Lepidoptera The Clouded Yellow Butterfly – Colias Edusa
Not only are this and the last species similarly named, but a glance at the figures will show that they much resemble each other in appearance; and we shall also learn presently that in their habits and life history they have much in common.
The male Edusa is shown on 
Plate II (fig. 3), and when we compare it with its relative on the opposite side, we are at once struck with the superior richness of the brilliant orange or saffron of the ground colour. The black border of both fore and hind wings is also denser, wider, and more extensive. The whole of the yellow area of the hind wings is dusted more or less with black scales, with the exception of a round central spot of deep orange, corresponding with the orange spots on the hind wings of Hyale.
Fig. 66.-The Clouded Yellow-Female.
The female, which is shown in the accompanying woodcut, is generally larger than the male, and is further distinguished by the very pale yellow spots that break the black border of both pairs of wings.
Edusa further resembles Hyale in the reddish colour of the antenna; and, in both the species, the red legs form a pleasing contrast with the yellow furry surface of the under side of the thorax.
There is a variety of the female of this butterfly, in which the ground colour is a very pale yellow, almost white. The hind wings are more thickly dusted with black scales than in the normal insect, and the orange spots of these wings show up much more conspicuously from the contrast with their surroundings.
It is usual to apply distinct names to constant varieties of species-names that are to be added to the ordinary title. In this particular case the distinguishing name is Helice, so that we should speak of the variety of Edusa above mentioned as:
Colias Edusa, var. Helice
Like Hyale, Edusa is particularly capricious in its appearance. In certain summers it absolutely swarms in favourite localities, while during the intervals between such remarkable appearances-usually several years-it is positively scarce. The last favoured season was the summer of ’92, during which (from the beginning of August to the end of the summer) dozens might easily have been caught in an hour or two; in fact, so plentiful were they in many places, that they were continuously in sight, often several at one time.
Those in search of this insect should repair to the south coast, especially the south-east, and where lucerne and clover fields are in flower. It has very decided maritime tendencies, and may often be seen flying over the cliffs and beaches, and even skipping over the breakers; but, at the same time, it is more or less plentiful in many inland districts. It has been taken in many parts of Ireland and Scotland, particularly along the southern coasts of these countries; but its head quarters are undoubtedly the southern cliffs of England, from Cornwall to Kent, and also the hilly inland districts of the south-eastern counties.
Edusa catching is very lively sport, and is likely to prove sufficient for any lover of outdoor exercise under a scorching sun; for this butterfly is not only very powerful on the wing, but its flights are usually long, so that a good run is often absolutely necessary in order to capture it. On very hilly ground, such as Edusa loves, chase is often hopeless, and then it is necessary to resort to stratagem. In such a case the best plan is to make a very cautious approach when the insect has been observed to settle, and then secure it with a sudden down-stroke of the net.
The eggs are laid during May and June by a few females that have survived the winter.
The caterpillar may be found in June and July on its food plants, the chief of which are the bird’s-foot trefoil (Lotus corniculatus), and the purple and Dutch clovers (Trifolium pratense and T. repens). Its colour is grass-green, and it is marked with a narrow whitish stripe on each side, which is broken by the yellow of the spiracles.
The chrysalis is of a pale yellowish green, and is marked with yellow stripes and reddish-brown dots.