XL 



in white boxes can easily be accounted for. That bodily functions — and this 

 applies especially to secretions — are not exercised, or only partly so, under 

 abnormal conditions is indeed no uncommon phenomenon ; thus the secretion 

 of dark pigments might well be impeded by the disturbance here referred to, 

 either absolutely or to such an extent that the cocoon threads, originally white, 

 might become coloured in which latter case insufficient moisture of this secretion 

 might be the determining factor and Federley's experiment would, therefore, 

 be to the point here. This would again be a case of disturbance in the 

 natural course of development caused by white light, which would very well 

 accord with the forementioned interpretation of the action of yellow and orange 

 light on PiERis pupae. This appears to me to receive equal confirmation from 

 Poulton's experiments with the pupa of Vanessa Urticae L. As we have seen 

 by exposing these pupae to bright white light he obtained a few pink ones but 

 by far the greater number were very light in colour with an extraordinary 

 development of the golden spots, even causing a complete gilt appearance of 

 some of the pupae ; illumination with gilt surroundings, thus irradiating a bright 

 yellow light, further increased the number of strongly gilt pupae. In this 

 butterfly a very intense white or yellow light, however, appears to be required 

 for this ; simple white surroundings, such as white paper which influences the 

 cocoons of Heterocera, appears to be insufficient ; pupae of Pieris species and 

 of Papilio Machaon L. placed against a white wall became darker, not light ; 

 pupae of Pap. Memnon L. attached to white gauze assumed a dirty white. 

 Similar surroundings, however, may, as we have seen, produce different effects 

 in different species. 



PouLTON was particularly pleased with his quasi-alchemic discovery of the 

 almost completely gilded pupae and, in the same manner in which phenomena 

 of mimicry are so hotly chased, the appearance in nature of golden spots, such 

 as occur in the pupa of Vanessa Urticae L., for instance, is attributed with 

 great ingenuity to a similar illumination or even where it may be observed on 

 a much larger scale as in South America — or for instance in the Malayan 

 EuPLOEAS — it is interpreted as a vestige of earlier conditions of similar illu- 

 mination ! But upon serious reflection there is no ground whatever for attributing 

 these strong and wide-spread metallic lustres, such as occur for instance in the 

 pupae of EuPLOEA and Atella, to such influence ; moreover the same occurs 

 in other life-stages of Lepidoptera. In the case of larvae, indeed, few instances 

 are known, although I recollect referring on page 56 of the Monograph of the 

 Java Pieridae to the steel-blue lustre of some cateq)illars of Callidryas Pomona F. ; 

 in imagines, however, many examples are met with ; the metallic spots on the 

 lower surface in some species of Argvnnis and those on the upper surface of 



