The male of this species (Plate VII, fig. 1) is readily to be distinguished from all other members of the genus by its pale glossy blue, but the female (fig. 2 of Plate VII) so closely resembles that of _Bellargus_ that it is often a somewhat difficult matter to discriminate between them. The following, however, are a few points worthy of observation: The upper side of the female _Corydon_ has the bases of the wings more or less sprinkled with the pale silky blue that characterises the male; and the black bars of the fringe are _usually_ broader in _Corydon_ than in _Bellargus_. The black-centred spots of the under side are also usually more conspicuous in the former species than in the latter. [Illustration: FIG. 91.--THE CHALK HILL BLUE--UNDER SIDE.] The difficulty of identification is increased by the fact that both these butterflies frequent similar localities, and are often on the wing at the same time; but although _Corydon_ is certainly a frequenter of chalky districts, yet it is often found plentifully in districts far removed from the chalk, notably at Arnside in Lancashire, and in Epping Forest. The butterfly is out in June and July. The caterpillar is green, with two rows of short yellow streaks on the back, and a yellow stripe on each side. It feeds on the purple and Dutch clovers (_Trifolium pratense_ and _T. repens_), bird's-foot trefoil (_Lotus corniculatus_), horse-shoe vetch (_Hippocrepis comosa_), and lady's fingers (_Anthyllis vulneraria_). _The Holly Blue_ (_Lycaena Argiolus_) While all the other Blues delight to sport on low flowery banks in the full blaze of the summer's sun, the Holly Blue prefers to flit among the branches of trees, often many feet from the ground. The larva feeds on the flowers of the holly (_Ilex Aquifolium_) in the spring, and on those of the ivy (_Hedera Helix_) late in the summer; also on the alder buckthorn (_Rhamnus Frangula_); and it is in localities where these grow that we may find this lovely Blue sporting among the branches, or resting on a leaf with its wings folded together, thus making itself conspicuous among the dark foliage by exposing the pale silvery blue of its under surface. The upper sides of both the male and female are shown on Plate VII (figs. 3 and 4 respectively), where the beautiful lilac blue will be seen to have a border of black, wider in the latter than in the former. [Illustration: FIG. 92.--THE HOLLY BLUE--UNDER SIDE.] The under surface is spotted with black, as shown in fig. 92, and has no border of orange spots. This is a double-brooded butterfly, appearing first in April and May, and then again in August. It is not at all uncommon in the south of England, and extends northward as far as the Lake District, but is not found in Scotland. It is generally distributed throughout Ireland. The caterpillar may be looked for in June and October. It is light green, with a line of dark green down the back. _The Mazarine Blue_ (_Lycaena Semiargus_)