92 NATURE 
colour of the more stable pigment—xanthophyll—preponderates 
cover the green of the metachlorophyll in the newly-hatched 
larva. The bands of xanthophyll are distinctly seen in an 
alcoholic extract of crushed ova taken from the bodies of moths 
which have been preserved for ten years or longer. In blown 
and dried larvee the greens soon fade, while the yellows persist 
and the pigment can be detected after many years. The true 
pigments are also unaltered. In larvae preserved in spirit the 
derived pigments quickly disappear, and the alcohol is yellow 
with xanthophyll, while the true pigments are unchanged. 
These facts are also true of phytophagous hymenopterous larvae, 
as well as in the lepidoptera. Thus in Mematus curtispina the 
green colour is due to derived pigment, while the broad white 
dorsal band is due to fat collected on each side of the dorsal 
vessel (and it can be seen to move with the pulsations of the 
latter). In Cresus Septentrionalis fat becomes the vehicle for a 
yellow colour. The few exposed pupz of moths are coloured in 
the same manner as the larve (4.9. the Zphyride and E. angu- 
laria). In the Ephyrids, dimorphic larvee—green and brown— 
produce pupz which follow the colour of their respective larvee. 
Larval markings can often be seen upon the pupa immediately 
after pupation. Thus the pupa of Sphinx ligustri is marked hy 
the oblique stripes of the larva. The pupz of butterflies are 
nearly always protectively coloured, and often possess the derived 
pigments. In Pupilio machaon the derived pigments of the 
pup are segregated in a very remarkable chitinised (?) sub- 
cuticular layer, which is quite opaque, so that no effect is pro- 
duced by the bright yellow blood (xanthophyll). 
Methods of Investigation and Spectra of derived Pigments.— 
Zeiss’s micro-spectroscope was always employed, with bright 
sunlight as the means of illumination. The blood is obtained 
by pricking the pupa or the larva in some situation remote from 
the digestive tract. Existing under pressure, most of the blood 
at once emerges as a clear bright green or yellow liquid (when 
the derived pigments are present). It is received into a tube- 
section, with one end cemented to a glass slide, and when full a 
cover glass is placed upon the open end, becoming fixed by the 
drying of the blood. In most cases the blood so prepared will 
keep for months. The spectrum of metachlorophyll is as 
follows (in the case of the bright green fresh blood of the pupa of 
Pygaera bucephalus in a thickness of 23 mm.) :— 
Chief band in the red, 71*—65°, continuous with a less ab- 
sorption extending to 58°, darkest from 58°5—59°5; a broad 
band from 52°—48° with the dimmed blue and violet coming 
through 48*— 42°, from which latter point the violet end is 
absorbed. There is no absorption of the extreme red. A Zeiss’s 
scale is adopted in waich r*=1/100,000 mm. 
Comparing this spectrum with that of true chlorophyll, as seen 
in two fresh calceolaria leaves, the whole spectrum is shifted 
towards the violet end in the latter case, with the exception of 
the end absorption, which extends to 43°. The chief band in 
the red is 70°—64°5, and then the continuous absorption of 
metachlorophyll is replaced by two bands: 61°— 63° and 57°5 
—6o0°, and if anything the former is the darker, The broad 
band is 47°5— 51°, and the dimmed blue and violet 47°5 — 43°. 
The chief difference is the continuity of the three bands of the 
red end in metachlorophyll, and the fact that their darkness is in 
the order (1) (3) (2) from the red, instead of (1) (2) (3). A 
similar spectrum (as far as it could be identified by the use of a 
paraffin lamp) was observed in a clear green fluid from the 
digestive tract of the larva of Phlozophorx meticulosa. In 
yellowish green blood (pupa of S. Zéyustv7) the absorption at the 
violet end is aided by the xanthophyll present, which gives two 
bands if the thickness of blood be sufficiently small. In some 
cases a third band is also present. Thus the blood of S. légustrz 
in a thickness of 3mm. does not give the band of chlorophyll in 
the red, but shows three bands in the more refrangible half of 
the spectrum: 48° - 50°, 45°— 46°25, and 42°— 43° the violet end 
being absorbed at 41°. Between these areas of absorption the 
spectrum is dimmed. The three bands become less distinct in 
the above-mentioned order, and the third can only be seen under 
favourable conditions of light, and appears to be absent in some 
cases. Mr. Sorby states that a third band, due to another sub- 
stance, is sometimes present in the xanthophyll spectrum. While 
the spectrum of metachlorophyll is very constant over a large 
number of larve and pup, in the living green pupa of Zphyra 
punctaria, a form of chlorophyll with a rather different spectrum 
was met with, in which the second band of true chlorophyll is 
present instead of the continuous absorption, while the third 
band could not be seen in the slight thickness obtainable. The 
[May 28, 1885 
term ‘‘ephyra-chlorophyll” is given to this pigment, which is 
dissolved in the blood of the pupa. Metachlorophyll, and 
probably xanthophyll, are united with a proteid in the blood. 
