CAROTINOIDS IN INVERTEBRATES 159 



Carabus auratus, a phenomenon also noticed by Sorby (1871c) in the 

 case of green Aphids. There can be little doubt that the yellow pig- 

 ments found in these insects are often, if not always, true carotinoids. 

 Thus, Zopf (18921)) describes the properties of the orange pigment in 

 the wing coverings of the willow-leaf beetle Clythra quadripunctata, 

 ;is showing all the usual lipochromc reactions (including his lypocyan 

 reaction described in Chapter III), and the absorption bands in 

 petroleum ether lying at 496-480^1 and 460-448[i[i. Zopf called the 

 pigment a di-carotin or "eucarotin." The absorption bands indicate 

 carotin itself. The same pigment was found in the yolk of this insect's 

 eggs. Schulze (1913, 1914), although he has examined the pigments 

 less critically from a chemical point of view, has adopted the idea that 

 the yellow and orange pigments in the wing coverings of many beetles 

 are true carotinoids. He has examined especially the species Mela- 

 soma XX-punctatum, Melasoma populi, Chrysomela polita and Chry- 

 somela t'cirians. He states (1914) that the pigments appear to ap- 

 proach the xanthophylls, rather than carotin, in their properties, but 

 does not present the chemical evidence for this statement. 



The red pigments of the beetles appear to belong to the carotinoid- 

 like class of pigments which have been mentioned repeatedly in the 

 foregoing pages under the names carotinin, rhodophane, zoonerythrine, 

 etc., which are characterized especially by showing only one absorp- 

 tion band at the F line. Zopf (1892b) described the properties of 

 this pigment in the poplar leaf beetles Lina populi and Lina tremulce, 

 as well as the beetles Coccinella septempunctata and C. quinque- 

 punctata. Zopf found the pigment in the wing coverings, on the abdo- 

 men, on the lateral edges and end of the back, and also in the eggs 

 of the poplar leaf beetles. He also noticed that the latter insects 

 secreted the pigment from the mouth when excited by handling or 

 stimulated by chloroform. The Coccinellce also secreted the pigment, 

 but the secreting cells were found to be in the joints, not in the mouth. 

 Zopf described the solubility of the pigment in the fat solvents and 

 in oils, the lipochrome color reactions, including the lipocyan reac- 

 tion, and the single spectroscopic absorption band shown by the ether 

 solution at 515-480uu. At the time of his investigation of the pig- 

 ment Zopf called it a mono-carotin, but later (1893a) referred to it 

 as Lina-carotin. Griffiths (1897) attempted to ascertain the com- 

 position of the pigment, which he called coleopterin, using the species 

 Pyrochra coccinea, Lina populi and Coccinella septempunctata as 

 the source of his material. The extracts secured, using boiling alcohol 



