Xll INTRODUCTION. 



connection between this peculiar grey, yellow and orange, is to be 

 noticed in nature in Litliosia griseola and its var. strammeola, in the 

 sexual dimorphism exhibited by L. quadra, and in the many different 

 varieties of L. pygmceola. All these show their direct derivation and 

 are very unstable. I have a perfectly white (bleached) female 

 specimen of L. quadra, and the grey of the male bleaches just as 

 readily. 



Among the NOCTUJE it is easy to prove the close connection 

 between white, yellow, red and brown. The various species of Len- 

 cania and Nonagria, whatever their typical colour in England, almost 

 invariably exhibit this range. For example, I have Leucania pollens 

 and L. straminea running from pure white, through ochreous, to deep 

 red, and there is a red tinge on certain specimens of all the species, 

 and sometimes this culminates in deep red -brown as in varieties of 

 Nonagria arundinis. The deep red (in England) of L. turca becomes 

 normally yellowish in Japan, and so on through many other species. 

 The yellow streak in Orthosia macilenta is frequently red, and some of 

 the dark chestnut coloured varieties of Orrhodia ligula (spadicea) and 0. 

 vaccinii have a broad subterminal band of yellow which is frequently 

 merged in the ground colour, the change from yellow to brown being 

 absolute. Similar variation occurs in the subterminal band of Bombyx 

 quercus. The almost absolute and identical nature of brown and red, 

 is well illustrated in species normally ochreous and varying to decided 

 red and brown tints as in Anchocelis pistacina, Orrhodia vaccinii, Tcenio- 

 campa stdbilis, T. munda, A. lunosa, Noctua castanea, N. festiva &c., 

 and still more strongly by the interchange of orange-red and brown 

 in the coloration of Anger ona prunaria. I have also a deep brown 

 variety of Himera pennaria and have seen distinctly red forms, whilst 

 the pale ochreous areas in the wings of $ Hemerophila abruptaria are 

 changed directly into brown in the male, the latter sex again appearing 

 to be the more highly developed form, whilst a pure yellow variety of 

 the normally brown Odontopera bidentata, which I possess, would 

 appear to point to a retrogressive condition, whilst bearing out at the 

 same time the general principles involved. I think, therefore, we may 

 safely assume that brown is directly developed from yellow, as also is 

 red, sometimes, but not necessarily, using red as a stepping-stone in 

 this direction of development. Agrotis cursoria and A. tritici are other 

 species which have distinctly reddish-brown and ochreous forms. 



If we wish for a direct proof that brown is convertible into yellow, 

 we have only to treat a number of brown species with hydrochloric 

 acid, ammonia and other ordinary reagents. Argynnis paphia and 

 other species of the same genus, Ccenonympha, Satyrus, Epinephele &c., 

 are all more or less rendered yellow, as also are the brown species of 

 Hesperia (sylvanus, linea &c.), and the species of Melitcea. Not that 

 these are all acted on uniformly by the same reagent, but some one or 

 other common reagent will reduce the brown to yellow, and frequently 

 dissolve out the pigment entirely. Many of the species of these 

 genera, too, readily bleach to white. I have naturally bleached speci- 

 mens of many species and artificially bleached ones are frequently 

 met with. 



Having noticed the development of yellows, reds and browns, and 

 the repeated instances in which insects normally of one of these 

 colorations develop varieties of the allied colours, we may now trace 



