THE "ESSEX EMERALD" MOTH.
123
In the "Proceedings of the South London Entomological Society"
August 19th, 1886, it is noted that Mr. Cooper and Mr. Jobson
exhibited specimens, and figures of the larva at rest and extended are
given. In Lord Walsingham's magnificent collection of the larvae
of Lepidoptera now in the Museum of Natural History at South
Kensington, are four larvae taken in Essex, 11th June, 1884.
In none of the above notes were any descriptions of the larva
given, nor was the food-plant mentioned. For information on these
points entomologists are indebted to Mr. George Elisha, who has
given a very complete "life history" of the moth in the "Trans.
Entomological Society of London" for 1886, p.. 465. The author
found the caterpillars on the Sea-Wormwood (Artemesia maritima,
L.) which is so common a plant on the "saltings," and he has
detected the insect in many places on the Essex coast over an extent
of ground at least thirty miles in length; indeed he is of opinion
that it will be found anywhere along this coast where the sea-worm-
wood grows. The eggs are laid in July on the upper shoots and
leaves of the Artemesia, and, on hatching, the young larvae imme-
diately cover themselves with the cottony down of the plant, so look-
ing like little balls of white wool. Mr. Elisha has kindly permitted
us to extract the following details from his valuable paper :—
" The larvae during the whole of their existence keep the body in an arched
position, except when feeding, when they stretch themselves out a little ; but on
the slightest alarm they again assume the curved position, with the anal claspers
fixed to the plant, and the prolegs drawn up close to their bodies. As the larva
increases in size it increases the length of the morsels of the food-plant it attaches
[by means of some glutinous secretion] to its body which on some adult larvae are
often three-quarters of an inch in length. When the pieces are first attached to
the body they are, of course, green and fresh, but they soon become discoloured,
and in a few days are withered and brown ; then the larvae, in their curved
position, so exactly resemble the dead shoots of their food-plant that they are
extremely difficult to detect, unless some movement betrays them, or one is familiar
with their peculiar appearance. Thus it is evident that the object of the larvae in
attaching these pieces to their bodies is for the purpose of protection against their
numerous enemies.
The larvae continue feeding till about the end of October, by which time they
have attained the length of one-half to three-quarters of an inch, after which they
fix themselves to the food-plant, and remain motionless during the winter months.
With the first warm days of spring, towards the end of February, they begin
moving; and about the first week of March, when Artemesia maritima is again
appearing above the ground, they commence feeding, soon after which they moult
and again cover themselves with pieces of the food-plant, which, being now green
and fresh, give them a healthy appearance. About the middle of June they are
full-grown, when they rest for a day or two, and then spin a loose network cocoon ;
(this they form by drawing together, with silken threads, the pieces of the Artemesia
that are thickly adhering to their bodies, into an oval-shaped covering attached to
the stem of the food-plant), and in it they change to a greyish pupa, with the
striped wing-cases showing very distinctly.
" The larva, when full-fed, is about an inch and a quarter long, of a dirty