208 THE MOTHS OF THE BRITISH ISLES. 



Grass Rivulet {Perizoma alhilatd). 



Although some English specimens approach the larger and 

 whiter typical form, the species as it occurs in the British 

 Isles is generally greyer, var. griseata, Staudinger ; two 

 examples of this form are shown on Plate 83, Figs. 10 and 11. 

 In the Shetland Isles, the species assumes a darker coloration, 

 and is either well marked on the fore wings, as in Fig. 14, or 

 almost plain, as in Fig. 13 (ab. thules^ Weir), which is an 

 extreme aberration of the form subfasciaria^ Boheman. In other 

 examples of a deep leaden grey, or brown tint, the central 

 area is no darker than the rest of the wing. In the Isle of 

 Lewis a white form with faint markings is prevalent, and this 

 leads up to a clear white aberration devoid of markings, ab. 

 niveata, Stephens, = hebudiufn, Weir. 



The wrinkled caterpillar, which feeds, in July and August, on 

 the seeds of the yellow rattle {Rhmatithics crista-galli), and 

 lives in the capsule, is whitish, inclining to greenish, dotted with 

 black, and striped with dark green on the back and sides ; 

 head, black and glossy ; plates and first and last rings of the 

 body dusky. (Plate 84, Fig. i.) 



The moth is out in May and June, sometimes later. It 

 occurs chiefly in dry meadows where the yellow rattle flourishes, 

 and is to be seen on the wing, often in large numbers, in the 

 late afternoon about sundown. Generally abundant in suitable 

 places, throughout the British Isles. 



The Barred Rivulet {Perizoma bifasciaia). 



Haworth described two forms of this species, and a specimen 

 of each is shown on our Plate 83. Fig. 4 represents bifasciata 

 {bi/aciata^ the Double-barred Rivulet), and Fig. 5 depicts 



