the State. Melons from Rocky Ford and peaches from Mesa county are shipped to the east, and in small quantities to Europe. The report for 1898 shows that the staple grains gave the following yield in bushels: wheat, 6,729,565; corn, 3,113,892; barley, 353,952; oats, 3,063,191; rye, 47,484. The hay product was 1,760,728 tons, and potatoes 2,564,331 bushels. The total value of these products was estimated at $17,349,251, as against $3,047,750 in 1882. It has been discovered by experiments conducted by the United States Government, through the Agricultural College, that the soil along the South Platte, the Arkansas and Grand rivers, and also in the San Luis Valley, is adapted for the cultivation of sugar beets, the average crop being 16 tons to the acre, and the proportion of saccharine matter unusually large. Sugar factories have been built at Grand Junction, Rocky Ford, and Sugar City; the first with a daily capacity of 3500 tons, and the others of 7500 tons. Stock-raising has always played an important part in the development of the State. The native grasses are especially adapted for fodder. The grama, buffalo, and bunch varieties cure on the stem and furnish nutritive food throughout the year. Before the plains were fenced, large herds drifted to the south during the winter; but sufficient hay and alfalfa are now cut to feed the cattle during the storms, which at longest are brief. As the industry has grown, laws have been enacted concerning branding, herding, and protection from disease; and a State Board of Inspectors has 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 as follows: cattle, 754,039; sheep, 930,839; horses, 194, 923; and mules, 7480. The total assessed valuation was $11,627,730, the assessment being about one-third of the market value. Wool in 1898 averaged seven pounds per fleece, the total clip yielding $840,000. The total value of cattle slaughtered in the packing houses in 1898 was $3,168,000. The value of the dairy product in the same year was $13,267,849.

Manufactures.-Since 1888 there has been a considerable growth of manufacturing. There are 18 smelters and reduction plants in the State, situated mainly at Denver, Leadville, Durango, and at Pueblo, where there are also blast-furnaces, a steel plant, and rolling mills. The most improved methods of treating ore are used. The cyanide process, introduced in 1890, is now one of the most important factors in the treatment of low-grade and refractory gold and silver ores. The improved dioxide cyanide process was adopted in 1895. One million barrels of flour were produced during 1899, the fifty mills having a capacity of 2,000,000 per annum. Cotton and paper manufactures are carried on in the vicinity of Denver. According to the United States' Census of 1900, there were in the State 1792 manufacturing establishments (excluding 1778 classified as hand trades, and 292 others, with a product of less than $500 each). They had a total capital of $59,515,279, an average number of 19,948 wage-earners, and products valued at $91,639,495. This sum includes the value of the gold, silver, lead, and copper smelted, which amounted to $44,625,305. Of the other 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.

Railways.-The Denver Pacific, built from Cheyenne, reached Denver in June 1870, and the Kansas Pacific in August of the same year. Then followed the Denver and Rio Grande, to which the earlier development of the State is largely due. In 1886 the Colorado Midland started from Colorado Springs westwards, up the Ute Pass, and through the South Park to Leadville, and then over the Continental Divide to Aspen and Glenwood Springs; it has right of way over the Denver and Rio Grande line to Grand Junction, there connecting with the Rio Grande Western for Salt Lake City and Ogden, and the Pacific Coast. The Colorado and Southern, connecting Colorado with the south, has become an important system. In 1900 there were fifteen railways, with 4685 miles, in operation. The assessment on railways, tramways, telephones, and telegraphs was $35,533,586.

Finances.-The assessed valuation in real and personal property in 1876 was $44,130,205; in 1899 the total assessed valuation of all properties was $203,861,746; but this was regarded by the State Board as too low, and 5 per cent. increase was recommended. Taxes 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 treasury and uncollected taxes, $849,275, leaving a balance of indebtedness of $1,735,167. The total deposits in the 36 national banks on 13th February 1900, was $45,802,863.

