45 



geological environment, I know of no better example than that of 

 Criiophos obscuraria. This insect on the chalk downs near Lewes 

 is found almost white with dark markintrs, and of a light gray 

 ground color, Avith darker markings ; but on the peaty soil of 

 the New Forest I have taken it in plenty of a very dark gray 

 color, in some instances nearly black. Specimens obtained in 

 limestone districts are of a browmish gray color. 



Atavism. — In this class I place all variations which show 

 a tendency to reversion to what I conceive to be a common 

 ancestor. Of this I have a few illustrations in my cabinet, 

 and singularly in that usually remarkably invariable species 

 Vanessa lo. Several of the Vanessidae have a row of blue spots 

 on the margin of the wings, these are well seen in Vanessa 

 urficce, V. poIychJoros, V. Antio2)a, and several foreign species. 

 In V. lo. the blue marginal spots appear to be concentrated in 

 the under wings into two large circular patches; but by careful 

 examination of specimens, taken by myself in the New Forest, I 

 find some have on the lower wings small blue spots in the dark color 

 beyond these patches which, to my mind, are evidently traces of 

 the row of blue spots which in Vanessa lo. have become ditferently 

 arranged. In the Larentidae, a family commonly known as carpet 

 moths, the bulk of the species have a well-defined broad central 

 bar; but this is more or less broken in some species, yet amongst 

 them it is not unusual to find one with the central bar well 

 defined. This I take to be a case of reversion to the markings of 

 a common ancestor. Cidaria corylata in the normal form has 

 the bar interrupted; but I have a specimen in which it is as 

 complete as is typical of the genus. In Melanippe hastata the bar 

 is usually interrupted, but I have one in which the bar is com- 

 plete. Melantkia rubigaiafa has usually only the commencement 

 of the bar at the costal edge of the wings, but frequently traces 

 of the obliterated bar are found on the inner edges of the wings. 



Dimorphism. — In this class I place all those insects which 

 have two well defined types of color, generally without inter- 

 mediate variations being found. The best type of this class found 

 in the British Isles is Argynnis pajyhia and its dimorphic female 

 form VaUzina. In this case the normal coloration has red for 

 the ground color of all the wings, but in Valezina the ground 

 color is green. Although I have spent many days in the New 



