Mabch 24, 1899.] 



SCIENCE. 



449 



with an account of animal and plant coloration 

 which will cover the ground as completely as 

 the knowledge of the day permits. In the 

 meanwhile, we may be grateful to her for a 

 work which will at any rate serve as an excel- 

 lent introduction to the subject, and as more or 

 less of a revelation to those whose studies have 

 been confined to a limited field. 



Attention is drawn to the interesting analogy 

 between natural color-variations of organisms 

 and the changes which can be induced in their 

 pigments bj' suitable reagents. This is a mat- 

 ter which, though well known, has not received 

 the attention it deserves, partly because those 

 aware of the chemical reactions have not usu- 

 ally been familiar with the natural variations, 

 and vice versa. It may be permissible, by way 

 of illustration, to cite two new instances of this 

 among the Coccidse which have just come to 

 the writer's notice. Icerya rileyi has a pure 

 white ovisac, which is turned bright primrose 

 yellow by chloroform, but regains its white 

 color when the chloroform evaporates. A 

 closely related form, Icerya littoralis, var. 

 mimosx, has the whole ovisac naturally of a 

 delicate primrose yellow. The second case is 

 more instructive. Mytilaspis concolor has ordi- 

 narily a white scale, but on February 5, 1899, 

 Mr. P. J. Parrott discovered a variety (M. con- 

 color var. viridissima, Ckll. and Parrott, ined.) 

 in which the scales of both sexes are of a lively 

 emerald green. This was on the campus of 

 the Agricultural College, Mesilla Park, at the 

 bases of stems of Atriplex canescens. The 

 female insect itself, removed from beneath the 

 scale, was found to be of a dark purple color, 

 with a bright yellow patch in the anal region, 

 and suffused crimson spots at intervals round 

 the margins of the hind end. The purple 

 color, when the insect was placed in caustic 

 soda, immediately became green, but was changed 

 back to purple by acetic acid. Now, it is evi- 

 dent in this case that the insect must have had 

 an acid reaction, but the pigment transferred 

 to the scale had apparently been turned green 

 by the ' alkali ' salts which are known to occur 

 in the soil at Mesilla Park. This at once re- 

 calls the chsetopterin pigments described by Dr. 

 Newbigin on pp. 89-91 of her work, and it may 

 be that we have a new member of that series. 



On pp. 161-162 it is suggested that the re- 

 semblance between certain Heliconian butter- 

 flies and their Pierid mimics may be due, at 

 least in part; to their relatively low organiza- 

 tion and simple plan of coloration. In the 

 Transactions of the Entomological Society of 

 Loudon, 1891, Mr. H. H. Druce published a 

 paper on the Lycsenid genus Sypochrysops, 

 which inhabits Australia and the Malay Archi- 

 pelago. To this paper are appended two beau- 

 tiful colored plates, aud the present writer was 

 surprised to find that he could nearly match a 

 number of very diverse species figured, as to 

 color and pattern, 'among a series of Lycsenidse 

 collected in Jamaica ! The resemblance per- 

 tained only to the upper surface of the wings, 

 the lower surfaces of the Jamaican insects being 

 quite unlike Hypochrysops. Now the Lycsenidae 

 show splendid ' optical ' colors, and are cer- 

 tainly not simply organized as regards their 

 coloration, so the suggestion made with regard 

 to the Heliconians aud Pierids would not hold. 

 Neither, of course, is there any true mimicry, 

 since the two sets of butterfiies occur on oppo- 

 site sides of the world. Cases of this sort have 

 been quoted as destructive to the theory, of the 

 utility of mimicry among insects, but to the 

 writer they seem only to remove the difiiculty 

 which was felt in accounting for the origin of 

 genuinely mimetic resemblances. 



In a work of the kind now under review 

 there must necessarily be details which could 

 be adversely criticised. The writer had begun 

 to take note of such, but it hardly seems worth 

 while to dwell upon them. Botanists will un- 

 doubtedly complain that the space devoted to 

 the colors of plants is much too short, and that 

 several of the statements therein are too general 

 or too sweeping. It will probably be thought 

 by many readers that if Dr. Newbigin had 

 made more or closer observations of living 

 animals she would have had greater respect for 

 natural selection. And, finally, some will 

 wonder how it is that one who has enjoyed the 

 beautifully pure colors of living creatures can 

 have permitted her book to be bound in such a 

 muddy and unpleasing blue. 



t. d. a. cockeeell. 



Mesilla Paek, New Mexico, 

 February 27, 1899. 



