Variation in Lepidoptera. 467 
to a naturalist holding the one view as to another who prefers 
to adhere to old ideas; it is only that the one looks upon the 
origin of that species in a different light from the other. 
I must ask my readers to bear with me for one moment whilst 
I diverge from the Lepidoptera to refer to another Order to which 
I have paid more particular attention—the Neuroptera. It is a 
fact that cannot be too strongly insisted upon, that in this Order, 
the secondary or auxiliary sexual appendages present almost 
infallible characters for the separation of species. Were these 
characters perfectly infallible, were there not some forms in a tran- 
sitional or variable condition, this would, I consider, be fatal to 
the ‘development ” theory, but such forms or species do exist, 
and, for instances, I refer to De Selys Longchamps and Hagen’s 
** Monographie des Gomphines,” in which it is shown that in two 
species at least, Gomphus (Onycogomphus) forcipatus (pp. 28-40, 
pl. ii.) and Cordulegaster annulatus (pp. 333-837, pl. xvii.), the anal 
appendices present rather remarkable variations in form accord- 
ing to locality, and, perhaps, correlated with certain differences in 
coloration. I have no doubt that other instances could be cited, 
and I believe that even in the T’richoptera parallel cases may be 
found. 
In bringing these notes to a close I must glance at a very 
elaborate paper “ On phytophagic Varieties and phytophagic 
Species,” by Mr. Benj. D. Walsh, of Rock Island, Illinois (a 
writer thoroughly imbued with Darwinian views), published in the 
Proceedings of the Entomological Society of Philadelphia, vol. 1. 
pp. 403-430. In this paper he classes variation by food under 
twelve different heads (pp. 427-428), which are. too lengthy to 
reproduce here. So far as I understand him, Mr. Walsh is also 
opposed to the notion of food being an immediate cause of varia- 
tion’in the imago, but he argues that in some insects there are cer- 
tain more or less constant forms attached to particular plants, and 
as a rule breeding only inter se, which are very closely allied, and 
which he considers as only phytophagic species, but, nevertheless, 
quite worthy to be considered and named as distinct. Under this 
rule would come many of the British species of Micro-Lepi- 
doptera,* and I fancy that had Mr. Walsh been extensively ac- 
* In the genera Gelechia, Elachista, Lithocolletis, Nepticula, &c., there are 
certain groups of closely-allied species, each of which apparently feeds exclu- 
sively on different species of the same family of plants. In Lithocolletis this 
is especially noticeable in the group of species (L. pomifoliella and its allies) 
attached to the fruit-bearing Rosacee. On the contrary, we often see totally 
distinct species of one genus living side by side in the same leaf. I wish to 
