1885.] Colouring of Phytophagous Larvae. 275 



blood. On the other hand there are larvae which entirely depend 

 npon the green blood for their colour, and there is a transparency 

 about such larvae which at once distinguishes them from those above 

 described. Thus green Noctua larvae are usually of this kind. 

 The species of Noctua which exhibits the most typically trans- 

 parent green (that I know of) is the larva of Gonoptera Libatrix 

 (although I have never investigated the constitution of the colouring 

 in this species). Again, pressure has a comparatively slight effect 

 upon the distribution of colour in larvae of the former division, while 

 it produces the greatest effect in those of the latter. I think it is 

 very probable that in many cases the derived pigments may only exist 

 in the blood in the early stages, and may be deposited later in the 

 superficial tissues. Such an arrangement would entirely accord with 

 a very common change in the appearance of green larvae during 

 growth. There is generally a marked difference in the colour of 

 a green larva after its first meal, and before this the transparency is so 

 complete that its tracheae and other internal organs can usually be 

 seen. But it does not therefore follow that the chlorophyll is at this 

 time deposited in the superficial tissues (although such may be the 

 case), for the facts may be accounted for by an increase in the amount 

 of colour in the blood, and by a change in its tint (the probability of 

 this will be shown presently). 



3. The Different Results of Methods of Preservation upon the two Factors 

 in Larval Colouration. 



The derived pigment can always be distinguished from that proper 

 to the organism, in larvae which have been preserved in spirit, or as 

 blown and dried specimens. After both processes the proper pigment 

 is unchanged, being quite insoluble in spirit and uninjured by drying. 

 The derived pigments, on the other hand, dissolve in the spirit from 

 the blood and from the superficial tissues, while in blown larvae the 

 blood is removed (with the other contents of the body), and the 

 chlorophyll in the superficial tissues rapidly fades, while the yellow 

 due to the xanthophyll may persist for a long time. Looking over a 

 dried collection, it is at once obvious that green larvae, such as 

 P. Bapa3, 8. Populi, 8. Tilice, Notodonta Camelina, &c, have entirely 

 changed in colour, while others, such as Liparis Auriflua, Bombyx 

 Neustria, Odonestis Potatoria, Eriogaster Lanestris, &c, remain 

 perfectly life-like. Hairy, brightly-coloured larvae are generally 

 unchanged, as also are those distasteful forms which are protected 

 by conspicuous colours (such as Abraxas Grossulariata, Euchelia 

 Jacobean, &c). Smooth brown larvae (such as the majority of 

 Geometers and many Noctuas) have evidently lost some depth of 

 colour, due to the removal of the contents of the body and the con- 