Education. Of the public lands, 3,715,555 acres were granted for the support of schools, 46,080 acres for the University, and 90,000 acres for the Agricultural College. In 1900 the number of persons of school age (5 to 20 years inclusive) was 160,531. The amount apportioned to the various school districts for 1900 was $62,577, and the total value of all school properties was $6,495,850. The salaries paid to the teachers in the public schools during 1899 and 1900 amounted to $1,423,680. Graded schools are found throughout the State, and high schools in all the larger towns. The State institutions are: the University of Colorado, at Boulder;

the School of Mines, at Golden: the Agricultural College, at Fort Collins; the Normal School, at Greeley; the School for the Deaf and Blind, at Colorado Springs; the Industrial School for boys, at Golden, and for girls at Aurora. These are supported by a mill tax, and special appropriations. The State University has an annual income of $70,000, and a library of 19,000 volumes; the School of Mines, an income of $37,000; and the Normal School an income of $32,000, and a library of 10,000 volumes. The Agricultural College has an income of $65,500, of which $23,000 is from the United States Government. Experiment stations are conducted in connexion with the college at Fort Collins, Rocky Ford, and Cheyenne Wells. There are two institutions for higher education on an independent foundation. Colorado College, at Colorado Springs, is the oldest existing college in the State. Its property in equipment and endowment is $1,500,000, and it has a library of 30,000 volumes. The University of Denver, under Methodist control, is an outgrowth of the Colorado Seminary, the charter of which was granted in 1864. It has associated Law and Medical Schools. The Chamberlin Astronomical Observatory, with a 20. inch aperture telescope, is part of its equipment.

(W. F. S.)

Colorado Springs, capital of El Paso county, Colorado, U.S.A. It is situated near the centre of the state, upon the high plains near the base of the Rocky Moun tains, on Fontaine qui Bouille river, at the mouth of Monument creek, in 38° 50′ N. lat. and 104° 49′ W. long., at an altitude of 5985 feet. Its situation is fine, commanding a superb view of the mountains, whose culminating point, Pike's Peak, rises to a height of 14,108 feet, or more than 8000 feet above the city. It is entered by five railways: the Denver and Rio Grande; the Atchison, Topeka, and Santa Fé; the Colorado and Southern; the Chicago, Rock Island, and Pacific; and the Colorado Midland. It is the site of Colorado College, which in 1899 had a faculty numbering thirty-three, and was attended by 335 students. Colorado Springs was founded in 1871, upon the construction of the Denver and Rio Grande Railway, and has had a rapid growth. In its earlier years this was due to the beauty of its situation and its reputation as a health resort for consumptives. In later years the development of the gold mines at Cripple Creek has given it importance as a supply-point for this great mining camp. Population (1880), 4226; (1890), 11,140; (1900), 21,085, of whom 2300 were foreign-born and 875 negroes.

Colossæ, once the great city of South-West Phrygia, was situated at an altitude of 1150 feet on rising ground on the left bank of the Lycus (Churuk Su), a tributary of the Mæander, at the upper end of a narrow gorge 2 miles long, through which the river runs between cliffs from 50 to 60 feet high. It stood on the great trade route from Sardis to Celænæ and Iconium, and was a large, prosperous, and populous city (Herod. vii. 30; Xenophon, Anal. i. 2, § 6), until its prosperity was ruined by the foundation of Laodicea in a more advantageous position. The town was celebrated for its wool, which was dyed a purple colour called colossinus. Colossæ was the seat of an early Christian Church, possibly founded by Epaphras, to which St Paul addressed an epistle. For some centuries it continued to prosper, but during the 7th and 8th centuries it was gradually deserted under pressure of the Arab invasions. Its place was taken by Khonæ (Khonas)—a strong fortress on a rugged spur of Mt. Kadmus, 3 miles to the south, which became a place of importance during the wars between the Byzantines and Turks, and was the birthplace of the historian, Nicetas Khoniates. The wor

ship of angels alluded to by St Paul (Col. ii. 18), and condemned in the 4th century by a council at Laodicea, reappears in the later worship of St Michael, in whose honour a celebrated church, destroyed by the Seljuks in the 12th century, was built on the right bank of the Lycus (Ramsay, Cities and Bishoprics of Phrygia, vol. i. 1895).

S. III. 19

THE

1. BIONOMICS.

HE scope of this article includes the uses of colour in the struggle for existence among animals and in their sexual relationships, but not the physiological uses of coloured pigments or the discussion of pigments of uncertain meaning.

