A SURVEY OF ESSEX LEPIDOPTERA 329
a hope that it is returning, and the Grayling (Eumenis semele), which
Harwood thought a great rarity, is common in several places in the north,
notably Bere Common.
The Kent Black-arches (Nola albula) has been taken at light in the
north: this is possibly only a migrant, but where it turns up elsewhere
it usually seems to colonize successfully. Insects, however, which colonize
successfully in the south do not always succeed on our heavy clay. The
Toadflax Brocade (Calophasia lunula) has, since the war, migrated to this
country and has effected large settlements on shingle in Kent and Sussex,
where its curious caterpillar, looking very like the larva of the. Large White
butterfly, can be seen in quantities at the right time of the year on Toad-
flax. In September, 1953. I found three full-fed larva?, one of which I
reared successfuly, near Wakering, and from the condition of the food-
plant a large brood must have been feeding, but in subsequent years no
permanent colony has been found, and Mr. Dewick, who took the moth
at Bradwell-on-Sea, has also since found no colony.
However, Webb's Wainscot (Nonagria sparganii) is now found in several
localities on the coast. I think this is a, migrant established in Essex
which is now spreading, as I recently had a specimen found on a shop
front in Leigh-on-Sea brought to me for identification. This is a place
quite outside its usual range.
It may at this point be interesting to mention that on warm, damp
nights marsh insects, usually supposed to be sedentary, appear to disperse
over the surrounding country. My friend Mr. A. L. Goodson took, a
couple of years ago, a number of Brown-veined Wainscots (Nonagria
dissoluta) at his light traps at Tring (in the town) and Ashridge. This
moth has never been suspected of migration, but both lamps, some miles
apart, attracted several specimens on the same night, and there is no
previous record for the district. The moth is usually considered sluggish
and only to buzz about the reed-beds where it breeds, but at Ashridge
it was up on the high chalk.
I have also made some remarkable captures of marsh and salt-marsh
insects at a light-trap in my garden, two miles from the nearest suitable
habitat. The recent invention of the mercury vapour light-trap seems
likely to revolutionise our ideas of the habits of Lepidoptera. Apart from
the well-known migratory insects, a number seem to make considerable
local movements in suitable weather. Further, continental insects usually
considered sedentary also come over, particularly to the coasts of Kent
and Essex. The Golden-rod Brindle (Lithomoia solidaginis) and Scarce
Silver-Y (Plusia interrogationis) are northern insects in this country only
found on moorlands from Staffordshire northwards. In 1954, however,
a number of the German race of solidaginis came over to the east and
south coasts, specimens occurring at Southend, Hockley and Bradwell, and
in 1955 some of the alpine race of interrogationis arrived, also occurring
at Hockley and Bradwell. It was hoped that these would found colonies,
as although the British solidaginis only feeds on bilberry (what's in a
name?), the German feeds on sallow and a variety of other plants. How-
ever, none occurred in 1955, and I am not expecting any home-bred
interrogationis in 1956.
The Great Brocade (Eurois occulta) has been known sporadically from
Essex for many years, but its exact status has been doubtful. However,
this year I have been able to help in settling this. A good number came
to light here and at Bradwell in circumstances that made it most probable
they were immigrants. I reared a brood from one of these, sending part