566 Notes in 1887 upon lepidopterous larvae, cc. 
figured in Plate XVII., fig. 5, is rather larger, being 
45°5 mm. in length). The 4th stage generally lasts 
from ten to twelve days, and the whole larval life, from 
hatching up to the change of colour before pupation, 
occupies from forty-two to forty-four days, although 
in some cases it may continue two or three days longer. 
I have already shown that the markings of the mature 
larva can be plainly seen upon the homologous parts of 
the freshly-exposed and still undarkened pupa (see 
Pros. Roy. Soc., Vol. XXXVIII., p. 278). These mark- 
ings form, in fact, a valuable guide to homologies. In 
the green, freshly-exposed pupa of Aglia tau, all the 
markings of the larva are very distinct, and the sub- 
spiracular line which forms so prominent a feature of 
the larva, and which is continued along each side of the 
anal flap to its extreme apex, is equally conspicuous in 
the pupa, and occupies an identical position in relation 
to the terminal anal spine, which in this species is blunt 
and covered with an immense number of irregular hook- 
like cuticular processes. Hence the position of the 
marking affords valuable confirmation of Mr. W. H. 
Jackson’s identification of the anal flap of the larva, 
with the anal spine of the pupa. (See ‘ Forms of Animal 
Life,’ by G. Rolleston and W. H. Jackson, 1888, p. 153). 
The shape and texture of the rough, dark pupa in this 
species, also strongly suggests that of Smerinthus populi, 
but its affinities are evidently still closer to the pup of 
Endromis and Saturnia, inasmuch as one unique (as far 
as | am aware) anatomical point unites together the pupz 
of these three genera—viz., the situation of the first or 
prothoracic spiracle at the bottom of a comparatively 
shallow pit, so that the spiracle itself is distinctly 
visible. In all other pupe with which I am acquainted, 
this spiracle is deeply placed at the end of a channel, the 
external end of which is often closed, and when open is 
sometimes defended in a special manner. When the 
mouth of the channel is closed, there is generally the 
indication of a former opening in the sculpture or shape 
of the pupal surface at this point. 
Conclusions.—It will be well to shortly review this 
most interesting ontogeny, and to summarize the points 
of resemblance between the larve of Aglia tau, and 
those of Sphingide, also calling attention to anything 
which is peculiar to the former. 
