PIGMENTARY COLOURS 187 



plant chlorophyll. His argument does not appear very conclusive, 

 because insect chlorophyll has never been claimed to be absolutely 

 identical with plant chlorophyll. Furthermore, he apparently 

 did not investigate the pigments of Lepidopterous larvae. Gerould 

 (1927) criticises Przibram's conclusions and points out that the 

 reactions described are such as one would expect in cases where 

 the pigments are associated with proteins, as in the blood of 

 Lepidopterous larvae. 



Faure (1932) has shown that in the solitary phase of the African 

 Migratory Locust (Locusta migratoria subsp. migratorioides R. 

 and F.) green individuals are of frequent occurrence. This same 

 feature has also been observed by Hertz and Imms (1937) : the 

 green coloration only develops in the presence of a relatively 

 high humidity and is independent of the coloration of the 

 immediate environment and of food. Faure finds that the green 

 pigment involved betrays no close affinity with chlorophyll. It 

 shows, for example, a single absorption band with its centre at 

 6,700 A. and there is no trace of the red fluorescence characteristic 

 of chlorophyll solutions. In the stick insect Carausius (Dixippus) 

 and many caterpillars the green pigment is also apparently 

 synthesised by the insect itself and is developed independently 

 of the nature of the food (Giersberg, 1928 ; Meyer, 1930). Accord- 

 ing to Meyer it is an oxidation product of protein metabolism. It 

 is evident, therefore, that due precaution must be exercised before 

 concluding that the green colour of many insects is a chlorophyll 

 derivative. 



Another group of plant pigments, namely, the anthocyanins, has 

 recently been shown to be present in insects. According to 

 Hollande (1923) certain insects absorb pigments of this nature 

 from their food which become concentrated in the albumen granules 

 of the fat-body. Thus, the larva of the beetle Clonus olens, which 

 feeds upon the purple staminal hairs of Verbascum nigrum, con- 

 tains an anthocyanin derived from that plant ; the pigments 

 remain purple or become coloured either blue or red according to 

 the prevailing degree of alkalinity or acidity present. A blue 

 pigment of a similar nature was also found by him in larvae of the 

 saw-fly Athalia spinarum. In the bright vermilion-coloured aphid 



