122 THE "ESSEX EMERALD" MOTH.
Essex some few years before, but had kept the matter secret, gave the
following account of his own independent observations :—
"While collecting micro-larvae on the Essex salt-marshes last week, I took one
larva of the rarity, Geometra smaragdaria, from a plant on which I should never
have thought of looking for the species, and though I had never seen the larva
before, and was not even thinking of it at the time, I knew in a moment what it
was, from its being covered all over with small pieces of leaves and scaly portions
of its food-plants, reminding me of the larva of Phorosdesma bajularia. I cer-
tainly should not have seen it had it not stretched itself out and waved its head to
and fro with a tremulous motion ; for its mimicry of dead portions of its food-
plant is so perfect that it took me some little time to find it after I got home,
although there were only a few small pieces of the plant in the box. It is now
three years since I first went after this larva, and many long and fruitless journeys
I have had since that time, extending over miles of ground in every direction on
the salterns. Year after year I was searching the wrong plants ; for although I
worked up the subject as well as possible by all the books that contained any
information about the species, the knowledge I gained was quite useless as
regards its food, so that my journeys always ended in disappointment. They were
not, however, altogether unprofitable, for I have added a great number of very
local species to my collection, from larvae taken in the district, which I certainly
should never have found had it not been Geometra smaragdaria which first
induced me to collect over such a very uninviting and desolate looking locality."
At the meeting of the South London Entomological Society, on
September 17th, 1885, Mr. Elisha exhibited P. smaragdaria "from
larvae taken in the Essex salt marshes."
In the "Entomologist," vol. xix. (1886) p. 211, Mr. H. Jobson, of
Walthamstow, records breeding a "splendid series of P. smaragdaria,
the larva of which I found on the Essex coast last autumn "—and on
the same page Mr. J. A. Cooper, of Leytonstone, says :—"From
larvae I collected on the Essex salt marshes last autumn, I am now
breeding a fine series of P. smaragdaria. The species appears to be
well distributed along the Essex side of the mouth of the Thames."
Mr. Cooper has kindly favoured the editor with the following more
detailed observations under date, January 13th, 1887 :—
" I was pleased to breed a fine series of this beautiful species last season from
larvae: I collected on the salterns on the Essex side of the Thames during the pre-
ceding autumn. The larvae; were found in the months of October and November,
feeding in cases made of their food plant, and they hybernated on dead stems,
etc. The larvae recommenced feeding in early spring, and grew to full size rather
quickly. When full fed they present a very curious appearance as the cases are
then composed of pieces of the food plant, and are a good inch in length. In
confinement I noticed one individual had attached to its case a piece of paper and
a long thread hanging from the muslin cover of the breeding cage. The larvae pu-
pated in a slight web, spun amongst the food plant or any convenient herbage near.
The perfect insect emerges in July, but I was unable to meet with it at large, as
owing to its sluggish habits it is difficult to dislodge from its place of concealment.
One curious and interesting fact in the life history of this species is that some of
the larvae: found must at times have been submerged by the tide, and while walk-
ing along a bank this winter, from which I had collected larvae, I noticed the line
of drift left by the last tide was considerably above where the food plant grew."