The egg when first laid is green in colour, but as the caterpillar matures within the colour changes to greenish-black, with the ten ribs showing up more or less transparent. The egg is laid in an upright position on nettle leaves and young shoots, but not in batches like those of the Tortoiseshell, etc.
The caterpillar varies in colour. Some are blackish freckled with white, with two yellow stripes, sometimes broken up, on the sides; and the rows of branched spines yellow, except those nearest the head, which are black or tipped with black. Others are greyish, or grey marked with yellowish-green. Others, again, are dark brownish, with the spines on the back pale, and those on the sides black; or all the spines may be shining black (Hellins).
The chrysalis is greyish, prettily ornamented with gold along the centre of the back and on the thorax and head. The projections are also tinged with metallic gloss. It is generally suspended under a canopy of nettle leaves.
The caterpillars do not live in companies like those of the Peacock and Tortoiseshells, but each individual constructs for itself a kind of tent (see Plate [48]) by spinning together the leaves of its food-plant, the common stinging-nettle. Although the caterpillar is well concealed in such hiding-places when newly made, it "gives itself away" when it has partly consumed its home. It has been found on pellitory (Parietaria officinalis), and also on hop (Humulus); but I have found that caterpillars fed on hop alone always produce small butterflies.
Pl. 48.
Red Admiral.
Caterpillar's shelter-tent, and chrysalis.