Notes in 1887 upon lepidopterous larve, dc. 595 
advantageous to the species,—that each variety becomes 
of especial advantage when a certain proportion between 
the numbers of the two forms is reached. Whatever be 
the advantage afforded,—whether it be that suggested 
in an earlier paper (Trans. Ent. Soc. Lond., 1884, 
pp- 50—56), or because of a difference in the times at 
which the two varieties respectively appear,—it is 
perfectly certain that the advantage is real. The 
breeding experiment with moths from larve of one colour 
clearly shows that if either form were less useful, it 
would be exterminated in a very few seasons. 
12. THE PROTECTIVE RESEMBLANCE OF THE PUPA OF 
APATURA IRIs.—During the past summer (1888) I suc- 
ceeded in obtaining a single fine female pupa of this 
species from larve sent me in the autumn of 1887, by 
George Tate. 
The pupa was suspended from a sallow-leaf, and it 
resembled a leaf in the most perfect manner. The 
twig of sallow was on several occasions offered to 
friends in order to ascertain whether they could detect 
the pupa, and it was almost invariably overlooked. 
Even when the pupa was pointed out, the observer 
frequently failed to see any difference between it and 
a leaf. 
The most extraordinary thing about this resemblance 
was the leaf-like impression of flatness conveyed by a 
pupa which was in reality very far from flat. Thus the 
length of the pupa was 30°5 mm.; the greatest breadth 
(dorgo-ventral diameter), 11°5 mm.; the greatest thick- 
ness (from side to side), 8°5 mm. The following notes 
were taken July 12th, 1888 :— 
The midrib of the supposed leaf is represented by a 
white line along the upper wing, corresponding to its 
upper edge posteriorly, but below the true edge 
anteriorly: in the latter region the midrib is repre- 
sented by a ridge (corresponding to the costal margin 
of the future imaginal fore wing), which extends along 
the (pupal) wing horizontally, and meets the antenna 
obliquely at the junction of the meso- and prothorax. 
Posteriorly to the upper wing the line crosses the 
exposed narrow strip of the hind wing, obliquely, on its 
way tothe abdominal segments, over which it is con- 
tinued backwards as a white stripe immediately above 
