PIERINM. 
165 
Western Himalayas. There it flew very strongly and fast, now under the Horse- 
Chestnut trees, now in the sunlight over the rooky bed of the stream. I caught one 
or two in June, resting or fluttering over the margins of the stream ” (MS. Notes, 
1864). <e There seems to be two forms of Sanaca, one dark, answering to your 
description, from Masuri, the other almost white, from Kunawur” (id. Epist. Nov. 
18th, 1869). In a subsequent letter, to the late Mr. W. S. Atkinson, dated 
Nov. 18th, 1874, Col. Lang writes: Sanaca is an early summer insect, and I 
think local. At my house in Masuri, in May, 1868, I could always see half a dozen 
in the air, always at a great height, looking like Swifts or Swallows, until your eye 
was focused and recognized their size and distance; rarely coming within reach of 
the longest net, and never settling unless on tree-tops. This species varies in depth 
and breadth of black markings, and, like all the Thycos , it is scented like Jargonelle 
pears.” Mr. L. de Niceville (Trans. Ent. Soc. Loud. 1889, p. 843) says “ through 
the kindness of Mr. P. W. Mackinnon I have received fourteen males and five 
females of D. flavalba and Sarnica from Masuri, and have also before me six males 
of these two species, also from Masuri, and five males and one female flavalba (which 
constitute the type specimens of that species) from Kunawur, contained in Col. 
Lang’s Collection, captured by himself many years ago. As regards these latter 
specimens, Col. Lang in discriminating them and Major Marshall in describing them 
as distinct species, were quite justified, though both the Masuri and Kunawur 
groups of specimens are very variable in the amount of black markings they exhibit, 
on both surfaces, there is no connecting link between them. My fresh specimens 
from Masuri supply this link. When arranged in a graduated series from the 
lightest marked specimen to the darkest, at no point can you draw the line dividing 
them into two species. Mr. Mackinnon writes me: 4 I am sure the dark and light 
coloured ones belong to the same species, as I got dozens of all shades in one place, 
and in one forenoon. They were all chasing each other, at times six or seven 
together. Mine were all caught in open places in forests of Mouroo Oak (Quercns 
clilatata) at Nag Tiba, near Masuri, 5,000 feet altitude, in the latter half of May and 
beginning of June, and at Tehri Gurhwal, near Masuri, 8,500 feet, in June. I have 
seen them often in Masuri, but captured them very seldom.’ I should remark of 
the female from Masuri that none of them are as light coloured as the palest male 
flavala ; in fact, they vary too, but not so much as the male, the lightest specimens 
equal flavalba, the darkest equal Sanaca We possess specimens of both sexes of 
Sanaca from Masuri, taken by the late Capt. T. Hutton. A female from Masuri 
is in the British Museum Collection, and a male of the pale form ( flavalba ) in the 
Hewitson Cabinet. 
Of our illustrations on Plate 528, figs. 1, la, b, are from the Masuri males, and 
lc, d, e, from W. Himalayan females. 
