1876.) . 147 



H. pisi (?) ; Larentia duljjmnta ; Agrotis nigricana * ; Noctua C- 

 nip-um. (The last three species ought perhaps to be included in 

 division 1). 



Besides the above, melanochroic forms of several other species 

 occur, but rarely, e. g. the green aberration of Tracliea inniperda. 



II. Leucochroism. 



1. Species of which all, or a majority, of the individuals are paler 

 than in the South. — Lgccena Agestis (var. Arfaxerxes, F.) ; Fldonia 

 piniaria (the type ; the yellow southern form is the Yar.Jiavescens) ; 

 Platypteryx falcula (var. pallida) ; Tceniocampa cruda. 



Reference may also be made to — Pararge u^gerla (in comparison 

 with the brighter-coloured South European form) ; and Cceno7iympha 

 Fampliilus (in comparison with the form Lyllus). 



2. Species frequently paler but not invai'iably so. — Ccenonympha 

 TipJion ; Chelonia plantaginis (ab. liospita, SchifE.) ; Cidaria corylata 

 (ab. alhocrenata, Curtis) ; Eup>itliecia satyrata (ab. callunaria, Stn.) ; 

 Noctua f estiva ; Tceniocampa gothica (ab. gothicina, PI.-S.) ; X.antliia 

 cerago (jah. Jlavescens, Esp.) ; Lithosia mesomella ; Venilia maculata ; 

 Cleora lichenaria (?) ; Leucania lithargyria (?). (The last four species 

 perhaps belong to division 1). 



It will be observed that many of the forms included in both 

 classes are not confined to the Highlands, but are found in Lowland 

 Scotland, and elsewhere. 



Of the melanic varieties mentioned by Mr. Birchall some, as 

 CymatopJiora diluta, Leucania pudorina, ^c, do not occur in the 

 Highlands, and therefore do not come within the range of my 

 remarks ; others, as Girrlioedia xerampelina, Folia clii, and Aplccta 

 nehulosa, do not show mclanochroism there : some, as Grocallis elin- 

 guaria, Hypsipetcs elutula, Larentia cccsiata, &c., might equally (or 

 nearly so) be cited as samples of leucochroism. Epimda lutulenta 

 (var. lunehurgensis) I rather consider as illustrating leucochroism 

 than melanochroism. Ilepialus J/umuli ab. hethlandica is a local 

 insular form, and not even I believe the predominating form in 

 Zetland. 



AV^e now come to the consideration of the cause of the prevalence 

 of melanochroism in the Highlands. 



]n suggesting "natural selection" as the cause, I believe tliat 

 Mr. Birchall has solved a great part of the difllculty ; not entirely 

 perhaps, for, considering all the facts, I still think there must be some 

 exciting cause (probably meteorological) for the first production of 



* The Southern fonu is the ab. or var. rulrricant, Esp. ; the dark form is the type.— F.B.W. 



