THE MACRO-LEPIDOPTERA OF THE SHETLAND ISLES. 251 
_ ground colour yellowish, with darker rufous markings. Most of 
the males have the upper wings more or less spotted with brown 
and brownish red, and out of the whole number I found but two 
of the usual silvery colour of the type both on the upper 
under wings and thorax. 
The range of variation in the females is not nearly so great, 
and the plate shows the most conspicuous aberrations; these are 
chiefly in the prevailing ground colour of the upper wings, 
which varies from brown to yellowish buff, and in two of those 
figured a very rosy hue pervades the lower wings, particularly in 
the large specimen at the bottom of the plate. I did not find 
one instance among the females where the silvery colour usual in 
the males existed, but some of the very large silvery males, with 
the thorax buff-coloured, might easily have been mistaken for 
females. It will therefore be seen that the variations consisted 
generally in the males being coloured more or less like the 
normal females. The sexes may be readily distinguished by 
the existence, in the males, of a tuft of long hair-like scales on 
the hind legs. 
It is possible that in the Shetlands an archaic coloration of 
Hepialus humuli is preserved in those specimens where the 
sexes are alike and resemble the normal southern female in 
colour, and that the varieties exhibit the changes which the 
species is passing through towards a perfect differentiation of 
sexual coloration; this view is strengthened by the fact that 
the females are coloured to a great extent like the southern type 
of the species. 
It has also been observed in England that when the males are 
flying in the well-known vibratory manner, the females fly 
towards and against them ; in the Shetlands, where in summer 
the nights are so much lighter than with us, it is not so necessary 
that the males should be conspicuously coloured to enable the 
females to distinguish them. An examination of the plate 
shows at a glance how much darker the males are in the Shet- 
lands than in England,—one indeed is quite melanic; on the 
other hand, the females are rarely darker than in the type of the 
species. 
(To be continued; with Plate of other species.) 
