330 
PIERIDAE 
reaching the coast it wanders over the country and resorts 
to Clover and Lucerne fields, and rough, uncultivated 
ground generally where Clover and other flowering plants 
abound. 
In certain years the Clouded Yellow occurs in abundance 
throughout the southern counties of England and extends 
its range to all parts of the British Isles, but occurs in fewer 
numbers northwards. Abroad it ranges over the southern 
half of Europe, northern Africa, western Asia, and Persia. 
Since the beginning of last century it occurred commonly in 
the years: 1804, 1826, 1829, 1845, 1857, 1859, 1875, 1892, 
1895, 1900, 1901, 1913, 1928. and 1933. It appeared in the 
greatest abundance in 1835, 1842, 1856, 1865, 1868, and in 
1877 * n the greatest profusion, when its range extended from 
the Orkney Islands to Land’s End, Scilly Isles, and Ireland. 
But in the following year, 1878, there was almost a complete 
absence of this butterfly in Britain ; in the middle of December 
of that year (1878), however, a specimen was found alive in 
Kent. 
For the following very interesting particulars regarding a 
probably unique observation on the migration of this butterfly, 
I am indebted to the Rev. D. Percy Harrison. He states 
in his letter dated December 13th, 1933 : " My greatest 
experience was in Cornwall as far back as 1868, when I was 
only 11, and sat on a cliff near Marazion,. and saw a 
yellow patch out at sea, which as it came nearer showed 
itself to be composed of thousands of Clouded Yellows, 
which approached flying close over the water, and rising 
and falling over every wave till they reached the cliffs, 
when I was surrounded by clouds of C. (=croceus) edusa, 
which settled on every flower. I have some of them still, 
including two helice. Whence they came I know not ; the 
nearest coast of France would be Cherbourg. They swarmed 
in the district for a space of some three weeks and were good 
specimens when they arrived.” 
The irregular appearance of these butterflies, like that of 
C. hyale , puzzled the older entomologists, who were unac¬ 
quainted with the migration of insects. 
Time of Appearance. The early immigrants arriving in 
May and June lay their eggs, which hatch in about six or seven 
