CAROTENOIDS 



Manunta** has shown that the carotenoid concentration in the 

 serigenous glands increases with maturity ; this is accompanied by a 

 corresponding drop in haemolymph concentration. The amount of 

 pigments concentrated in the glands is not dependent on the maximum 

 levels attained in the haemolymph but on the efficiency with which the 

 carotenoids are transferred to the glands. This efficiency is primarily 

 controlled by the permeability of the gland to carotenoids, although 

 the rate of movement of pigment from the intestine to the haemolymph 

 is also of importance. According to Manunta^^ Philosamia ricini (eria 

 silk moth) larvae absorb only p-carotene and violaxanthin from the 

 complex mixture of carotenoids which occur in the leaves which they 

 eat ; furthermore, they seem to concentrate the (3-carotene in the skin 

 and the violaxanthin in the intestinal mucosae. On maturation, carotene 

 makes its way via the haemolymph to the intestinal mucosae of the 

 pupae. 



Hemiptera 



Two of the most interesting reports of investigations into the caro- 

 tenoids of this group concern the predaceous Perillus bioculatus^ and 

 the parasitic Apanteles flaviconchae. The former obtains its (3-carotene* 

 by sucking the haemolymph of the larvae and adult potato (Colorado) 

 beetle, Leptinotarsa decemlineata, which obtains its carotene in the first 

 place from potato leaves. * A. flaviconchae normally feeds on the green 

 larvae of Colias philadice from which it obtains xanthophylls for 

 excretion in the yellow silk with which it spins its cocoons. When fed 

 on the blue-green mutant of C. philadice from which xanthophylls 

 are absent {see p. 215), the resulting cocoons are quite colourless. ^^ 

 P- Carotene appears to be the only carotenoid present in Apis gossypii, 

 and it is interesting to note that there is as much ^-carotene in the 

 green as in the yellow forms. ^ 



Lederer^' has re-examined Pyrrhocoris apetrus which since 1894 

 has been known to contain carotenoids ^ ° ; somewhat surprisingly the 

 carotene present was identified as lycopene ; p-carotene was not 

 present. 



Recently Okay^^ has claimed that the green wing pigments of 

 Nezara viridula and A^^. viridula var. torquata are two component 

 systems. One component is yellow — a carotenoid-protein complex and 

 the other is blue. No free carotenoids could be detected in the wings ; 

 the identity of the blue pigment is obscure. 



Knight '1^ found that in hemiptera the carotene content of the 

 hypodermis was increased in insects reared at low temperatures and 



♦ It is not certain that this pigment is p-carotene {see p. 214). 



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