\ 



August 13, 1903] 



NA TURE 



357 



dispute that the arrangement and nature of the colours in 

 the kiang must render it practically invisible when stand- 

 ing in the desert at a distance. But this is not all. Why 

 are the legs, or at least the greater part of them, and the 

 backs of the thighs up to the root of the tail also white? 

 This is doubtless the reason. When the kiang rests on the 

 ground in the attitude characteristic of ungulates, with the 

 hind-quarters depressed, the fore-legs folded and the hind- 

 legs tucked in close to the body, the white on the back of 

 the thighs is brought into line with that of the belly, and 

 a continuous expanse of white, obliterating the shadow, 

 extends all along the underside from the knee to the root 

 of the tail. So, too, with the quagga. This, then, is the 

 meaning of the change in pattern presented by the African 

 species as it passed southwards into Cape Colony. In 

 correlation with the adoption of a life in the open, a new 

 method of concealment by means of shadow counteraction 

 was required, and was gradually perfected by the toning 

 down of the stripes on the upper side and the suppression 

 of those on the hind-quarters, belly and legs. 



The same alignment of the white on the rump and belly 

 may be seen in many antelopes, like gazelles, and the co- 

 operation of the legs in increasing the underlying area of 

 white is especially well shown in the bonte-bok. 



Now the rump-patches, be it noted, only subserve the 

 purpose here suggested when the animals that possess them 

 are lying on the ground. This, however, is the time, as 



\ A suspici -lus inconstancy about their coloration inclines m.% to the 

 opinion that these ponies are the descenJants of "runaways." 



ance to the body and destroying the evenness of its surface 

 owing to the difference in light-reflecting power between 

 hairs of these hues to which domestic horses bear witness. 

 Moreover, the extension of the stripes to the very edge of 

 the body and legs breaks up the continuity of the outline, 

 and this, I believe, is the reason for the alteration in their 

 direction on the hind-quarters and limbs, so that, except on 

 the forehead, the whole animal is barred transversely with 

 reference to its spinal and appendicular axes. 



We have also the positive assurance of observers that the 

 asses of the deserts of North-East Africa are perfectly 

 adapted to their surroundings in colour, and no one can 

 doubt that the assimilation is equally perfect in the case 

 of the kiang and Prjevalsky's ponies ' of Central Asia. In 

 the matter of colouring the kiang forcibly recalls the typical ! 

 quagga, despite a decided difference in the deepness of the ! 

 brown pervading the upper parts in the two species. Not- j 

 withstanding this difference, there can, I think, be no ; 

 question that the explanation to be given of the significance I 

 of the colours of the kiang applies with equal truth to the | 

 quagga. This explanation is the hypothesis of the counter- 

 action of light and shade put forward by the American | 

 artist, Thayer. i 



It would be hard to find a better and simpler instance of j 

 this style of coloration than the kiang. The upper parts on i 

 which the light falls are of a rich ruddy hue, darker than 

 ordinary sand, while the muzzle, the lower side of the head, 

 the throat and the belly are creamy white. Surely no one 

 with a knowledge of the truth enunc i riiavfr will 



they drowsily rest or chew the cud, when concealment is 

 of the greatest importance to ungulates, which are, for 

 the most part, clumsy' risers, and slow at getting under way. 

 When standing and on the alert, their need for conceal- 

 ment, though seldoin absent, is certainly less, and when 

 they are on the run all idea of it is thrown to the winds. 

 It is then that the rump-patches act, as Mr. Wallace 

 suggested, as danger signals and " foUow-the-leader " 

 marks, showing the young and inexperienced which way 

 to go, and helping the members of a herd to foregather in 

 the dark when dispersed by the panic of a night attack. 



The pattern of a zebra, in its entirety, is also believed by 

 Mr. Wallace to have a double significance analogous to the 

 above. It is known to be procryptic ; but he holds that it 

 acts as a badge of recognition, enabling the zebras to 

 distinguish their own kind amongst the herds of other beasts 

 that may be feeding in the same place. It may be so ; for 

 although seemingly contradictory, the two explanations are 

 not mutually exclusive. The procryptic effect of the pattern 

 is largely a matter of distance and light. At close quarters 

 in broad daylight a zebra is conspicuous unless under cover, 

 and the colouring is strikingly unlike that of other animals. 

 On the other hand, it must be remembered, as I have else- 

 where pointed out (Nature, October ii, 1900), that the 

 species, like wildebeests, zebras, spring-buck, or even 

 ostriches, which formerly at all events fed together upon 

 the veldt,' are so dissimilar in size and shape that the need 

 for a distinctive type of coloration to prevent the postulated 

 likelihood of specific confusion can hardly have been a 

 sufficiently important factor in survival to have guided the 

 evolution of the colour for the purpose supposed. And since 

 we have evidence of the best kind that the pattern of zebras 

 and quaggas is procryptic, it seems unnecessary to look 

 further for its explanation. R. I. PococK. 



AGRICULTURAL NOTES. 



TN the recently published number of the Journal of the 

 South-eastern Agricultural College, Wye, Mr. Theobald 

 gives an account of some injurious flea-beetles (Halticae) 

 which he has recently studied. He finds that the damage 

 ascribed to the turnip " fly " {Phyllotreta nemorum) is very 

 often due to related genera. A troublesome attack of the 

 " fly " at the College farm drew attention to a new culprit, 

 Haltica olcracea, and in observations made in Yorkshire, 

 Carnbridge, Huntingdon, Surrey, Kent and Devon, this 

 species was found to be much more destructive than P. 

 nemorum. The characteristics of five injurious genera are 

 described, and observers are asked to collect and report 

 upon these very destructive insects. Mr. Theobald's ex- 

 perience leads him to remark that " The present economic 

 entomologist relies on the past economic entomologist, and 

 so errors go on until they really seem facts. . . . John 

 Curtis wrote the most excellent article on the turnip flea 

 that can be imagined, and we have all copied it." Mr. 

 Theobald's request for " serious reporting and collecting " 

 should appeal to a wider circle than is reached by the College 

 Journal. The entomologist is not the only worker who 

 relies on the achievements of the past, nor is economic 

 entomology the only branch of applied science that may 

 learn something from this study of the Halticae. 



In the same number Principal Hall, until recently head 

 of the College, summarises the results of manurial experi- 

 ments on the hop, which have been carried on at various 

 centres for from three to eight years. He concludes that 

 the hop plant is " an all-round feeder," in this respect 

 differing from such crops as swedes, which depend mainly 

 on phosphates, and from potatoes, which must be liberally 

 dressed with potassic manures. No one special manure can 



i These odd friendships are a great puzzle ; but perhaps the following 

 sugtestions may throw some light upon their occurrence and uie. It is 

 unlikely in the extreme that all the species concerned have their sense 

 organs developed to an equal pitch of excellence. In one the sense of 

 smell, in another the sense of sight, in a third the sense of hearing will be 

 pre-eminently keen. Hence the sensory imperfections of one species will 

 be made good by the proficiencies of the others ; and each will be benefited 

 by the association. Ostriches, for instance, in virtue of their stature and 

 long sight, will see an enemy in open country at a much greater distance 

 than will zebras or gnus, and will give the alarm by starting to run. Zebras, 

 on the other band, will scent a lion creeping up under cover long before the 

 ostriches will see him ; and by making off will warn these birds and other 

 duller scented members of the incongruous assemblage that danger is afoot. 



NO. 1763, VOL. 68] 