Use of Colour for Concealment.-Cryptic Colouring is by far the commonest use of colour in the struggle for existence. It is employed for the purpose of attack (Aggressive Resemblance or Anticryptic Colouring) as well as of defence (Protective Resemblance or Procryptic Colouring). The fact that the same method, concealment, may be used both for attack and defence has been well explained by Belt (The Naturalist in Nicaragua, London, 1888), who suggests as an illustration the rapidity of movement which is also made use of by both pursuer and pursued, which is similarly raised to a maximum in both by the gradual dying out of the slowest through a series of generations. Cryptic colouring is commonly associated with other aids in the struggle for life. Thus well-concealed mammals and birds, when discovered, will generally endeavour to escape by speed, and will often attempt to defend themselves actively. On the other hand, small animals which have no means of active defence, such as large numbers of insects, frequently depend upon concealment alone. Protective Resemblance is far commoner among animals than Aggressive Resemblance, in correspondence with the fact that predaceous forms are as a rule much larger and much less numerous than their prey. In the case of insectivorous Vertebrata and their prey such differences exist in an exaggerated form. Cryptic colouring, whether used for defence or attack, may be either General or Special. In General Resemblance the animal, in consequence of its colouring, produces the same effect as its environment, but the conditions do not require any special adaptation of shape and outline. General Resemblance is especially common among the animals inhabiting some uniformly coloured expanse of the earth's surface, such as an ocean or a desert. In the former, animals of all shapes are frequently protected by their transparent blue colour; on the latter, equally diverse forms are defended by their sandy appearance. The effect of a uniform appearance may be produced by a combination of tints in startling contrast. Thus the black and white stripes of the zebra blend together at a little distance, and "their proportion is such as exactly to match the pale tint which arid ground possesses when seen by moonlight" (Galton, South Africa, London, 1889). Special Resemblance is far commoner than General, and is the form which is usually met with on the diversified surface of the earth, on the shores, and in shallow water, as well as on the floating masses of Algae on the surface of the ocean, such as the Sargasso Sea. In these environments the cryptic colouring of animals is usually aided by special modifications of shape, and by the instinct which leads them to assume particular attitudes. Complete stillness and the assumption of a certain attitude play an essential part in General Resemblance on land; but in Special Resemblance the attitude is often highly specialized, and perhaps more important than any other element in the complex method by which concealment is effected. In Special Resemblance the combination of colouring, shape, and attitude is such as to produce a more or less exact resemblance to some one of the objects in the environment, such as a leaf or twig, a patch of lichen, or flake of bark. In all cases the resemblance is to some object which is of no interest to the

enemy or prey respectively. The animal is not hidden from view by becoming indistinguishable from its background, as in the cases of General Resemblance, but it is mistaken for some well-known object.

In seeking the interpretation of these most interesting and elaborate adaptations, attempts have been made along two lines. First, it is sought to explain the effect as a result of the direct influence of the environment upon the individual (Buffon), or by the inherited effects of effort and the use and disuse of parts (Lamarck). Second, natural selection is believed to have produced the result, and afterwards maintained it by the survival of the best concealed in each generation. The former suggestions break down when the complex nature of numerous Special Resemblances is appreciated. Thus the arrangement of colours of many kinds into an appropriate pattern requires the co-operation of a suitable shape and the rigidly exact adoption of a certain elaborate attitude. The latter is instinctive, and thus depends on the central nervous system. The cryptic effect is due to the exact co-operation of all these factors; and in the present state of science the only possible hope of an interpretation lies in the theory of natural selection, which can accumulate any and every variation which tends towards survival. A few of the chief types of methods by which concealment is effected may be briefly described. The colours of large numbers of Vertebrate animals are darkest on the back, and become gradually lighter on the sides, passing into white on the belly. Abbot H. Thayer (The Auk, vol. xiii., 1896) has suggested that this gradation obliterates the appearance of solidity, which is due to shadow. The colour-harmony, which is also essential to concealment, is produced because the back is of the same tint as the environment (e.g., earth) bathed in the cold blue-white of the sky, while the belly, being cold bluewhite bathed in shadow and yellow earth reflexions, produces the same effect. Thayer has made models (in the Natural History Museums at London, Oxford, and Cambridge) which support his interpretation in a very convincing manner. This method of neutralizing shadow for the purpose of concealment by increased lightness of tint was first suggested by E. B. Poulton in the case of a larva (Trans. Ent. Soc. Lond., 1887, p. 294) and a pupa (Trans. Ent. Soc. Lond., 1888, pp. 596, 597), but he did not appreciate the great importance of the principle. In an analogous method an animal in front of a background of dark shadow may have part of its body obliterated by the existence of a dark tint, the remainder resembling, e.g., a part of a leaf (Müller, Zool. Jahr. J. W. Spengel, Jena, 1886). This method of rendering invisible any part which would interfere with the resemblance is well known in Mimicry. A common aid to concealment is the adoption by different individuals of two or more different appearances, each of which resembles some special object to which an enemy is indifferent. Thus the leaf-like butterflies (Kallima) present various types of colour and pattern on the under side of the wings, each of which closely resembles some well-known appearance presented by a dead leaf; and the common British Yellow Underwing Moth (Tryphaena pronuba) is similarly polymorphic on the upper side of its upper wings, which are exposed as it suddenly drops among dead leaves. Caterpillars and pupe are also commonly Dimorphic, green and brown. Such differences as these extend the area which an enemy is compelled to search in order to make a living. In many cases the cryptic colouring changes appropriately during the course of an individual life, either seasonally, as in the ptarmigan or Alpine hare, or, according as the

