CAROTENOIDS 



coloration except in mature males and, in the case of Schistocerca, to a 

 limited extent in hoppers. The green pigment occurring in the integu- 

 ment of solitary locusts is a typical insectoverdin as described by 

 Junge. ^ ^ It consists of a yellow and a blue component, the yellow 

 component is a caroteno-protein complex (containing both astaxanthin 

 and p-carotene) whilst the blue component is a chromoprotein con- 

 taining mesobiliverdin as its prosthetic group. ^ • The green haemo- 

 lymph of solitary locusts (gregarious haemolymph is golden) is also due 

 to an insectoverdin but this differs from that of the integument in that 

 astaxanthin is absent from its yellow component. ^ " 



In gregarious locusts, although astaxanthin and p-carotene are still 

 present, mesobiliverdin is absent, and the carotenoids are generally 

 masked by either melanin or insectorubin. * ^ Only in male adults do 

 they play a major part in gregarious coloration ; by migrating from 

 the subcutaneous tissue into the cuticle they confer on the insects a 

 yellow appearance. Similarly, the yellow coloured areas of the abdomen 

 of the Schistocerca hoppers is produced by cuticular p-carotene. 



Neuroptera 



The only report concerning insects of this group is that by Okay. " ^' ^ ^ 

 The green spring pigment of Chrysopa peila consists of two components 

 one blue and the other yellow ; the yellow is considered to be a 

 caroteno-albumin. 



The qualitative distribution of carotenoids in insects is given in 

 Table 40. 



FORMATION IN INSECTS 



Most of the work on carotenoid metabolism in insects indicates 

 that they accumulate their carotenoids in one of three ways : — (1) 

 indiscriminate storage of dietary carotenoids, (2) the preferential 

 storage of one or two dietary carotenoids, and (3) the alteration of 

 absorbed dietary carotenoids before storage. 



A number of examples of the first two processes have been cited in 

 the preceding sections, although it should be noted that opinion is not 

 always unanimous as to which process occurs to some species {e.g., 

 Pieris brassicae). Locusts are an interesting example because processes 

 (2) and (3) occur together ; p-carotene and astaxanthin are stored in 

 the various organs but plant xanthophylls never appear. The precursor 

 of astaxanthin is unknown but is quite likely p-carotene, for in the 

 developing egg, the appearance of astaxanthin parallels the disappear- 

 ance of (3-carotene. Further evidence that p-carotene is the precursor 



222 



