410 JOHN H. GEROULD 



probably acts primarily through the nuclei of the intestinal 

 epithelium upon the digesting chlorophyl, and thereby upon the 

 blood itself. It affects directly, or indirectly through the blood, 

 every stage in the life-history of the insect. 



9. The egg of the butterfly from a blue-green caterpillar is 

 pure alabaster-white, not the normal cream-white, an effect due 

 to the lack of yellow in 'the blood of the mother. 



10. The blueness of the blood of the larva becomes visible 

 just before the second molt by the stretching of the skin, then 

 relatively thick. After this molt the larva is conspicuously 

 bright blue-green ('light procelain green' of Ridge way). 



11. There are no intermediates. It is a sharply discontinuous 

 variation. 



12. The pupa is only slightly less blue than the larva. Its 

 cast cuticula is white, not the normal yellow. 



13. The wing color of the adult is unaffected by the mutation, 

 for females from blue-green caterpillars have either yellow or 

 white wing colors, as determined by another independent pair 

 of genes. 



14. The eye color of the adult is affected by the mutation, 

 probably through action of the blood. It lacks yellow and is 

 of a bluish green ('mineral green' rather than the normal 'apple 

 green'). 



15. The determination of the color of the hemolymph is 

 primary, or direct, but that of egg, pupal cuticula and of the eye 

 secondary, or indirect. The following observation favors the 

 idea that at the points last mentioned the action is indirect : 



16. Hymenopterous parasites, Apanteles flaviconchae Riley, 

 emerging from a grass-green caterpillar spin bright golden- 

 yellow cocoons, those emerging from a blue-green caterpillar 

 spin white cocoons. The lack of xanthojDhylloid pigment in 

 the blood of the blue-green host, or possibly the action of a yellow- 

 inhibiting enzyme produced by the gene in the blood, changes 

 the color of the secretion of the silk glands of the parasite from 

 yellow to white. Presumably, the blood affects in a similar 

 manner the hypodermis and cuticular secretion of the hypoder- 

 mal cells of the host. 