only first become aware of the unpleasant quality by tasting and often destroying their prey; but the species would gain by the experience thus conveyed, even though the individual might suffer. An insect-eating animal does not come into the world. with knowledge: it has to be educated by experience, and Warning Colours enable this. education as to what to avoid to be gained by a small instead of a large waste of life. Furthermore, great tenacity of life is usually possessed by animals with Warning Colours. The tissues of Aposematic insects generally possess great elasticity and power of resistance, so that large numbers of individuals can recover after very severe treatment.

The eye

The brilliant Warning Colours of many caterpillars attracted the attention of Darwin when he was thinking over his hypothesis of sexual selection, and he wrote to Wallace on the subject (Darwin, Life and Letters, London, 1887, vol. iii. p. 93). Wallace, in reply, suggested their interpretation as Warning Colours, a suggestion since verified by experiment (Proc. Ent. Soc. Lond., 1867, p. lxxx; Trans. Ent. Soc. Lond., 1869, pp. 21 and 27). Although animals with Warning Colours are probably but little attacked by the ordinary enemies of their class, they have special enemies which keep the numbers down to the average. Thus the cuckoo appears to be an insectivorous bird which will freely devour conspicuously coloured unpalatable larvæ. The effect of the Warning Colours of caterpillars is often intensified by gregarious habits. Another Aposematic use of colours and structures is to divert attention from the vital parts, and thus give the animal attacked an extra chance of escape. The large, conspicuous, easily torn wings of butterflies and moths act in this way, as is found by the abundance of individuals which may be captured with notches bitten symmetrically out of both wings when they were in contact. spots and "tails" so common on the hinder part of the hind wing, and the conspicuous apex so frequently seen on the fore wing, probably have this meaning. Their position corresponds to the parts which are most often found to be notched. In some cases (e.g., many Lycanida) the "tail" and eye-spot combine to suggest the appearance of a head with antennæ at the posterior end of the butterfly, the deception being aided by movements of the hind wings. The flat-topped "tussocks" of hair on many caterpillars look like conspicuous fleshy projections of the body, and they are held prominently when the larva is attacked. If seized, the "tussock "" comes out, and the enemy is greatly inconvenienced by the fine branched hairs. The tails of lizards, which easily break off, are to be similarly explained, the attention of the pursuer being probably still further diverted by the extremely active movements of the amputated member. Certain crabs similarly throw off their claws when attacked, and the claws continue to snap most actively. The tail of the dormouse, which easily comes off, and the extremely bushy tail of the squirrel, are probably of use in the same manner. Animals with Warning Colours often tend to resemble each other superficially. This fact was first pointed out by H. W. Bates in his paper on the Theory of Mimicry (Trans. Linn. Soc. vol. xxiii., 1862, p. 495). He showed that the conspicuous, presumably unpalatable, tropical American butterflies, belonging to very different groups, which are mimicked by others, also tend to resemble each other, the likeness being often remarkably exact. These resemblances were not explained by his theory of Mimicry, and he could only suppose that they had been produced by the direct influence of a common environment. The problem was solved in 1879 by Fritz Müller (see Proc. Ent. Soc. Lond., 1879, p. xx), who suggested that life is saved by this resemblance between Warning Colours, inasmuch as the

education of young inexperienced enemies is facilitated. Each species which falls into a group with Common Warning (Synaposematic) Colours contributes to save the lives of the other members. It is sufficiently obvious that the amount of learning and remembering, and consequently of injury and loss of life involved in the process, are reduced when many species in one place possess the same Aposematic colouring, instead of each exhibiting a different danger-signal." These resemblances are often described as "Müllerian Mimicry," as distinguished from true or "Batesian Mimicry " described in the next section. Similar Synaposematic resemblances between the specially protected groups of butterflies were afterwards shown to exist in tropical Asia, the East Indian Islands, and Polynesia by F. Moore (Proc. Zool. Soc., 1883, p. 201), and in Africa by E. B. Poulton (Report Brit. Assoc., 1897, p. 688). R. Meldola (Ann. and Mag. Nat. Hist. x., 1882, p. 417) first pointed out and explained in the same manner the remarkable general uniformity of colour and pattern which runs through so many species of each of the distasteful groups of butterflies; while, still later, Poulton (Proc. Zool. Soc., 1887, p. 191) similarly extended the interpretation to the Synaposematic resemblances between animals of all kinds in the same country. Thus, for example, longitudinal or circular bands of the same strongly contrasted colours are found in species of many groups with distant affinities.

