersburg, 1890, plate i. figs. 16, 17). In both effect is produced over the whole surface (Poulton, Trans. cases a definite attitude is assumed, which is not that of Ent. Soc. Lond., 1892, p. 293). Cryptic colouring may

death. Other warning characters exist in addition to incidentally produce superficial resemblances between colouring : thus sound is made use of by the disturbed animals; thus desert forms concealed in the same way may Rattle-snake and the Indian Echis, &c. Large birds, gain a likeness to each other, and in the same way Special when attacked, often adopt a threatening attitude, Resemblances, e.g., to lichen, bark, grasses, pine-needles, accompanied by a terrifying sound. The Cobra warns &c., may sometimes lead to a tolerably close similarity an intruder chiefly by attitude and the dilation of the between the animals which are thus concealed. Such flattened neck, the effect being heightened in some likeness may be called Syncryptic or Common Protective species by the “spectacles.”

In such cases

we often (or Aggressive) Resemblance, and it is to be distinguished see the combination of Cryptic and Sematic methods, the from Mimicry and Common Warning Colours, in which the animal being concealed until disturbed, when it instantly likeness is not incidental but an end in itself. Syn- assumes an Aposematic attitude. The advantage to the cryptic Resemblances have much in common with those animal itself is clear: a poisonous snake gains nothing incidentally caused by functional adaptation, such as the by killing an animal it cannot eat; while the poison does mole-like forms produced in the burrowing Insectivora, not cause immediate death, and the enemy would have time Rodentia, and Marsupialia. Such likeness may be called to injure or destroy the snake. In the case of small unSyntechnic Resemblance, incidentally produced by dynamic palatable animals with Warning Colours the enemies would


[ocr errors]

only first become aware of the unpleasant quality by tasting education of young inexperienced enemies is facilitated. and often destroying their prey; but the species would Each species which falls into a group with Common Warngain by the experience thus conveyed, even though the ing (Synaposematic) Colours contributes to save the lives individual might suffer. An insect-eating animal does of the other members. It is sufficiently obvious that the not come into the world with knowledge : it has to be amount of learning and remembering, and consequently educated by experience, and Warning Colours enable this of injury and loss of life involved in the process, are education as to what to avoid to be gained by a small reduced when many species in one place possess the same instead of a large waste of life. Furthermore, great | Aposematic colouring, instead of each exhibiting a different tenacity of life is usually possessed by animals with Warn- danger-signal.” These resemblances are often described ing Colours. The tissues of Aposematic insects generally as “Müllerian Mimicry,” as distinguished from true or possess great elasticity and power of resistance, so that “Batesian Mimicry” described in the next section. Similar large numbers of individuals can recover after very severe Synaposematic resemblances between the specially protected treatment.

groups of butterflies were afterwards shown to exist in The brilliant Warning Colours of many caterpillars tropical Asia, the East Indian Islands, and Polynesia by attracted the attention of Darwin when he was thinking F. Moore (Proc. Zool. Soc., 1883, p. 201), and in Africa over his hypothesis of sexual selection, and he wrote to by E. B. Poulton (Report Brit. Assoc., 1897, p. 688). R. Wallace on the subject (Darwin, Life and Letters, London, Meldola (Ann. and May. Nat. Hist. x., 1882, p. 417) 1887, vol. iii. p. 93). Wallace, in reply, suggested their first pointed out and explained in the same manner the interpretation as Warning Colours, a suggestion since remarkable general uniformity of colour and pattern verified by experiment (Proc. Ent. Soc. Lond., 1867, which runs through so many species of each of the disp. lxxx; Trans. Ent. Soc. Lond., 1869, pp. 21 and 27). tasteful groups of butterflies; while, still later, Poulton Although animals with Warning Colours are probably but (Proc. Zool. Soc., 1887, p. 191) similarly extended the little attacked by the ordinary enemies of their class, interpretation to the Synaposematic resemblances between they have special enemies which keep the numbers down animals of all kinds in the same country. Thus, for to the average.

Thus the cuckoo appears to be an insect- example, longitudinal or circular bands of the same ivorous bird which will freely devour conspicuously strongly contrasted colours are found in species of many coloured unpalatable larvæ. The effect of the Warning groups with distant affinities. Colours of caterpillars is often intensified by gregarious Certain animals, especially the Crustacea, make use of habits. Another Aposematic use of colours and structures the special defence and Warning Colours of other animals. is to divert attention from the vital parts, and thus give Thus the English Hermit-crab, Pagurus bernhardus, comthe animal attacked an extra chance of escape. The large, monly carries the Sea-anemone, Sagartia parasitica, on its conspicuous, easily torn wings of butterflies and moths act shell; while another English species, Payurus prideauxii, in this way, as is found by the abundance of individuals inhabits a shell which is invariably clothed by the flattened which may be captured with notches bitten symmetrically Adamsia palliata. out of both wings when they were in contact.

