The Scottish Natttralist. 
169 
tained in it, but from its popularity with collectors, affords ample 
material for the study of variation. 
In the text of his book Mr. Tutt does not enter upon the subject 
of the cause of the varieties, but in the introduction he refers 
briefly to some theories thereon; and in a series of articles 
on " Melanism and Melanochroism " in " The Entomologists' Re- 
cord " he has discussed at considerable length one aspect of it. 
The chief feature of " The British Noctuae and their Varie- 
ties " is the careful manner in which all marked variations 
from the type of each species are described. There seem to be a 
few species — but a very few — in which there is scarcely any 
variation. On the other hand there are some which are quite 
protean in their inconstancy of coloration and markings. Taking, 
however, the majority of the species, the rule seems to be that 
each has several well marked varieties. Although the main ob- 
ject of the book is merely the discrimination of the varieties which 
exist, and not a discussion of their distribution (though localities 
are often mentioned) or origin, yet a study of it will show that in 
the NoctucB^ just as in other animals and also in plants, some 
variations have intimate connection with the localities they in- 
habit, and hence — it may be supposed — have the cause of their 
origin in the conditions which surround them — in other words, 
their environment. 
In many cases British specimens are somewhat different from 
Continental examples of the same species ; and specimens from 
South Britain differ from North British ones. As a rule, though 
by no means invariably, there is a tendency in the latter to 
melanochroism or melanism, but in some species the very opposite 
is the case. 
Amongst the Noctuce, there are. according to Mr. Tutt, three 
modes of variation : (i) in general coloration, (2) in the markings 
of the wings, and (3) in the size and shape of the insect. All 
these may be combined in one specimen. 
Although Mr. Tutt calls all forms which differ distinctly from 
the type " varieties," it is evident that all the forms so designated 
are not of equal value or rank. Staudinger's division of forms 
into "varieties " and "aberrations," seems to be a preferable mode of 
classification, but doubtless Mr. Tutt has reasons for the plan he 
has adopted. 
An " aberration " is a varietal form which occurs along with the 
