Ultimately this yellow colour, very pronounced in the males and only slightly 

 in the females, resembles exactly the normal maturation colour. 



The same relation between C. A. and yellow colour is revealed in an experi- 

 ment in which allatectomy is carried out on Vth stage larvae. After the final 

 moult normal adults appear which however never turn yellow at all, while 

 the control animals do in about 10 days. 



There is a certain similarity between the reaction of larval and adult pigmenta- 

 tion on the presence or surplus of C. A. hormone. Both phenomena may 

 have in common the yellow carotene component of the green blood colour 

 (Goodwin, 1952). On the other hand it is remarkable that under natural 

 conditions green colour in the larvae only appears under the absence of gre- 

 garious stimuli, while the yellow maturation colour in males only appears 

 under gregarious stimulation. 



2. Implantation of C. A. Substitution of the own С A. of a stage II larva 

 by adult C. A. reveals no appreciable difference between the activity of extra 

 implanted and substituted C. A. In both cases the further development 

 during the nymphal stage is quite normal. The larvae turn green as a rule. 

 In the last moult very often metathetehc characters (retaining of larval 

 wings, hairs, pigmentation) appear. From these and other observations can 

 be deducted that the innervation of the C. A. is not essential for the secretion 

 of hormone. Normal development in these cases is apparently dependent on a 

 constant or at least cyclic functioning of the implanted С A. When a substi- 

 tuted C. A. is removed again in a young larvae after the change to green colour, 

 this colour starts to disappear immediately and prothetely occurs after the 

 next moult. 



The role of the nervi corporis allati may be: 



1. Trophic action upon the gland. 



2. Inhibition of secretion in the Vth instar. 



The former activity is revealed by intersecting the nervi С. A. in larvae II. 

 This results in normal Ilird and I Vth stages but mostly the Vth stage is prothelic. 

 Dissection shows that the size of the C. A. did not increase any more after the 

 operation. Presumably the hormone production could not meet the demand 

 but did not stop completely for many of these prothetelic Vth stage larvae 

 turned more or less yellow later. 



Cross-wise implantation of C. A. of other locust or grasshopper species 

 succeed as well. Their effect seem to depend only on the specific size of these 

 С A. So adult Romalei C. A. as well as adult Locusta С A. substituted in Und 

 stage larvae are sufficient for a normal development. These С A. can be used 

 several times in succession for implantation in larvae and the results are the 

 same although activity sometimes may decrease in following passages. Up to 



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