114 NEW ZEALAND MACBO-LEPIDOPTEPA. 



EEEBIA PLUTO, Fereday. 



(Ercbia pluto, Fereday. Erebia mcnila, Hewitson, Ent. Mo. Mag. xii. 10 (1871). Orcina othello, 

 Fereday, Trans. N. Z. Inst. viii. 302, 301, pi. ix. (1876). Percnodaimon pluto, Butl., Ent. Mo. Mag. 

 xii. 153 (1876) ; Catalogue of N. Z. Butterflies, 10.) 



(Plate XL, fig. 8 J, 9 5, 10 under side.) 



This fine butterfly has occurred plentifully on many mountain-tops in the South 

 Island, from Nelson to Lake Wakatipu. It has never been observed in the North 

 Island. 



Tin 1 expansion of the wings of the male is If inches, of the female 2 inches. On the 

 upper side all the wings are a very rich bronzy -black. The fore-wings hare a paler patch near 

 the apex, containing tin, small, and three large black ocelli with white centres; these ocelli are 

 usually joined together. On the under side all the wings are considerably paler and greyer. 

 The hind-wings have a series of pale spots near the termen, and a paler shade across the 

 middle. 



The insect varies chiefly in the number of ocelli. On the upper side of the 

 fore-wings there are sometimes only four, the minute ocellus on the costa being 

 absent, whilst occasionally a small extra ocellus appears below the normal series. 

 On the under side this last-mentioned ocellus is very frequently, but not invariably, 

 present. In some female specimens an extremely minute ocellus may be detected 

 on the upper surface of the hind-wings near the termen. On the under side of the 

 hind-wings in both sexes the series of pale terminal spots are often absent, and the 

 general depth of the colouring varies considerably. 



Mr. Fereday has described and figured a very interesting variation occurring in 

 the structure of the costal veins of this species,* vein 11 of the fore-wings sometimes 

 running into 12 (see Plate I., fig. 26), and sometimes being entirely absent (fig. 25). 

 After reading Mr. Fereday's article I examined the specimens in my own collection, and 

 found that all those taken on Mount Arthur and on Mount Peel, in the Nelson district, 

 had veins 11 and 12 joined, whilst the two specimens I took on Mount Enys, 

 Castle Hill, West Coast Road, had vein 11 absent. As, however, Mr. Fereday has 

 specimens exhibiting both forms of neuration, from Castle Hill and from Mount 

 Hutt, I do not think it likely that the peculiarity is confined to butterflies from 

 any particular locality. Like Mr. Fereday, I have observed that the specimens 

 having veins 11 and 12 joined, are smaller than those having vein 11 absent. 



The perfect insect appears in January, February and March. It frequents 

 shingle slopes on mountains, at elevations ranging from 4,000 to 6,000 feet above 

 the sea-level. Sometimes the butterflies occur in considerable numbers, flying in a 

 lazy, aimless manner in the scorching sunshine, but instantly retreating into crevices 

 between the stones when the sun is obscured. I have observed that this species is 

 most abundant in the neighbourhood of the carpet grass, on which I fully anticipate 

 its larva feeds. It seldom, however, settles on this grass, preferring to alight on the 

 shingle, which, owing to the rarefied air existing at such high elevations, soon 

 becomes intensely heated by the sun's rays. 



When disturbed this insect flies with considerable rapidity and thus often eludes 

 the net, so that the capture of a good series of specimens on a rugged mountain- 

 top is usually very exciting, if not actually dangerous work. As with many other 



* -Trans. N. Z. Inst.' xv. 197. 



