INSECTS, ARACHNIDS AND REPTILES 



to eat, remains steady through the various hopper stages and increases 

 considerably during adult life (Fig. 28). When the amounts of the 

 pigments per insect are considered, the carotene content continues to 

 increase throughout life, whilst that of astaxanthin becomes stationary 

 after the fifth hopper stage. The reason for these variations have not 

 yet been ascertained. 



During incubation of locust eggs the ^-carotene disappears and 

 astaxanthin is formed (Fig. 29). This is further evidence that p- 

 carotene is the precursor of astaxanthin in locusts {see also p. 219). 



Variation of breeding temperature of locusts, which has a consider- 

 able effect on the production of other pigments, has little effect on 

 the accumulation of carotenoids. * ^ 



4 6 



Days after laying 



hatched 

 unfed 



Fig. 29. — Carotenoid metabolism in the developing locust egg (fron) Goodwin, 

 T. W. {1949) Biochem. J., 45, 472). 



Carotenoids and phase transformation in locusts. When locusts 

 swarm, i.e.y change from the solitary to the gregarious phase, they 

 undergo marked colour changes ; these -have been recently described 

 in detail, *®'^° suffice it to say here that the most marked change is 

 the loss of the green pigment, characteristic of the solitary phase, and 

 its replacement by a much darker coloration. 



Although the gross carotenoid metabolism is not different in the 

 two phases, these pigments play an important part in the coloration 

 of the green solitaries, whilst they play no part in the gregarious 



221 



