Lepidoptera The Pale Clouded Yellow Butterfly – Colias Hyale
The ground colour of this butterfly (Plate II, fig. 2) is very variable. It is usually a sulphury yellow, and on this account the insect is commonly known as the Clouded Brimstone; but sometimes the yellow is exceedingly pale-almost white-and tinged with green.
A very large black blotch, broken by indefinite patches of the ground colour, fills up the tip of each fore wing, and extends to the anal angle, becoming narrower as it approaches this point. A black oval spot lies just above the middle of this wing.
The hind wings are bordered with black, and a conspicuous spot of deep yellow lies very near the centre of each.
The antenna are rather short, compared with those of the preceding members of this family, and are distinguished by their reddish-brown colour.
The male and female of this species are similarly marked, but the ground colour of the latter is commonly paler.
This is not by any means a very common butterfly with us, though it is very plentiful on the other side of the Channel; but it has a way of taking us by surprise in certain seasons, and then almost neglecting us for several years together.
Its head quarters are certainly the coasts of Kent and Sussex, but it has been taken in considerable numbers as far west as Cornwall, and also to a less extent in some of the midland and northern counties. It is particularly fond of lucerne and clover fields, especially those that are situated close to the sea cliffs; and often it may be seen flying over the beach, sometimes even flitting over the breakers away from land till at last it disappears in the distance. This maritime tendency of Hyale makes it probable that a large number of those that are seen on our south-east coasts have made a passage across the narrow end of the Channel.
The eggs are laid in spring, by females that have hybernated throughout the winter, on various leguminous plants, including the lucerne (Medicago sativa), black medick (M. lupulina), purple and Dutch clovers (Trifolium pratense and T. repens), and the bird’s-foot trefoil (Lotus corniculatus), and on these plants you may search for the larva, though it can scarcely be said that you are likely to find it.
The caterpillar is green, with black dots, and a yellowish stripe on each side. When fully grown it ascends a stem of its food plant and changes to a green chrysalis with yellow stripes.
Hyale is single-brooded in England, although two broods regularly appear on the Continent. In our country the perfect insects emerge during July and August. Many of these die before the approach of winter; but, as we have already observed, some hybernate and deposit their eggs in the following spring.