174 



NATURE 



[December 24, 



parts, whilst the current edition is in four parts. The 

 added part is somewhat of a jumble, inasmuch as it is 

 supplementary of each of the first three parts. The 

 scheme of the book is not apparent from the list of 

 contents, and this omission results in confusion. Whilst, 

 however, the arrangement of the book is bad, the matter 

 is good. In skilful hands, indeed, the material which is 

 here accumulated might have been very attractively 

 presented. At p. 132, a dozen pages are commenced 

 on the pests of the farm, whilst another dozen pages 

 devoted to the same subject begin on p. 180. At p. 71, 

 the reader enters upon 30 pages about manures, and at 

 p. 167 he gets a further dozen pages also upon manures. 

 And so on. 



With reference to the fixation of nitrogen by legu- 

 minous plants, mention is made of the presence on the 

 roots of these plants of " little bag-like enlargements, 

 ox tubercles as they are called." It is unfortunate that 

 this effort should be made to associate the pathological 

 term '-'tubercle" with these structures. The word 

 "nodule " is much preferable, and is not less explanatory. 



Despite the fact that the book has been written to 

 enable candidates to " pass an examination," it is as 

 useful and trustworthy a little treatise of the kind as 

 we have seen. 



Eleitientary Trigonometry. By J. M. Dyer and Rev. 



R. H. Whitcombe. (London : George Bell, 1891.) 

 The title of this book is on all fours with the contents. 

 The work is well adapted for school use. The explana- 

 tions of book-work are clearly expressed, and the text 

 is amply illustrated by a store of exercises. Sufficient 

 ground is covered to meet the wants of average .Army 

 pupils. 



We have detected errata in the text on pp. 21, 30, 

 36,59,61,62,65, 67,74, 80, loi, 136, 153. The major 

 part of the proof-sheets has been carefully gone over, 

 but occasionally, as we have indicated, the authors have 

 nodded. The printing in places, in our copy, is defec- 

 tive. But these faults only slightly mar a work which 

 treats a hackneyed subject with all the freshness one can 

 look for in an elementary text -book. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of iiATUB.^. 

 No notice is taken of anonymous communications. ] 

 Opportunity for a Naturalist. 



Since the completion of " Argentine Ornithology," in which 

 was given an account of the 434 species of birds then known to 

 occur in the Argentine Republic, Mr. Arthur Holland, of the 

 Estancia Espartilla, and Mr. J. Graham Kerr, of the Pilcomayo 

 Expedition, have made excellent contributions to the .same sub- 

 ject, and have added some 30 species to the Argentine avifauna. 

 But much more remains to be done, and, in continuation of the 

 work, I am now anxious to get a good series of birds from 

 Uruguay, the fauna of which, so far as we know it, does not 

 appear to differ materially from that of its neighbouring Re- 

 public. For this purpose I have made arrangements with a 

 friend to take in a naturalist at his Estancia, near Minas, about 

 sixty miles from Monte Video, and am looking for a qualified 

 collector to occupy the post. His necessary expenses will be 

 met, but his further remuneration must de end, more or less, on 

 the results obtained. May I ask the aid of Nature to make 

 known this eligible opportunity for a young naturalist who can 

 make good birds'-skins, arid is anxious to pass a few months in 

 a foreign clime ? P. L. Sclater. 



3 Hanover Square, London, W. 



Warning Colours. 

 Mr. Beddard, in his letter published in Nature of Novem- 

 ber 26 (p. 78), calls attention to Dr. Eisig's suggestion that 



NO. I 1 56, VOL. 45] 



