INSECTS, ARACHNIDS AND REPTILES 



A possible function in reproduction is suggested by the presence of 

 carotenoids in insect eggs ; carotenes and xanthophylls in B. mori ^ *• * ' 

 and p-carotene alone in Melanoplus bwitattuSy » 3. » « Locusta migratoria 

 and Schistocerca gregaria. ^ ® Goodwin ^ * has shown that ^-carotene is 

 metabolized during development of eggs of Locusta and Schistocerca ; 

 at about the 6-7th day of incubation ^-carotene begins to disappear 

 and astaxanthin to appear {see Fig. 29). This production, in the embryo, 

 of astaxanthin may be to ensure that the newly-hatched hopper is well 

 equipped for vision, for Wald^^ beheves that photoreception is the 

 main raison d'etre of astaxanthin in invertebrates. If, however, a 

 sexual function is eventually assigned to insect carotenoids it cannot 

 be universal for, as has previously been stated, a number of insects 

 can develop normally without the aid of carotenoids. 



ARACHNIDS 



Heim**® found a pigment, probably a carotenoid, in a mite (Throm- 

 hidium) and according to Manunta * ^^ this is astaxanthin. 



Within the last few months, Beament ^^^ has found that the eggs of 

 the apple tree mite {Metatranychus ulmi) contains two carotenoids, the 

 minor component, about 10 per cent, of the total, is a-carotene, whilst 

 the other remains, at the moment, unidentified. Beament has also 

 shown that the rate of development after hatching is directly related to 

 the colour of the egg ; whether this has anything to do with the caro- 

 tenoid content remains to be seen. The summer eggs of M. ulmi are 

 normally orange, whilst the diapausing and winter eggs are bright red 

 and contain about three times as much pigment as the summer eggs. 



Hueck*^'^ has noted that blue light has a profound effect on the 

 hatching of the apple tree mite ; if this is confirmed, it may well be 

 that the carotenoids are the sensitizing pigments for this photo-action. 



REPTILES 



Although not closely connected with the animals discussed in the 

 previous section of this chapter, it will be convenient to consider here 

 the little that is known about carotenoids in reptiles. 



Kruckenberg and McMunn, during their pioneer experiments on 

 animal pigments, came to the conclusion that the fat-soluble pigments 

 of a number of snakes and alligators were not carotenoids 

 (lipochromes). ^ '^ On the other hand Kruckenberg®* did obtain 

 evidence of the presence of a hydroxy carotenoid in a number of 

 chameleons, viz.^ Lacerta muralisy L. agilis, Chamaleon vulgaris and 



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