VISUAL POWERS OF THE BUTTERFLY. 155 



the quay of Belfast ; but as a crowded wharf is a 

 place but iU adapted for racing after butterflies, I 

 had to allow the unusual visitant to escape, but not 

 until I had been several times so near, as to preclude 

 the possibility of any mistake as to the insect. I 

 have taken it in the neighbourhood of Portarlington, 

 in the Queen's County, where it is always considered 

 extremely rare. In the Spirehill wood, near to the 

 same town, I have met in great abundance one of 

 the most beautiful native butterflies, the silver-streak 

 {Argynnis Paphia). It appeared, in quantity, to be 

 almost equal to the pretty little brimstone moth 

 {Rumia cratcegata), which flies in the dusk of 

 evening under the hawthorn hedges. I have never 

 seen any species of butterfly in the same profusion, 

 not even the common white. Yet, in the immediate 

 vicinity of Belfast, this insect is never seen. The 

 only parts of the north of Ireland in which I am 

 aware of its existence, are Tullamore Park, county 

 Down, and Shane's Castle Park, county Antrim. 

 An instance of the visual powers of this insect fell 

 under my observation. Being in the Spirehill wood 

 with two young friends, each armed with a butterfly 

 net, the boys were enjoying, with great glee, the 

 sport which the place aflforded. One of them, in 

 the excitement of the moment, made "one fell 

 swoop" with the net at one of the Paphian butter- 



