﻿148 THE ENTOMOLOGIST. 



form represented by the blackish lower fourth only. These last 

 modifications of the stigmata are only observed in the pale 

 coloured specimens, and are generally associated with absence of 

 longitudinal and transverse markings. 



The claviform, sometimes not present in either species, is 

 usually outlined in black in tritici, and black or brown in 

 cursoria. In some specimens of each species it is large and well 

 defined, while in a few it is entirely filled up with black, and only 

 separated from a longitudinal black basal bar by the inner trans- 

 verse line. 



The pale colour on costal area has been referred to in these 

 notes as the subcostal streak, because it appears to be the ampli- 

 fication of a character which exhibits initial development on the 

 subcostal nervure. In some examples of cursoria from Unst, the 

 space between subcostal nervure and the costa itself is filled up 

 with white, and in these specimens the specific characters of upper 

 surface are of course hidden. 



THE USE AND ABUSE OF THE TBINOMLAL SYSTEM. 

 By Bichard South. 



To any who may be inclined to confer varietal names, the 

 numerous forms of Agrotis tritici and A. cursoria will afford 

 abundant material upon which they can operate with consummate 

 satisfaction to themselves ; but as I have yet to learn in what 

 way science in general, and that of Entomology in particular, is 

 advanced by the imposition of distinctive names on certain links 

 in the chain of an insect's variation, I have not ventured to take 

 upon myself the responsibility of adding some fifteen or twenty 

 names to the perplexing list of aberrations we already have. 



I am well disposed towards the trinomial system, as suggested 

 by Mr. Cockerell (Entom. xx. 150), but the most ardent supporter 

 of that system must take exception to the wholesale christening 

 of more or less unimportant aberrations. The lepidopterist is 

 well aware that with very many species, especially among the 

 Noctuse and Geometrse, there is a tendency to deviate either in 

 colour or markings, sometimes both, from a given type. In 

 some of these species aberration is often of a most extensive 

 character. The scheme of variation, however, is, with few 

 exceptions, identical throughout, i. e., there is aberration 

 (a) in colour, (b) modification of markings. As regards colour, 

 departure from a fixed type is exhibited in one of two opposite 

 directions, sometimes both : one graduates in the direction of 

 melanism, the other towards albinism ; whilst the ornamentation 

 may be well developed, and consequently conspicuous on the one 

 hand, or evanescent on the other. In a good series which really 