Certain animals, especially the Crustacea, make use of the special defence and Warning Colours of other animals. Thus the English Hermit-crab, Pagurus bernhardus, commonly carries the Sea-anemone, Sagartia parasitica, on its shell; while another English species, Pagurus prideauxii, inhabits a shell which is invariably clothed by the flattened Adamsia palliata.

The white patch near the tail which is frequently seen in the gregarious Ungulates, and is often rendered conspicuous by adjacent black markings, probably assists the individuals in keeping together; and appearances with probably the same interpretation are found in many birds. The white upturned tail of the rabbit

is probably of use in enabling the individuals to follow each other readily. The difference between a typical Aposematic character appealing to enemies, and Episematic intended for other individuals of the same species, is well seen when we compare such examples as (1) the huge banner-like white tail, conspicuously contrasted with the black or black and white body, by which the slow-moving skunk warns enemies of its power of emitting an intolerably offensive odour; (2) the small upturned white tail of the rabbit, only seen when it is likely to be of use and when the owner is moving, and, if pursued, very rapidly moving, towards safety.

Mimicry, or Pseudo-sematic Colours.-The fact that animals with distant affinities may more or less closely resemble each other was observed long before the existing explanation was possible. Its recognition is implied in a number of insect names with the termination formis, usually given to species of various Orders which more or less closely resemble the stinging Hymenoptera. The usefulness of the resemblance was suggested in Kirby and Spence's Introduction to Entomology, London, 1817, vol. ii. p. 223. H. W. Bates (Trans. Linn. Soc. vol. xxiii. 1862, p. 495) first proposed an explanation of Mimicry based on the theory of Natural Selection. He supposed that every step in the formation and gradual improvement of the likeness occurred in consequence of its usefulness in the struggle for life. The subject is of additional interest, inasmuch as it was one of the first attempts to apply the theory of Natural Selection to a large class of phenomena up to that time well known but unexplained. Numerous

Many

examples of Mimicry among tropical American butterflies were discussed by Bates in his paper; and in 1866 A. R. Wallace extended the hypothesis to the butterflies of the tropical East (Trans. Linn. Soc. vol. xxv., 1866, p. 19); Roland Trimen (Trans. Linn. Soc. vol. xxvi., 1870, p. 497) to those of Africa in 1870. The term Mimicry is used in various senses. It is often extended, as indeed it was by Bates, to include all the superficial resemblances between animals and any part of their environment. Wallace, however, separated the Cryptic Resemblances already described, and the majority of naturalists have followed this convenient arrangement. In Cryptic Resemblance an animal resembles some object of no interest to its enemy (or prey), and in so doing is concealed; in Mimicry an animal resembles some other animal which is specially disliked by its enemy, or some object which is specially attractive to its prey, and in so doing becomes conspicuous. Some naturalists have considered Mimicry to include all superficial likenesses between animals, but such a classification would group together resemblances which have widely different uses. (1) The resemblance of a mollusc to the coral on which it lives, or an external parasite to the hair or skin of its host, would be Procryptic; (2) that between moths which resemble lichen, Syncryptic; (3) between distasteful insects, Synaposematic; (4) between the Insectivor mole and the Rodent mole-rat, Syntechnic; (5) the essential element in Mimicry is that it is a false warning (Pseud-aposematic) or false recognition (Pseudepisematic) character. Some have considered that Mimicry indicates resemblance to a moving object; but apart from the non-mimetic likenesses between animals classified above, there are ordinary Cryptic Resemblances to drifting leaves, swaying bits of twig, &c., while truly Mimetic Resemblances are often specially adapted for the attitude of rest. use the term Mimicry to include Synaposematic as well as Pseudo-sematic Resemblances, calling the former "Müllerian," the latter "Batesian," Mimicry. The objection to this grouping is that it takes little account of the deceptive element which is essential in Mimicry. In Synaposematic colouring the warning is genuine, in Pseudaposematic it is a sham. The term Mimicry has led to much misunderstanding from the fact that in ordinary speech it implies deliberate imitation. The production of Mimicry in an individual animal has no more to do with consciousness or "taking thought" than any of the other processes of growth. Protective Mimicry is here defined as an advantageous and superficial resemblance of one animal to another, which latter is specially defended so as to be disliked or feared by the majority of enemies of the groups to which both belong-a resemblance which appeals to the sense of sight, sometimes to that of hearing, and rarely to smell, but does not extend to deep-seated characters except when the superficial likeness is affected by them. Mutatis mutandis this definition will apply to Aggressive (Pseudepisematic) Resemblance. The conditions under which Mimicry occurs have been stated by Wallace :— “(1) that the imitative species occur in the same area and occupy the same station as the imitated; (2) that the imitators are always the more defenceless; (3) that the imitators are always less numerous in individuals; (4) that the imitators differ from the bulk of their allies; (5) that the imitation, however minute, is external and visible only, never extending to internal characters or to such as do not affect the external appearance." It is obvious that conditions 2 and 3 do not hold in the case of Müllerian Mimicry. Mimicry has been explained, independently of Natural Selection, by the supposition that it is the common expression of the direct action of common causes, such as climate, food, &c.; also by the supposition of independent lines of evolution leading to the same result without any selective action in

