Proceedings of the Royal Society of London Volume 38
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1885 edition. Excerpt: ...proper to the larvae, or larval tissues made use of because of some (merely incidental) aid which they lend to the colouring, e.g., fat. A larva may be coloured by either or both of these groups of factors. It may be generally stated that all green colouration without exception, as far as I have investigated the subject, is due to chlorophyll; while nearly all yellows are due to xanthophyll. All other colours (including black and white) and some yellows, especially those with an orange tinge, are due to the second class of causes (as far as I am aware: it is, however, extremely probable that certain colours will be proved to arise from the modification of the derived pigments; and many observations make it probable that other colours may be derived from plants in the case of larvae feeding upon the petals, &c.). The derived pigments often occur dissolved in the blood, or segregated in the subcuticular tissues (probably the hypodermis cells), or even in a chitinous layer, closely associated with the cuticle itself. This last situation has only as yet been proved in the case of the pupa of Papilio Machaon, but it is almost certainly true of many other pupae. The colours proper to the larvae occur in the hypodermis cells and in the cuticle. The commonest structural basis of variability or polymorphism in larvae is afforded by the varying extent to which either of these factors takes part in producing colouration. Thus brown and green are by far the commonest instances of dimorphism, and when this is the case the former is due to larval pigment, the latter to derived plant pigments. It is very remarkable that there should be such an essential difference between the l8J'Vae from the same batch of eggs, as far as the causes of colour...
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