286 Mr. E. B. Poulton. Essential Nature of the [Apr. 23, 



of the blue end 48 — 51, the second band of the blue end 45 — 4675, 

 the violet being absorbed at 41. The second band of the blue end is 

 much fainter than the first band, and it is not seen in a thickness 

 of 5 mm. 



(c.) The Pupa of S. Tiliae. — The blood was very bright green and 

 perfectly clear. A thickness of 5 mm. was examined with the light 

 of a paraffin lamp. The spectrum showed a very broad band in the 

 red from 64*5 — 70, while the red and orange were much dimmed. 

 The violet end was absorbed to 50, dimmed to 51, and no blue came 

 through on widening. The green was the only part of the spectrum 

 which was not dimmed. A thickness of about 1 mm. gave the band 

 in the red from 66 — 69 (but the limits were very difficult to ascertain 

 exactly), and the violet end was absorbed to 49, darkened to 51, while 

 the blue came through on widening. 



(d.) The Pupa of S. Populi. — The blood was examined by the light 

 of a paraffin lamp, in a thickness of 5 mm. The colour was bright 

 yellowish-green. The spectrum showed the broad band from 66 — 69, 

 while the violet end was cut off at 51, darkened to 52. No blue came 

 through on opening the slit (with this source of light). 



(e.) The Pupa of S. Ocellatus. — The blood is of a bright yellowish- 

 green colour (rather pale). I have examined many specimens by sun- 

 light. A thickness of 4 mm. shows traces of the band in the red, and 

 with great care and the right conditions of light, gives three bands in 

 the blue end as well as an absorption of the extreme end. The chief 

 band is from 48 — 50*3, the second from 46*75 — 45, and the third, 

 which is very faint (and best seen when the slit is widened until the 

 violet is absorbed at 41), occupies 43 — 42. With less thickness the 

 characteristic band in the red disappears, while with greater thickness 

 it becomes very distinct. After adding absolute alcohol to the blood, 

 a bright yellow solution of xanthophyll was obtained, which gave 

 the characteristic spectrum (shifted to the violet) 49 — 47, 45*25 — 44, 

 the violet being absorbed at 42. 



(/.) The Pupa of S. Ligustri. — I have also examined the blood of 

 many individuals of this species by sunlight. The colour is a slightly 

 greenish-yellow in individuals that have fed upon lilac in the larval 

 state, yellow in those that have fed upon privet. The spectrum is 

 marked by very slight effects at the red end, but very powerful 

 absorption of the violet. In a thickness of 35 mm. the absorption in the 

 red was strong, but did not approach that of a thickness of 23*5 mm. 

 of the P. Bucephalus, although the absorption of violet was much more 

 complete. The spectrum of this thickness of the blood of S. Ligustri 

 is shown in the Chart, Spectrum 2, whilst Spectrum 3 is the Buce- 

 phalus blood which contrasts with it very markedly at both ends of 

 the spectrum. The characteristic band is seen to extend from 70 

 (ending sharply) to 64*5, becoming gradually continuous with a less 



