The food plant of the caterpillar appears to have been the water dock (Rumex Hydrolapathum), on which the eggs were laid late in the summer. It is probable that the caterpillar was a hybernator, seeking its winter shelter while still very young; and it was full fed in June.
Its colour was green, with a darker stripe of the same colour on the back; and the chrysalis was attached by anal hooks and a cord round the body.
The Small Copper (Polyommatus Phlæas)
The only other British member of the genus Polyommatus—the Small Copper—is one of the commonest of our butterflies. It may be found in nearly all parts of the British Isles from April to September, more particularly in April, June, and August, for it is apparently triple brooded.
This brilliant and lively little insect is shown on [Plate VI] (fig. 9), and, being so very familiar, needs no description.
The caterpillar feeds on different species of dock—the broad-leaved dock (Rumex obtusifolius), the fiddle dock (R. pulcher), the sorrel (R. acetosa), and the sheep sorrel (R. acetosella); also on the ragwort (Senecio Jacobæa). It is full fed about three weeks after hatching, and then changes to a small and stout chrysalis, of a pale brown colour, on the leaf of its food plant.
The caterpillar itself is green, with a reddish line on the back and on each side; and it glides over the surface of the leaves something after the manner of a slug, without exhibiting any very apparent motion of its short legs and claspers.
The Tailed Blue (Lycæna Bætica)
We now come to a genus containing no less than ten species of beautiful little butterflies, known commonly as the 'Blues;' but one of them exhibits no trace of the colour so characteristic of the group, although it resembles the others in structure and habits.