The white patch near the tail which is frequently seen spots and “tails”

so common on the hinder part of the in the gregarious Ungulates, and is often rendered hind wing, and the conspicuous apex so frequently seen on conspicuous by adjacent black markings, probably assists the fore wing, probably have this meaning. Their position the individuals in keeping together; and appearances corresponds to the parts which are most often found to be with probably the same interpretation are found in notched. In some cases (e.g., many Lycænidæ) the “ tail”

The white upturned tail of the rabbit and eye-spot combine to suggest the appearance of a head is probably of use in enabling the individuals to follow with antennæ at the posterior end of the butterfly, the each other readily. The difference between a typical deception being aided by movements of the hind wings. Aposematic character appealing to enemies, and EpiseThe flat-topped “tussocks” of hair on many caterpillars matic intended for other individuals of the same species, look like conspicuous fleshy projections of the body, and is well seen when we compare such examples as (1) they are held prominently when the larva is attacked. If the huge banner-like white tail, conspicuously conseized, the “tussock comes out, and the enemy is greatly trasted with the black or black and white body, by inconvenienced by the fine branched hairs. The tails of which the slow-moving skunk warns enemies of its power lizards, which easily break off, are to be similarly explained, of emitting an intolerably offensive odour; (2) the small the attention of the pursuer being probably still further upturned white tail of the rabbit, only seen when it is diverted by the extremely active movements of the likely to be of use and when the owner is moving, and, if amputated member. Certain crabs similarly throw off pursued, very rapidly moving, towards safety. their claws when attacked, and the claws continue to snap Mimicry, or Pseudo-sematic Colours.—The fact that most actively. The tail of the dormouse, which casily animals with distant affinities may more or less closely comes off, and the extremely bushy tail of the squirrel, are resemble each other was observed long before the existing probably of use in the same manner. Animals with explanation was possible. Its recognition is implied in Warning Colours often tend to resemble each other a number of insect names with the termination -formis, superficially. This fact was first pointed out by H. W. usually given to species of various Orders which more or Bates in his paper on the Theory of Mimicry (Truns. less closely resemble the stinging Hymenoptera. The Linn. Soc. vol. xxiii., 1862, p. 495). He showed that the usefulness of the resemblance was suggested in Kirby and conspicuous, presumably unpalatable, tropical American Spence's Introduction to Entomology, London, 1817, vol. butterflies, belonging to very different groups, which are ii. p. 223. H. W. Bates (Trans. Linn. Soc. vol. xxiii. mimicked by others, also tend to resemble each other, the 1862, 1) 495) first proposed an explanation of Mimicry based likeness being often remarkably exact. These resemblances on the theory of Natural Selection. He supposed that were not explained by his theory of Mimicry, and he could every step in the formation and gradual improvement of only suppose that they had been produced by the direct the likeness occurred in consequence of its usefulness in influence of a common environment. The problem was the struggle for life. The subject is of additional interest, solved in 1879 by Fritz Müller (see Proc. Ent. Soc. Lond., inasmuch as it was one of the first attempts to apply the 1879, p. xx), who suggested that life is saved by this theory of Natural Selection to a large class of phenomena resemblance between Warning Colours, inasmuch as the up to that time well known but unexplained. Numerous

The eye

many birds.


examples of Mimicry among tropical American butterflies consequence of advantage in the struggle ; also by the were discussed by Bates in his paper; and in 1866 A. R. operation of Sexual Selection. Wallace extended the hypothesis to the butterflies of the It is proposed, in conclusion, to give an account of the tropical East (Trans. Linn. Soc. vol. xxv., 1866, p. 19); broad aspects of Mimicry, and attempt a brief discussion Roland Trimen (Trans. Linn. Soc. vol. xxvi., 1870, of the theories of origin of each class of facts (see Poulton, p. 497) to those of Africa in 1870. The term Mimicry is Linn. Soc. Journ. Zool., 1898, p. 558). It will be found that

