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Rh governor in 1918, and reelected him in 1920 with an increased majority and a Legislature almost completely Republican.

During the World War, approximately 45,000 men from Colorado served in the army, navy and marine corps, of whom about 22,000 had been drafted. There were in the state 698,169 subscriptions to the Liberty and Victory loans, amounting to $144,813,550, which was 24% more than the quota.

Bibliography. Wilbur Fiske Stow, History of Colorado (three vols., 1918); Jerome C. Smiley, Semicentennial History of Colorado (1913); Irving Howbert, Indians of the Pike's Peak Region (1914); Prof. James F. Willard, Union Colony of Greeley (State Univ. Hist. Col- lections, 1918); Enos A. Mills, Spell of the Rockies (1911), Rocky Mountain Wonderland (1915), In Beaver World (1913)- Your Na- tional Parks (1917); E. Parsons, Guide Book to Colorado (1911); A. C. Carson, Colorado, the Top of the World (1912) ; Mae Lacy Baggs, Colorado, the Queen Jewel of the Rockies (1918); Alice Palk Hill, Colorado Pioneers in Picture and Story (1915). (C. A. D.)

COLOURS OF ANIMALS (see 6.731). Since 1910 the knowledge of animal coloration has been added to in many directions. Broadly speaking, however, the new facts confirm the views previously held, which are only modified in points of detail.

Cryptic Colouring. As regards cryptic coloration, A. H. Thayer and his followers have shown that many arrangements of colour and pattern which had been previously considered to be revealing, are in truth concealing. A few biologists go so far as to express the view that all coloration is concealing and explain all cases of the mimicry of one animal by another, as due to a common cryptic (syncryptic) coloration, both animals having independently developed the same concealing coloration. Apart from mimicry, there are great difficulties in maintaining this thesis. The habits of many brilliantly coloured animals clearly prove that they do not seek to hide themselves but rather to show off their bright colours.

Mention may be made of the method of concealment by dis- ruptive coloration first described by Thayer. This is for the concealment of animals likely to be seen against two or more backgrounds. An animal, for instance, coloured green and brown in large areas, when viewed against a green background will be visible in respect of its brown areas, and as these brown areas will not have the shape of the animal but will be like one of the many oddments of nature (stones, leaves, etc.) so the animal will be mistaken for one of these. It will be similarly concealed against a brown background: in this case, only the green areas will be noticed. In these cases concealment is effected by dis- rupting the characteristic outline of the animal. The white areas which many animals present, are considered to be for disruption against the background of the sky, as, for instance, when a partially white bird in a tree is viewed against the low horizon. Many experimental findings and field observations form the basis of these conclusions.

Another use of pattern is to give a blurred or indistinct appear- ance to an outline. It is common to find, along the margin of the wings of butterflies and moths, a very small black and white, or contrasted, pattern which is visible at short distance; at longer range the pattern blends and then the margin has an indistinct appearance, causing the insect to fade into its back- ground. The finely spotted, barred and striped patterns of many mammals and birds are similarly effective in concealing the outlines at distance the spots cannot be seen.

The solidity of an animal is concealed by what is now called counter-shading, namely, by the darkening of surfaces exposed to the light, and the whitening of those in shadow. Large dark spots or broad dark stripes on the back, gradually changing to small spots and narrow stripes on the under sides, has the same concealing effect and the added advantage of a blurred outline when the animal is viewed at a distance. The very remarkable striped pattern of the zebra has been considered to be of this nature. In some animals not only is their solidity thus concealed, but a false solidity or modelling is superimposed. A flat surface is often made to appear rough or uneven: this is effected by an arrangement of light or dark tones used in a manner precisely similar to that by means of which the artist produces the de- lusion of a solid object on a flat canvas.

The use of colour in animal coloration can at present only be very imperfectly understood because little is known of the colour vision of animals. There is some evidence that animals have a colour perception less sensitive than man: if such prove to be the case, then a ready explanation for several dimorphisms is available. For instance, among insects it is common to find that whilst some individuals of a species are green, others are brown; but towards a colour perception slightly less sensitive than man's, these colours will be indistinguishable, and thus against either green or brown backgrounds neither the brown nor green individual would have the advantage. A common defect in man's colour sense is an inability to distinguish red from green; it is possible that such a colour as the red of the robin's breast against green foliage may serve to conceal the bird from its enemies.

When bright colours are used for revealment, as shown by the animal's habits, and by the particular pattern and position which the colour occupies, then advantage appears to be taken of the fact that red is a very conspicuous colour at high illuminations and blue at low illuminations. The brilliant inhabitants of the forest present a preponderance of blue, whereas red is more often found among those living in the open. This also apph'es to flowers, the bluebell typifying the colour for woods and the poppy for the open.

Experiments have shown that it is possible to determine, in many cases, whether a given pattern is for concealment or re- vealment: for instance, it has already been mentioned that concealment may be effected by a pattern which breaks out along the animal's margin and thus tends to conceal its char- acteristic shape. Conversely, patterns which follow an animal's margin and tend to accentuate its characteristic shape and separate it from its surroundings, make for revealment. A pattern of this kind, commonly seen in butterflies, is a broad black band following the outer margins of both wings and often enclosing a brilliant yellow or blue central area. Experimental evidence of this kind, as well as that derived from a study of an animal's habits, is strongly against the view that all coloration is for concealment.

The concealment of cast shadow is commonly brought about by the crouching or squatting of either hunted or hunter. Among butterflies Marshall has pointed out two methods of avoiding cast shadow: Certain species when resting on the ground with closed wings will tilt over the wings, generally away from, some- times towards the sun, thus reducing and hiding the shadow cast upon the ground. Other species will settle on the ground with wings spread and orient themselves so that either their head or more often their tail is pointed at the sun. Should a bird or other enemy come near they at once close the wings over the back and then only a line shadow of the wings is cast on the ground.

Sematic Colouring. Passing on to the consideration of sematic or signaling coloration, certain advances have been made. Feeding experiments have shown that the preyed-upon can be arranged in a series, for any given preyer, from the most to the least palatable. The former will be eaten when the preyer's hunger is almost satisfied; the latter, only when the preyer is starved. The colours of this series are then found to be arranged from cryptic coloration corresponding to the very palatable, to a revealing (warning) coloration for the very unpalatable. Further, it has been observed that in many cases, whilst con- cealment by a cryptic coloration is the usual form of protection, nevertheless, a revealing coloration is exhibited to the preyer, when concealment has failed. This revealing coloration, such as the hind wing of a moth, is as a rule hidden by a cryptically coloured fore wing, and is only revealed at the last moment to advertise a relative unpalatability. There is also evidence ob- tained from watching feeding birds, that revealing coloration is used for deception in the manner of a conjuring trick. Thus, the Leaf butterfly (Kallina) when flying appears blue and yellow, but directly it settles with closed wings it becomes like a dead leaf: the pursuing bird will continue to look for the blue and yellow insect among the dead leaves in which the insect has taken