The males vary a little in the width of the marginal border, and in some females there is almost as much fulvous on the discal area of the wings as in the male; in the darkest females the spots always appear paler than in fulvous specimens. On the under side the ground colour is sometimes olive-brown rather than green.
The following account of the life-history of this butterfly is adapted from Mr. Frohawk's article on the subject published in the Entomologist for 1901:—
In August, whilst watching some of the butterflies on the wing over a patch of chalky ground covered with a short dense growth of various grasses, etc., he noted a female hovering close over the plants. Presently it settled on a tuft of hair grass (Aira cæspitosa), and after walking over and among it a little time, she curved her abdomen down, and deposited a single egg on one of the fine hair-like blades, or, rather, spines, and close by, within an inch, another egg was found. Afterwards some plants of this grass were potted up, and some females placed on them. These deposited a large number of eggs upon the grass-stems and blades.
The egg when newly laid is pearl white with the slightest yellowish-green tinge, which very gradually turns deeper in colour, assuming a pale straw-yellow on the sixth day, and so it remains until January, when it becomes paler.
The caterpillar hatches out at the end of March or early in April. It does not eat the empty egg-shell, but directly after leaving the egg it starts spinning the fine grass together into a somewhat dense cluster an inch or two above the ground. In this compact shelter the larva lives and feeds upon the grass surrounding it, remaining almost always completely hidden. Sometimes as many as three or four live together. When full grown and about one hundred days old, the caterpillar is of a dull olive-green colour, with a black collar on the first ring, and the entire surface densely sprinkled with minute shining black warts, each emitting a tiny amber-coloured spine with a cleft knobbed apex. The head is blackish marked with ochreous lines. It still resides in a tube of grass spun closely together, and feeds on any other kind of grass that happens to be interwoven with the Aira. Just before pupation the caterpillar often crawls restlessly about, but in some instances it does not leave its place of feeding, and spins a strong, coarse network cocoon among the grass close to the ground, weaving the gnawed loose pieces of grass with the fine stems and blades, and therein pupates during the latter part of July.
Larger Image
Pl. 126.
Large Skipper. 1, 3, male; 2, 4 female.