INSECTS, ARACHNIDS AND REPTILES 



Meyer • stated that carotenes were present in the haemolymph of 

 nine famihes of lepidoptera. In particular, only ^-carotene existed in 

 the haeolymph and fat body of Caradrina quadripunctatay in the 

 intestine and pupae of Pieris brassicae and Vanessa urticae and in the 

 excretion of newly moulted imagines. Manunta,^^ however, claimed 

 that both carotenes and xanthophylls occurred in the haemolymph and 

 hypodermis of P. brassicae, the relative amount of xanthophylls being 

 greater in the hypodermis. Later the same investigator indicated that 

 these carotenoids were a-carotene and taraxanthin. ^ ^ 



Gerould ^ ^ found that the colour of a blue mutant of the normally 

 green C olios philadice was due to the destruction of alimentary " xantho- 

 phyll " by the intestinal epithelium, thus unmasking the blue-green of 

 ** chlorophyll-a " in the haemolymph. The eggs of these insects are 

 also devoid of carotenoids. 



It appears that the clothes moth {Tineola biseliella) does not need a 

 dietary source of carotenoids, neither does it manufacture them on a 

 carotenoid-free diet. '' The skin of the larvae of Sphinx ligustri contains 

 lutein attached to a protein. ^ ^ 



The haemolymph of male Xanthia flavago is colourless, while that of 

 the female is greenish-yellow, owing to the presence of carotenoids. 



Metabolism 



The remainder of the work to be described in this section has been 

 carried out on the economically important silk worm, Bombyx mori. 



According to Geyer ^ * the sex difference in B. mori (males are colour- 

 less and females bright yellow), is due to the absence of carotenoids 

 from the male. The eggs contain carotenes and xanthophylls with the 

 xanthophylls in excess^* and the cocoons carotene and lutein^' 

 (xanthophyll) with free lutein the predominant pigment ^ * ; esterified 

 lutein and violaxanthin are also present. The pigments of the haemo- 

 lymph are similar to those of the eggs. Manunta ^ ^ showed there was a 

 differential distribution of carotenoids in the four layers of the cocoon 

 coat. As one moves from the outside inwards the carotene content 

 drops steadily, whilst the lutein content increases until it reaches a 

 maximum in layer III ; in layer IV it is slightly less. 



The factors producing yellow (carotenoid-containing) silk and white 

 silk have been studied. ^ • Ude ^ ' claimed that there are two genes 

 which control pigmentation of silk ; C determines that the blood 

 contains carotenoids and Y that these are passed on to the serigenous 

 glands. This view implies the possibility of the occurrence of insects 

 with yellow haemolymph and white silk (absence of Y) ; such have 

 been found, both by Ude himself and by Gerould. ^ * 



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