The British history of the grey tinged pale golden species, shown on Plate 22, Fig. 4, dates back only to 1890. In that year, on July 2, Mr. Christy, of Watergate, Emsworth, found a specimen in his illuminated moth trap; this was noted in the Entomologist for August, 1890. From subsequent records it appears that a specimen had been taken on the same date at a gas lamp near Reading, by Mr. W. Holland; whilst one was captured, at a light, near Tunbridge Wells on July 1. The earliest British specimen, however, was one netted whilst hovering over flowers of Delphinium at Dover, on June 25 of the same year, but this was not announced until October. Since its arrival here the species seems to have spread over England at a great rate, and it has recently been reported from Cheshire. In some southern gardens the caterpillars abound to such an extent that they are regarded as a plague. On the continent it is said to feed on sunflower, artichoke, burdock, and cucumber.
The caterpillar is green, dotted with white; a dark line along the back and a white one along the sides. In the early stage it is black or sooty brown, and hides itself among the spun together flower buds, or in a turned down tender leaf. It feeds in May and June, occasionally found in late April, after hibernation, and a second generation sometimes occurs in July and August. Monkshood (Aconitum) and larkspur (Delphinium) are the usual food plants, and it is curious to note that whilst some observers state that larkspur alone is eaten, others say that monkshood is the only food. The moth flies in June and July, and sometimes there is an emergence in August and September. It visits the blossoms of various garden plants, and is also attracted by light.
The caterpillar, represented on Plate 27, Fig. 1, was found with others on larkspur in Mr. Herbert Smith's garden at Wallington, Surrey. The cocoon and chrysalis is from a photo by Mr. H. Main. Another photo by Mr. Main shows the young caterpillar constructing its retreat.
According to Duponchel this species occurred in Normandy, Central and Northern Europe, as far back as 1829. A much paler form inclining to silvery, var. esmeralda, Oberthür, is found in Ussuri, North China, and other parts of East Asia.
Two forms of this metallic-looking species are represented (Plate 22); 5 is typical and 6 shows the ab. juncta, Tutt. Between these are various intermediate stages leading to the complete division of the central band. The broken central band is a character of var. nadeja, Oberthür, from Amurland and Japan, but that form has also a more or less complete series of ochreous-brown dots on the outer area. The metallic colour is sometimes greenish in all forms.
The caterpillar is pale green, with a darker green line along the middle of the back, bordered on each side by an irregular white line; an oblique white streak on the sides of each ring from 4-11; a stripe low down along the sides is white; head, yellowish tinged. It feeds on stinging nettle, probably on other plants, and after hibernation attains full growth about May. In favourable seasons caterpillars also occur in July and August. The moth is out in June, July, and August, less frequently in September, and may be found flying along the sides of hedges and ditches, especially where flowering weeds are plentiful, throughout the British Isles; so far, however, it has not been recorded from the Hebrides, Orkneys, or Shetlands.
The more or less square golden (sometimes green-tinged) patch on the velvety purplish brown fore wings, distinguish this species (Plate 24, Fig. 1) from any other British Plusia.
The caterpillar is green, with a darker line along the middle of the back, and a fine white line on each side of it; there is a dark green stripe low down along the sides, edged below with white, and oblique white lines run from it to the central line on rings 3-11. It feeds on hemp-agrimony (Eupatorium cannabinum), hibernates when small, and completes its growth in May or early June.
The moth is out in July and August, and is said to be occasionally seen, on sunny days, flying about, or resting on, the flowers of the hemp-agrimony and other plants. Night, however, is its more usual time of activity, and it may also be found at the blossoms of the larval food plant, and at those of honeysuckle, etc.