356 BRITISH LEPIDOPTERA. 



trace of the light transparent zone on the horns of i, 3 and 4. The 

 tip was slightly but distinctly bifid in all except 4 and 5. The spir- 

 acles were bright orange and extremely conspicuous in all the larvae. 

 (II) The four intermediate larvae of the 3rd stage. — These larvae were 

 of very uniiorm size on October 8th, being about 30mm. long. There 

 were faint traces of a bifid termination to all the horns except 

 that of 1 which was somewhat distorted. 



1. This larva was a green variety, but not so bright or with so much 

 oi the green colour as 1 of the previous division. There- was rather less green 

 on the head and much less along the median dorsal line. The green was duller 

 and less yellowish in tint ; the dark borders were much wider and were of con- 

 siderable breadth at the point where they became continuous with the black 

 dorsal band, whereas these two dark markings were almost discontinuous in 

 1 of the previous division, thus nearly allowing the subdorsal line to pass between 

 them. The transparent zone on the horn was slightly marked ; there was hardly 

 any of the reddish-brown colour at the base. This larva was carefully re-examined 

 on October nth, when nearly mature in this stage, and was again compared 

 with the lightest of the previous lot (shewn in pi. xvi., fig. 1); the larva formed 

 a beautiful but gradual transition from the latter in the direction of the darker 

 larvae. All the points in the comparison made above continued to hold at this 

 later date. It was also noted that the dark spiracular baud on the thoracic 

 segments was wider, and that the horn was blacker. The oblique stripes were white. 



2. A dark variety about equal to 4 of the previous lot. An exact com- 

 parison was very difficult, especially because of the change of colour during growth, 

 and also because the darkness varied in different parts of the larvae, so that extreme 

 darkness in one part might be compensated by unusual lightness in another. Thus 

 this larva retained the traces of the green ground-colour as in 2 of division 1 

 (fig. 3). Nevertheless the differences between the dark larvse were insignificant 

 compared with the differences between them and the green larva. There was no 

 trace of the transparent zone on the horn. 



3. A dark variety about equal to 5 of the previous division. The 

 ground-colour was dark, but the two longitudinal stripes were very distinct, and 

 the transparent yellow zone on the horn very conspicuous, but there was hardly 

 any reddish-brown colour at the side of the base. 



4. This larva was darker than any of the previous division. The transparent 

 zone on the horn was slightly marked. The larva is represented in pi. xvi., fig. 5. 



(Ill) The six darkest laivae of the 3rd stage. — Five of these larvae were 

 compared on October 8th, the 6th being still in the previous stage. 

 The lengths of the larvae are given below : 



1. The lightest larva was an extremely interesting green variety, transitional 

 from the 1st of the last division towards the dark varieties. It is represented in 

 pi. xvi., fig. 2 (x 2). Although much darker than either of the other two green 

 varieties, there was, nevertheless, a larger amount of green colour spreading from 

 the stripes. The reddish-brown patch at the base of the horn was very distinct 

 in this and the other four larva? of this division. This larva was about 27mm. 

 in length. 



2. This larva was about equal to the 5th of division I. Length 36mm. 



3 and 4. These larvse were very dark, but the two longitudinal stripes 

 were very distinct and of a bright yellow colour. The larvse would be classified 

 with No. 6 in division I, and their appearance is represented in pi. xvi., fig. 4. One 

 of these larvae exhibited no trace of a bifid extremity to the horn, which was 

 present in all the others of this division. Length of both larvae 36mm. 



5. This larva was equally dark and with longitudinal stripes less strongly 

 pronounced. It would be classified with the darkest larva— (4)— of division II, 

 and may be represented by the figure of the latter larva (fig. 5). The yellow 

 transparent zone on the horn was very distinct in this larva and 1, very slight 

 in one of the last two larvae, and absent from the rest. Length 30mm. 



The comparison between figs. 1 — 5 (pi. xvi) shows the chief 

 steps of the transition from the greenest to the darkest larvae, but 

 many intermediate steps are necessarily omitted. These are, 

 however, indicated in the tabular form given below, which sum- 



