ANIMAL CHLOROPHYLL 375 



has been carried on by the English investigator Poulton, who 

 found that the pigment of a large nmnber of insects (in all 

 stages of development) is a modified chlorophyll derived from 

 the plant on which the animal feeds. The chlorophyllous 

 substances are eaten, absorbed into the blood-system, and 

 deposited in the regions of the body exhibiting pigmentatior. 

 The most valuable results in Poulton's work came from 

 a spectroscopic examination of insect blood. His (1884) 

 work on the pigment of Sphinx ligustri is interesting. 

 The blood from the pupae of this form was examined and its 

 spectrum recorded ; then an extract was made of the calceolaria 

 leaves upon which the larva feeds. When the spectrum of the 

 extract was superimposed upon that of the blood, the bands 

 were found to correspond in a very striking way. In Poulton's 

 own words (p. 290) : 



' Considering the chemical change which nuist have taken 

 place in the chlorophyll during digestion, rendering possible 

 the passage of the walls of the digestive tract, and considering 

 its chemical union with the proteid constituent of the blood, 

 the resemblances of the spectra are very striking ; in fact, the 

 two spectra are far nearer each other than the ordinary spectrum 

 of chlorophyll in alcoholic solution is to the unaltered chloro- 

 phyll of leaves '. 



It was held by Poulton that the power of utilizing chloro- 

 phyll in building up pigments is an adaptation on the part of 

 the insect which enables it to assume the colour of the leaves 

 on which it feeds. As evidence for this he brought forward 

 the fact that if larvae of Trypoena pronuba are fed 

 respectively on green, brown, and white cabbage leaves, green, 

 brown, and white larvae result according to the colour of the 

 leaf on which they were fed. This result has since been corro- 

 borated by Levart et Conte (1902), who worked on Attacus 

 Orizaba and Bombyx mori. 



Peterson (1913) has found that the chlorophyll which passes 

 into the intestine of certain red caterpillars is modified into 



1 Poulton has written a large number of papers on this subject. The 

 more important ones will be found in the bibliography under Poulton, 

 1884, 1889, 1892, and 1893. 



NO. 262 D d 



