330
THE ESSEX NATURALIST
of the large number of larvae to various friends, and some of the moths
were of a form never previously recorded from Britain but known from
parts of France. It therefore appears, as previously suspected, that the east
coast occulta are temporary colonists from abroad which are unable to make
a permanent home here and die out in year or so. This is the more curious
as we have a smaller, darker, native race in the highlands of Scotland which
extends its range to the Orkneys.
It must be remembered that many species demand certain conditions to
flourish, a curious example of which is the Brown-tail moth (Euproctis
chrysorrhoea). In 1900 it was extinct in Kent, and after being extinct in
Essex had just reappeared at Colchester and Harwich. The famous J. W.
Tutt, editor of The Entomologist's Record, appealed to collectors to be
sparing in their captures to give it a chance to establish itself. It is not
necessary for any detailed description to be given of how it besieged Canvey
just after the last war, but my friend Mr. D. J. Legg, the Senior Sanitary
Inspector there, does not exactly echo Tutt's sentiments towards the Brown-
tail. It is, of course, now known from records from lightships that both
the Brown-tail and the Satin are periodic immigrants.
Amongst occasional immigrants since Harwood wrote are the Black V
(Leucania V-nigrum), the Purple Cloud (Cloantha polyodon), the Scarbank
Gem (Plusia limbirena), the lovely Golden Crescent (Plusia confusa), the
Sussex Emerald (Thalera fimbrialis), the Lettered China-mark (Diasemia
litterata), and the Splendid Knot-horn (Dioryctria splendidella), of all of
which specimens have been taken by Mr. Dewick at Bradwell-on-Sea;
and the Isle of Wight Knot-horn (Heterographis oblitella), of which three
of the seven known British specimens have occurred in the past three years
in my garden at Westcliff.
Apart from the mercury vapour light, however, a good deal has been
discovered about the Essex micro-lepidoptera. New insects to the county
which I have discovered have been the Reed-mace Grass-veneer (Crambus
paludellus), the Scarce Water-veneer (Donacaula mucronellus) and, as far
as rural Essex is concerned, the lovely Rose Plume (Euenaemidophorus
rhododactyla) which had hitherto only been recorded from the Brentwood
area. Perhaps I might also mention the tortrix, Eucosma rubescana, which
I discovered in Kent before I came to live in Essex and which Mr. I. R. P.
Heslop named "Huggins's Bell". Almost directly after coming to live in
Essex in 1932, I found this on the sea-wall near Wakering.
The feature today amongst resident Lepidoptera is that of melanism, the
causes of which, to my mind, are most imperfectly known. Not only in
a pure atmosphere like that of Westcliff is the Peppered moth (Biston
betularia) going almost entirely black, but even on the wildest and most
desolate salt-marshes the formerly pale-drab Dog's Tooth (Hadena suasa)
has now changed to dark brown or blackish in over 80 per cent of captures,
forms unknown in Essex in my youth. The subject of melanism is, how-
ever, too vast and controversial to be dealt with here.
In closing this brief review, I am aware of having given only the veriest
sketch of the subject, lest any attempt at a full treatment would have had
an effect like that of Dr. Skinner's work on St. Jude, which was so
•exhaustive it exhausted all those who had anything to do with it.