COLIAS. 
49 
gradual cooling down took place, so as in time to reduce the 
climate of these regions from a state which may he compared to 
that of the warmer temperate areas of the present earth to a 
condition which culminated in the glacial period, and that during 
this age a special circumpolar fauna was established, some 
survivors of which still inhabit their former abode, having 
gradually regained their ground during post-glacial times. 
Perhaps the above remarks may not he considered out of 
place, whilst we have under consideration the genus Colias, of 
which thirteen species occur in Europe, and out of this number at 
least live are to be found within the Polar Circle. Two species of 
the genus are found in Britain, the “Clouded Yellows,” Colias Edusa 
and G. Hyale. They are both very uncertain in their appearance, 
occurring during some seasons in considerable numbers, after- 
having been scarce or altogether unnoticed for several years 
previously. The year 1877 will always he remembered by British 
entomologists on account of the vast numbers of Colias Edusa that 
appeared throughout the country. 
1. C. Palaeno, Linn. Faun. Suec. p. 272 (1761) ; Syst. Nat. i. 2, 
p. 764; Boisd. Sp. Gen. 2, p. 645. — Europouiene, 
Esp. 42, 1,2; Hub. 434-5. — Philomeiie, Hiib. 602-3, 
740-1. 
Expands from 1-75 to 2-70 in. Wings of the male pale yellow, 
with a black border, dusted over, and sometimes finely veined, 
with pale yellow ; the fore wings have a small black discoidal spot, 
sometimes this is altogether wanting ; the hind wings have a very 
faint and hardly visible pale spot touching the discoidal cell. 
Under side : — Fore wings deeper yellow than above ; the black 
border of the upper side shows through, giving a darker shade to 
the hind margin ; discoidal spot small and nearly annular. Hind 
wings yellow greenish, at the base, with a small pearly discoidal 
spot. The head, antennae and other appendages, as well as the 
prothorax and legs, are red ; the meso- and meta-thoracic segments 
are black, as well as the abdomen, and are covered with white 
downy hairs. The margins of all the wings are fringed with rosy 
H 
