72 THE MOTHS OF THE BRITISH ISLES. 



The Silver Y {Plusia gamma). 



This species, represented by portraits of two specimens on 

 Plate 26, Figs, i and 2, varies somewhat in the ground colour 

 of the fore wings, which ranges from a whitish grey through 

 various tints of grey and brown to velvety black. The melanic 

 form last referred to is very rare, but I caught one example of 

 it at Eastbourne in the late summer of 1888, and I saw, but did 

 not secure, another near Esher in the autumn of 1906; one 

 taken at Dartmoor in September, 1894, is in Mr. F. J. Hanbury's 

 collection. 



Occasionally a purplish red tinge, often present below the 

 silvery Y, spreads over a larger area of the fore wings. The 

 Y-mark is well defined as a rule, but now and then specimens 

 are found in which only the tail of the Y is distinct. 



The caterpillar varies in general colour from pale green to a 

 dark olive green approaching black. In the white dotted paler 

 green forms there are several transverse whitish lines, some of 

 them wavy, between the yellowish spiracular line and the dark 

 green line along the middle of the back ; head, marked with 

 black on each cheek. It will eat almost every kind of low- 

 growing vegetation, either wild or cultivated, and in some years 

 may be found throughout the summer. Small larvae were 

 recorded as seen at the end of October, 1901. The blackish 

 chrysalis is enclosed in a whitish cocoon, often placed under 

 leaves of thistle, burdock, etc. 



The moth is seen in the spring and early summer (most 

 probably immigrants), and again in the autumn, when it is 

 generally more abundant. 



This well-known migrating species has been observed in 

 greater or lesser numbers over the whole of the British Isles. 

 Its distribution abroad embraces the Palaearctic Region, North 

 Africa, and North America. 



