TRIFID/E. 281 



varies in depth of colour in conformity with the fore wings, 

 and the hind wings in both sexes follow suit — from clear, 

 pure white in the palest males to pale greyish brown in the 

 darkest ; and in the females from pale grey, varied with 

 white, to dark grey. Occasionally, in both sexes, the fore 

 wings are tinged with grey rather than brown. There is also 

 a tendency to local variation, a peculiar faint shade of um- 

 breous, for instance, in Lancashire specimens, differing a little 

 from the various shades observable on other coasts, while in 

 the south-west are seen rather brighter shades of reddish. 

 All the variations melt insensibly into each other; it appears 

 impossible to draw any definite lines of variation ; yet the 

 species has been loaded with varietal or synonymic names — 

 sagittifcrus, trigoncdis, davis, clavifcra, and others — which 

 seem to have no definite application and to be of little im- 

 portance. 



On the wing in July and August ; in very early seasons, 

 and warm districts, occasionally before the end of June, but 

 apparently in but a single generation. 



Larva smooth, shining, naked, moderately plump, two 

 inches in length, pale olive-grey, rather tinged with brownish 

 or purplish on the back ; head yellowish brown ; dorsal plate 

 brownish, barred with blackish brown or purplish brown ; 

 dorsal and subdorsal lines darker grey or purplish grey, 

 double, rather obscure ; ordinary raised spots and spiracles 

 black ; under surface very pale grey. 



August to May, apparently dormant only in very cold 

 weather, feeding during the milder portions of the winter ; 

 on grasses, various species of Galium, Alsine, and other low 

 plants growing on sand hills ; hiding itself in the daytime 

 at a depth of one or two inches beneath the surface of the 

 sand, but coming out at night to feed. Will eat lettuce and 

 dandelion. 



Pupa pale reddish brown, beneath the surface of the sand. 