. used in various senses. It is often extended, as indeed it in many cases the argument here made use of applies equally was by Bates, to include all the superficial resemblances to the origin of Cryptic and Sematic Colours. The relationbetween animals and any part of their environment. ship between these classes has been explained : Mimicry Wallace, however, separated the Cryptic Resemblances is, as Wallace has stated (Darwinism, London, 1889), already described, and the majority of naturalists have merely “an exceptional form of protective resemblance." followed this convenient arrangement. In Cryptic Resem- Now, protective (cryptic) resemblance cannot be explained blance an animal resembles some object of no interest to on any of the lines suggested above, except natural its enemy (or prey), and in so doing is concealed ; in selection; even sexual selection fails, because cryptic Mimicry an animal resembles some other animal which is resemblance is especially common in the immature stages specially disliked by its enemy, or some object which is of insect life. But it would be unreasonable to explain specially attractive to its prey, and in so doing becomes Mimetic Resemblance by one set of principles and Cryptic conspicuous. Some naturalists have considered Mimicry by another and totally different set. Again, it may be to include all superficial likenesses between animals, but plausible to explain the mimicry of one butterfly for such a classification would group together resemblances another on one of the suggested lines, but the resemblance which have widely different uses. (1) The resemblance of a fly or moth to a wasp is by no means so easy, and of a mollusc to the coral on which it lives, or an external here selection would be generally conceded; yet the appeal parasite to the hair or skin of its host, would be Pro- to antagonistic principles to explain such closely related cryptic; (2) that between moths which resemble lichen, cases would only be justified by much direct evidence. Syncryptic ; (3) between distasteful insects, Synaposematic; Furthermore, the mimetic resemblances between butter(4) between the Insectivor mole and the Rodent mole-rat, flies are not haphazard, but the models almost invariably Syntechnic; (5) the essential element in Mimicry is that it is belong only to certain sub-families, the Danainc and afalse warning (Pseud-aposematic) or false recognition (Pseud- Acraeinæ in all the warmer parts of the world, and, in episematic) character. Some have considered that Mimicry tropical America, the Ithomiince and Heliconince as well

. indicates resemblance to a moving object; but apart from These groups have the characteristics of Aposematic species, the non-mimetic likenesses between animals classified above, and no theory but natural selection explains their inthere are ordinary Cryptic Resemblances to drifting leaves, variable occurrence as models wherever they exist. It is swaying bits of twig, &c., while truly Mimetic Resemblances impossible to suggest, except by natural selection, any are often specially adapted for the attitude of rest. Many explanation of the fact that mimetic resemblances are use the term Mimicry to include Synaposematic as well as confined to changes which produce or strengthen a superPseudo-sematic . Resemblances, calling the former “ Müller- ficial likeness. Very deep-seated changes are generally ian,” the latter “Batesian," Mimicry. The objection to involved, inasmuch as the appropriate instincts as to this grouping is that it takes little account of the decep- attitude, &c., are as important as colour and marking. tive element which is essential in Mimicry. In Syn- The same conclusion is reached when we analyse the nature aposematic colouring the warning is genuine, in Pseud- of mimetic resemblance and realize how complex it really aposematic it is a sham. The term Mimicry has led to is, being made up of colours, both pigmentary and strucmuch misunderstanding from the fact that in ordinary tural, pattern, form, attitude, and movement. A plausible speech it implies deliberate imitation. The production of interpretation of colour may be wildly improbable when Mimicry in an individual animal has no more to do with applied to some other element, and there is no explanation consciousness or “taking thought” than any of the other except natural selection which can explain all these processes of growth. Protective Mimicry is here defined as elements. The appeal to the direct action of local conditions an advantageous and superficial resemblance of one animal in common often breaks down upon the slightest investito another, which latter is specially defended so as to be gation, the difference in habits between mimic and model disliked or feared by the majority of enemies of the groups in the same locality causing the most complete divergence in to which both belong—a resemblance which appeals to the their conditions of life. Thus many insects produced from sense of sight, sometimes to that of hearing, and rarely to burrowing larvæ mimic those whose larvæ live in the open. smell, but does not extend to deep-seated characters except Mimetic resemblance is far commoner in the female than in when the superficial likeness is affected by them. Mutatis the male, a fact readily explicable by selection, as suggested mutandis this definition will apply to Aggressive (Pseud-by Wallace, for the female is compelled to fly more slowly episematic) Resemblance. The conditions under which and to expose itself while laying eggs, and hence a resemMimicry occurs have been stated by Wallace :-“(1) that blance to the slow-flying freely exposed models is especially the imitative species occur in the same area and occupy

the advantageous. The facts that mimetic species occur in the same station as the imitated; (2) that the imitators are same locality, fly at the same time of the year as their always the more defenceless ; (3) that the imitators are models, and are day-flying species even though they may always less numerous in individuals ; (4) that the imitators belong to nocturnal groups, are also more or less difficult differ from the bulk of their allies ; (5) that the imitation, to explain except on the theory of natural selection, and so however minute, external and visible only, never extend- also is the fact that mimetic resemblance is produced in the ing to internal characters or to such as do not affect the most varied manner. A spider resembles its model, an external appearance.” It is obvious that conditions 2 and ant, by a modification of its body-form into a superficial 3 do not hold in the case of Müllerian Mimicry. Mimicry resemblance, and by holding one pair of legs to represent has been explained, independently of Natural Selection, by antennæ; certain bugs (Hemiptera) and beetles have also the supposition that it is the common expression of the gained a shape unusual in their respective groups, a direct action of common causes, such as climate, food, &c.; shape which superficially resembles an ant; a Locustid also by the supposition of independent lines of evolution (Myrmecophana has the shape of an ant painted, as it

) leading to the same result without any selective action in were, on its body, all other parts resembling the back

« EelmineJätka »