CHRYSALIDS AND TIIKIR SURROUNDINGS. 1579 



laritics of many ohrvsalids among tlic Xymphalidao, combined with their 

 tVequent liriiiianey hy roHeeted colors, golden or nacrcons, which, in com- 

 bination, would be strikingly similar to the metallic gleam of angular 

 minerals in the rocks whicii form their natural backsrround. 



This last circumstance, to whi<'h attention has been specially called by a 

 very painstaking cxi)erimental entomologist of England, Mr. E. B. Poul- 

 ton, led him to a careful inquiry into the cause and extent of the special 

 color relations existing between the chrysalids of butterflies and their sur- 

 rounding surfaces (Phil, trans., clxxviii : 311-441, pi. 2(5). lie has been 

 able to obtain almost at will chrysalids of diff'erent colors, according to the 

 tints with wliich he has surrounded them, and so has opened anew field of ex- 

 perimental inquiry wliich may yield important, as it already has interesting 

 results. By carefully selecting the time at which his experiments were made 

 he has been able to determine that in all the species experimented upon it was 

 only necessary to confine attention to that period in the later larval life 

 of the insect, when it has ceased feeding and remains motionless, together 

 with the early portion of the next period, after spinning the silken pads 

 and shrouds for the pupal attachments until it has thrown off the larval 

 skin. It had already been pointed out by Meldola that it was impossible 

 to suppose the moist skin of the freshly formed pupa photographically 

 sensitive to the color of the surrounding surfaces, and this has been made 

 perfectly evident from the experiments of Poulton, which show that the 

 color is determined before the assumption of the pupal state, since experi- 

 ments made later than the time mentioned produced absolutely no results. 

 Neither was Poulton successful , as he seems to have expected to be, in 

 preventing the influence of surrounding objects from reaching the nervous 

 centres through the ocelli of the caterpillar. All his successful experi- 

 ments came when applied to that period of the transformation to which we 

 have referred. 



^lost of the experiments were made upon three species, Aglais urticae, 

 Mancijiium brassicae and Pieris rapae. The experiments consisted in pre- 

 paring for the creatures during their changes, artificial surroundings of 

 difl^erent colors, green, orange, black, white and gilt. Over seven hun- 

 dred chrysalids in all were experimented upon and it was found that with 

 Aglais urticae green and orange surroundings caused no effect on the pupal 

 colors, black produced as a rule dark chrysalids, while white produced 

 light colored ones, many of the last being brilliantly golden ; this sug- 

 gested the use of gilt surroundings, which were far more efficient than 

 white and produced chrysalids of a distinctly golden color, more so even 

 than often occurs in a state of nature. The influence of black was curiously 

 shown by the fact that when the caterpillars changed to chrysalids upon 

 light surfaces, those which underwent their transformations in close prox- 

 imity were darker than those that were more isolated, the color of each being 