The addition of ether to green blood brings down the combined 
pigment and proteid in the form of a green coagulum, from 
which the ether does not dissolve the metachlorophyll, but 
gradually takes up the xanthophyll, becoming bright yeliow. 
Alcohol, on the other hand, decomposes the combined proteid 
and pigments, the coagulum rapidly becoming decolorised, and 
the xanthophyll passing at once into solution, while the meta- 
chlorophyll disappears. Hence it seems that the latter pigment 
depends upon its association with the proteid for its extreme 
stability and permanence under the action of light. This per- 
manence is necessary for the larva, since any colour due to 
derived pigments implies the penetration of light, and often the 
complete translucence of the whole organism, and, further, there 
are long periods (at the ecdyses), during which the pigments 
cannot be renewed, because no food is taken, Then there are 
the extreme cases of the green Ephyra pupz, and the green 
pupe of P. machaon, freely exposed to daylight during two- 
thirds of the year. It seems certain that the derived pigments 
are merely protective, and are of no further importance in the 
physiology of these organisms. Thus it is not probable that 
there are any marked differences between the physiological pro- 
cesses of the green and brown larve from the same batch of 
eggs, or in the processes of a green larva which has become 
brown, or vice versd. The blood of larvz seems to be always 
acid (and so with all pup examined, except 2. punctaria, of 
which the blood was neutral, in the only instance in which the 
blood of this pupa was tested), but I have as yet been unable to 
obtain a sufficient quantity of blood to determine what acid is 
present. The blood forms a solid, black coagulum which is due 
to oxidation, and does not take place when the blood is preserved 
in the manner described above. The injured parts of larve 
which have healed are black. It is probable that the darkening 
of pupze and of the cuticular pigment of larvee is also due to oxi- 
dation. There is great variability in the amount of clot formed 
and in the rapidity of the process. 
Historical.—Mr. Raphael Meldola, in the Proc. Zool. Soc. for 
1873, and in the editorial notes to his translation of Weismann’s 
«Studies in the Theory of Descent,” Part. II., ‘‘ On the Origin 
of the Markings of Caterpillars,” &c., argues very convincingly 
for the use of plant-pigments by green larvee. He points out 
that internal feeders are never green unless their food contains 
chlorophyll, and that when this is the case (Wefticula oxyacan- 
thella, &c.) they may be green, although the colour cannot be 
of any advantage to them. Pocklington (confirmed by Dr. 
MacMunn) found chlorophyll in the elytra of Cantharides, and 
Chautard seems doubtful about the same pigment in this situa- 
tion (Compt. Rend., January 13, 1873, and Ann. Chim. Phjs., 
5, lii., 1-56). Dr. MacMunn found a band in the red which 
resembled chlorophyll, by concentrating light on the integument 
of the larva of Preris vase and examining with a micro-spectro- 
scope ; but both he and Krukenberg refer the pigment to the 
larval digestive tract. (See Meforts of British Association 
at Southport, 1883, and a letter by Dr, MacMunn to NATURE 
for the week ending January 10, 1885). It is very unlikely that 
the green colour of so thick and opaque a larva can be due to its 
digestive tract, and it is probable that the blood, with its dis- 
solved metachlorophyll, was lost in the manipulation, From 
memory of the appearance of the larva, and from examining a 
blown specimen, I should certainly infer that there are also 
derived pigments in the subcuticular tissues. 
The Relations between the Colour of Phytophagous Larve and 
that of their Food-Plants.—Entomologists have been long aware 
of the fact that the colours of many larvee vary (within the 
limits of the same species) according to the colour of the plant 
upon which they are found. Complete references to the obser- 
vations hitherto recorded upon this point occur in Mr. Meldola’s 
writings (mentioned above). Among the most important of 
these is a paper by Mr. R. M’Lachlan (Zyans. Ent. Soc , 1865, 
p- 453) in which data are given as to Lupithecia absynthiata, 
which were yellowish when found upon Senecio jacobea, reddish 
upon Centaurea nigra, whitish upon Matricaria. When nearly 
full grown they were all given Sevecéo jacobea without altering 
the colour of the reddish and whitish varieties. From this Mr. 
M’Lachlan argued (1) that it was necessary for the larvee to have 
fed on the one kind of plant from the egg to acquire the resem- 
blance ; (2) that the colour is not caused by the food showing 
through the somewhat transparent integument. Mr. Meldola 
—— 