those bright colours of animals which have hitherto been re- 

 garded as of warning significance are merely the substances 

 which confer the unpleasant taste, and that therefore the older 

 interpretation is unnecessary and in fact erroneous. The writer 

 furthermore implies that Dr. Eisig's views are not alluded to by 

 those who have written upon animal colours, because they have 

 escaped their attention. There is, however, another possible 

 explanation of such neglect, and one which in my own case is 

 certainly the correct one — viz. that the views in qut-stion appear 

 to be so inherently improbable that a large body of confirmatory 

 evidence is required before they demand attention. I do not by 

 this mean to suggest that the unpalatable attribute may not 

 possess a bright colour : this is certainly often the case, espe- 

 cially with the secretions expelled by many insects when they- 

 are irritated. But it is highly improbable that these facts afford 

 any refutation of the theory of " warning colours" — that is, of 

 the view which regards the bright and conspicuous colouring as 

 an indication (in mimetic forms a false indication) of some un- 

 pleasant attribute, whether associated or uuassnciated with the 

 colour itself. And as regards the bright colours of Lepidopterous 

 imagines, such association is, to say the least of it, entirely unproved. 

 It by no means follows that the yellow colouring of the brim- 

 stone and other butterflies is disagreeable in flavour because it 

 " is due to a substance formed as a urinary pigment." And the 

 relation of many animal colours to these pigments by no 

 means necessarily implies unpalatability. Again, it would be 

 impossible to regard merely as a coincidence the fact that the 

 substances in question almost invariably produce a conspicuous 

 appearance, and, furthermore, produce it in a variety of ways. 

 Such an appearance is, as is well known, not merely due to the 

 individual colours, but to their mutual arrangement and relation- 

 ship. It is due, moreover, to a variety of physical principles, 

 for the production of white is very different from the production 

 of the colours which are so often contrasted with it. Con- 

 spicuous effects are furthermore often gained without the use of 

 pigment, as in the brilliantly metallic pupae of Etiplcea core and 

 oi Mechqnitis lysimnia. Hence the contention that the bright 

 colour of distasteful insects is a mere incident of chemical com- 

 position which has been selected on other accounts is so 

 inherently improbable that it would require a large body of 

 evidence to support it. 



But perhaps the strongest argument against the view is that 

 it creates such an artificial distinction between inedibility due to 

 mere unpalatability, and that due to other unpleasant attributes. 

 Mr. Beddard would probably admit that the conspicuous 

 colouring of the skunk, the coral snake, and the wasp pos- 

 sesses a true warning significance ; and yet he would interpret 

 the black and yellow colouring of the larva of the cinnabar 

 moth or the pupa of the magpie moth (both known to be un- 

 patable) in an entirely different way, and would deny that it 

 possesses a warning meaning. 



In addi;ion to these considerations, the undoubted existence 

 of an unpalatable quality not residing in the superficial pigments 

 is quite clear in many brightly coloured insects. The irritating 

 hairs and odoriferous secretions of many Lepidopterous and 

 Hymenopterous larvae, and the evil-smelling yellow fluids which 

 exude from CoccinellidcE and from many conspicuous butterflies 

 are examples. 



The recent investigations of the distinguished Russian 

 naturalist Portchinsky (II. "Coloration marquante et taches 

 ocellees, leur origine et leur developpement," St. Petersburg, 

 1890) have, among other things, shown us the distinct manner 

 in which the colours which attend unpalatability are displayed 

 by the insect when it is disturbed. He thus explains some of 

 the cases of "shamming death" which are so often alluded to 

 in works on insects (the other cases being explained by the 

 necessity for concealment). Two examples which he adduces 

 are so interesting, and have so important a heading on this dis- 

 cussion, that I cannot resist the temptation of reproducing them 

 here, especially as Portchinsky's paper, being written in Russian, 

 is almost unknown in this country. I have, however, been 

 most kindly helped by my friend Mr. MorfiU, and now possess a 

 complete translation, which I hope soon to publish. The 

 female of Spilosoma mendica possesses black and yellow legs, 

 and, when disturbed, it folds its limbs and drops to the ground, 

 generally falling on its back, so that the contracted colours are 

 displayed (see Fig. i). In the closely allied Spilosoma tirtica 

 the dorsal surface of the abdomen is blacl< and yellow, and this 

 insect, when irritated, raises its wings and curves the abdomen 

 downwards so that the colour is conspicuous. Furthermore, 