consequence of advantage in the struggle; also by the operation of Sexual Selection.

It is proposed, in conclusion, to give an account of the broad aspects of Mimicry, and attempt a brief discussion of the theories of origin of each class of facts (see Poulton, Linn. Soc. Journ. Zool., 1898, p. 558). It will be found that in many cases the argument here made use of applies equally to the origin of Cryptic and Sematic Colours. The relationship between these classes has been explained: Mimicry is, as Wallace has stated (Darwinism, London, 1889), merely "an exceptional form of protective resemblance. Now, protective (cryptic) resemblance cannot be explained on any of the lines suggested above, except natural selection; even sexual selection fails, because cryptic resemblance is especially common in the immature stages of insect life. But it would be unreasonable to explain Mimetic Resemblance by one set of principles and Cryptic by another and totally different set. Again, it may be plausible to explain the mimicry of one butterfly for another on one of the suggested lines, but the resemblance of a fly or moth to a wasp is by no means so easy, and here selection would be generally conceded; yet the appeal to antagonistic principles to explain such closely related cases would only be justified by much direct evidence. Furthermore, the mimetic resemblances between butterflies are not haphazard, but the models almost invariably belong only to certain sub-families, the Danaina and Acraeina in all the warmer parts of the world, and, in tropical America, the Ithomiine and Heliconino as well. These groups have the characteristics of Aposematic species, and no theory but natural selection explains their invariable occurrence as models wherever they exist. It is impossible to suggest, except by natural selection, any explanation of the fact that mimetic resemblances are confined to changes which produce or strengthen a superficial likeness. Very deep-seated changes are generally involved, inasmuch as the appropriate instincts as to attitude, &c., are as important as colour and marking. The same conclusion is reached when we analyse the nature of mimetic resemblance and realize how complex it really is, being made up of colours, both pigmentary and structural, pattern, form, attitude, and movement. A plausible interpretation of colour may be wildly improbable when applied to some other element, and there is no explanation except natural selection which can explain all these elements. The appeal to the direct action of local conditions in common often breaks down upon the slightest investigation, the difference in habits between mimic and model in the same locality causing the most complete divergence in their conditions of life. Thus many insects produced from burrowing larvæ mimic those whose larvæ live in the open. Mimetic resemblance is far commoner in the female than in the male, a fact readily explicable by selection, as suggested by Wallace, for the female is compelled to fly more slowly and to expose itself while laying eggs, and hence a resemblance to the slow-flying freely exposed models is especially advantageous. The facts that mimetic species occur in the same locality, fly at the same time of the year as their models, and are day-flying species even though they may belong to nocturnal groups, are also more or less difficult to explain except on the theory of natural selection, and so also is the fact that mimetic resemblance is produced in the most varied manner. A spider resembles its model, an ant, by a modification of its body-form into a superficial resemblance, and by holding one pair of legs to represent antennæ; certain bugs (Hemiptera) and beetles have also gained a shape unusual in their respective groups, a shape which superficially resembles an ant; a Locustid (Myrmecophana) has the shape of an ant painted, as it were, on its body, all other parts resembling the back