CHAPTER VIII 



INSECTS, ARACHNIDS AND REPTILES 



INSECTS 



Although a considerable amount of work has been carried out on 

 the carotenoid biochemistry of insects, a great deal still remains to be 

 done, especially on problems of metabolism and function. 



COLEOPTERA 



Zopf ^ in 1893 discovered a carotenoid in the elytras, body wall and 

 eggs of Lina populi and L. tremulae and named it " linacarotene " ; 

 it also occurs in the yellow juice which excited animals excrete. Zopf also 

 found that it was present in the same tissues of the lady birds, Coccinella 

 septempunctata and C. quinquepunctata. In 1933 WalP reported the 

 presence of carotene in C. novempunctata, but it was Lederer ^ who in 

 1934 carried out the first intensive chemical investigation on the 

 Coleoptera ; he used Coccinella septempunctata and found that the 

 elytral linacarotene was, in fact, a mixture of a- and ^-carotenes and 

 lycopene. No free xanthophylls were present but very small amounts 

 of xanthophyll esters were found in the rest of the body. 



According to the early investigations of Palmer and Knight* the 

 potato (Colorado) beetle Leptinotarsa decemlineata contains carotene 

 but no xanthophylls ; much more recently Manunta ^ has claimed that 

 the main carotenoid of this beetle is similar to that extracted from the fat 

 of the flamigo {Phoenicopterus roseus (see p. 260) and named phoenico- 

 xanthin (but see p. 260). It is obvious that this beetle deserves further 

 investigation. Palmer and Knight found an extraordinarily high 

 concentration of carotene 13,600 [xg. per 100 ml. in the haemolymph of 

 L. decemlineata compared with that found in mammalian {e.g.^ human) 

 plasma (see p. 236), similar high values are found in locust haemolymph 

 (^e^p. 219). 



The flour beetle, Tenebrio molitor^ can exist on diets devoid of 

 carotenoids and does not manufacture any of these pigments de novo. ••' 



Lepidoptera 



In 1885 Poulton^ stated that the haemolymph larvae and chrysalides 

 of lepidoptera, contained carotenoids which originated in the insects' 

 food ; the pigment in the haemolymph being attached to the protein. 



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