INTRODUCTION. VI f 



in most instances, not only great variation in markings, but a most 

 extreme range of colour variation. 



Probably, extreme colour variation in the same species is more 

 strikingly exhibited among the NOCTUJB than in any other group. 

 Bryophila perla var. pallida is in its extreme forms almost white, var. 

 suffusa is frequently almost black, whilst var. flavescens is often of a 

 bright orange. Miana bicoloria varies from pure white to deep 

 brownish or rusty-fuscous and bright red. Xylophcutia polyodon from 

 pale greyish-brown, with white markings, to the most intense black. 

 The same range of colour extends through Viminia rumicis, Nonagria arun- 

 dinis,Luperina testacea,Apdmea basilinea,A. didyma, HelotropJta leucostigma, 

 Miana strigilis, Grammesia trilinea, Agrotis corticea, A. cinerea, Noctua 

 glareosa, Tceniocampa opima, Epunda viminalis, Aplecta nebulosa, and 

 others, although the extreme black forms may be tinged with reddish 

 in some of these species ; Agrotis tritici and Tceniocampa instabilis not 

 only exibit this range of variation (from the palest grey to deep black), 

 but each has beautiful slate-coloured or bluish varieties as well. 

 Xylophasia rurea var. argentea is pure silvery- white, var. nigro-rubida 

 intense reddish-black ; Anchocelis pistacina goes through a similar 

 range. Most of the Leucanidce vary from whitish (in some instances 

 pure white) to the deepest red, in some species even to black. The 

 group can hardly be left without casually referring to the wonderful 

 colour variation which exists in our Scotch specimens of Triphcena 

 orbona (comes as it is sometimes called), the specimens from Forres 

 and Aberdeen, varying from the palest grey to brilliant red, and 

 intense black. In fact, there is probably a larger proportion of species 

 presenting extreme colour variation in this group than any other. 



Size variation is frequently most marked. It may be due to 

 sex, or to environment, or there may be no very clear reason by which 

 such variation may be explained, Generally speaking, however, I be- 

 lieve, when variation in size is not sexual, that specimens which are 

 above the normal size have had a bountiful supply of nutritious food, 

 while those below the normal size have had an insufficient or innutri- 

 tious diet. That this is so, when insects are artificially reared, is beyond 

 question, and it is only reasonable to suppose that one foot-plant, less 

 nutritious than another, would, if it were the staple food in a district, 

 produce specimens below the normal size. In insects, as a rule, 

 females are larger than males, but this is not always so. Often among 

 the NOCTILSE, the opposite is the case, striking examples existing in 

 Chortodes arcuosa, Nonagria rufd, Hydrilla pafastris, Eusina tenebrosa, 

 Agrotis cinerea, Acosmetia caliginosa, Stilbia awoma/aand Noctua umbrosa. 

 But, generally, the great mass of the NOCTUA follow out the ordinary 

 rule, or there is very little to choose in size between the sexes. Certain 

 localities often give us large or small races* of special insects. The 

 normal size of Agrotis valligera and A. tritici from Sligo, is less than 

 that of the specimens of the same species from Deal ; Asphalia flavicornis 

 from Scotland is normally larger than are those from Kent ; Luperina 

 testacea is very large at Freshwater in the Isle of Wight ; Noctua 

 f estiva is normally smaller from Aberdeen than are those from Kent; the 



*The most striking examples of variation in this direction exist among the 

 GEOMETRY, e.g. Aspilates strigillaria, Hypsipetes elutata, and above all Thera 

 juniperata, and its var. scotica. 



