346 
ZOOLOGICAL LITERATURE. 
(/. c. p. 263, and iv, p. 16), by J. B, Hodgkinson at Witherslack (Ent. M. 
Mag. iv. pp. 98, 137, & 154), by Blackburji at West Wic’ bam (1. c. p. 41), 
by Blackburn at Rannoch (1. o. pp. 138-139), by J. Sang, Microlejndopto'a, at 
Darlington (1. c. p. 163), and by W. H. Harwood near Colchester (/. c. p. 162). 
M^Lachlan, after noticing tlie variations of Sterrha sacrariuj 
discusses the phenomena of variation in the Lepidoptera in 
general (Trans. Ent. Soc. 3rd ser. ii. pp. 458-468) . He indicates 
that Britain is remarkable for the number of its varieties of Le- 
pidoptera, and points out a considerable number of cases in which 
the variation of the species seems to be in accordance with fixed 
and general rules. Thus numerous species (many of which are 
cited I, c. p. 459) become darker or melanised in the north 
of England and in Scotland; and the country about Warrington 
especially seems to be peouliarly favourable to the production 
of dark varieties, so that, as M ^Lachlan remarks, it is not diffi- 
cult to imagine that, should this district suddenly become iso- 
lated, these forms would of necessity develop into Avhat we should 
very fairly call species.^^ These and other examples are employed 
by M^Lachlan in support of a limited Darwinism. He thinks 
that ordinarily varieties have a tendency to revert to what we 
consider as the type, but that, under certain circumstances, not 
only will they not so revert, but that the divergence will gradu- 
ally become wider, until eventually they develop into what is 
considered as a species. With regard to the variation of lar- 
vae, which M^Lachlan considers to have little to do with that of 
the imago, he publishes a long and elaborate tabular statement 
from the observations of Hellins and Buckler, in which the food- 
plants and the variations of the insects in the larval and perfect 
states are clearly indicated. From this it would appear that 
larval variation is more common and extensive in those species 
which feed upon various plants, although these very insects are 
exceedingly constant in the imago-state ; and M^Laclilan is in- 
clined to regard the variation of the larvae, especially in those 
forms (such as many Eupithecice and other Geometridae) which 
feed on flowers, or at all events during the day, as an instance 
of mimicry destined to screen them from the attacks of birds. 
In the case of Eupithecia absinthiata he has noticed the varia- 
tion in the colour of the larvm as being distinctly in accordance 
with that of the different kinds of flowers on which they were 
feeding. M^Lachlan also refers to other peculiarities displayed 
by species of Lepidoptera in different British localities, espe- 
cially to the fact that many species which produce two broods 
annually in the south, have only one brood in Scotland, and to 
the circumstance that in the latter country some species re- 
main for two or three years in the pupa-state. 
The portion of M^Lachlan^s paper just noticed has been 
translated into French by Girard and Fallon, who also append 
some rather voluminous notes to it (Ann. Soc. Ent. Fr, 4® ser. 
