THE PRESIDENTIAL ADDRESS. 9
Entomologist for the year 1885,17 "These [locust] migrations were
not always performed for the purpose of obtaining food, as I have
frequently seen the locusts start out of poplar trees that as yet had
not been much injured by them, of the leaves of which they are very
fond. I have also seen them fly out of wheat-fields that had not as
yet been harvested and out of low, waste places that were covered
with a rank growth of green weeds."
The insects referred to above are, I believe, all habitual migrants,
subject to some fixed law similar to, if not identical with, that gov-
erning birds; and insect migration is probably far more general than
we suppose. The British Association Committee Migration Reports
confirm this.18
Involuntary migration is common amongst birds, and is a subject
quite apart from the periodical and voluntary migrations we are dis-
cussing. As with some insects, this may sometimes be a matter of
necessity caused through overcrowding or the scarcity or failure
of suitable food. The exceptional or more or less accidental pre-
sence of continental or even American species in our islands is not
our theme; certain local storms or disturbances, or other abnormal
weather phenomena may explain the presence of these stragglers.
Doubtless the remarkable irruption of that child of the desert,
Pallas' Sand-grouse, which overran Europe in 1863, and again in
1888, comes within this category, as did that of the Grey Phalarope
in the autumn of 1866. The Waxwing, Crossbill, Quail, Nutcracker,
and many other birds seem very uncertain wanderers to this country.
See a very interesting paper "On some Abnormal Migrations of
Birds," giving full notes from 1863 to 1875, by Mr. John Cordeaux.19
Many North American birds have reached Britain, and it is remark-
able that the greatest number of these have been obtained in Suffolk
and Norfolk. Essex records have been hitherto unavailable.
17 P. 86 or p. 292 of Agricultural Reports.
18 Mr. Gatke sends the following notes of an extraordinary migration of the "Silver Y Moth,"
Plusia gamma, across Heligoland in August, 1882 :—"On Aug. 13th, at 1 a.m. till 4, thousands
on thousands passed the Heligoland Lighthouse, travelling E. to W. From 11 p.m. on the 15th,
till 3 a.m. on the 16th, millions, like a snow-storm, all belonging to the same species, passed for-
ward in the same direction. Again, on the 18th, from 11 p.m., till 3 a.m. on the 19th, thousands
on thousands were observed under the same circumstances. Some scores caught for identifica-
tion were all in most perfect plumage ; no fading or abrasion (4th Report, p. 47). At Heligoland
on the night from Aug. 6th to 7th, S.E., a considerable flight of the 'Silver Gamma Moth,'
Plusia gamma, but nothing to be compared with the perfect snow-storms of this moth which
passed in the autumn of 1882, all going west. On Oct. nth, S.S.W., there was a considerable
flight oi Hybernia defoliaria, the 'Mottled Umber Moth,' mixed with Hybernia aurantiaria,
the 'Scarce Umber' ; and also during the nights of the last week in October repeated flights of
these moths." With reference to the great flight of Plusia gamma in 1882, a notice of which
appeared in our last Report, 1882, p. 47, Mr. Charles Williams, of the Hanois L.H., Guernsey,
sends this note :—"Seeing Mr. Gatke's remarks in your Report about the Gamma Moth, I beg
to say that they were here in June or July" (5th Report, p. 58). See 6tb Report, pp. 67-8 ; 7th
Report, p. 54 ; 8th Report, pp. 47-8, etc.
19 "Field," March nth and 18th, 1876.