68 MR. W. YARRELL ON THE ECONOMY OF 
and the extent of the injury it inflicts, isin the ‘Transactions of the Royal Society’ 
for 1783: in which William Marshall, Esq., an agriculturist in Norfolk, details at some 
length the particulars of the appearance of the parent fly during 1782, the year in 
which he wrote his account; and refers to a previous visitation, about twenty-two 
years before that time, when the loss from the destruction of the turnip crop was but 
little less severe. 
In the year 1782, Mr. Marshall informs us, many thousands of acres upon which a fairer 
prospect for a crop of turnips had not been seen for many previous years, were ploughed 
up; and as the season was too far advanced to expect any profit from a fresh sowing, 
the loss to the farmer individually was considerable, and to the county immense. 
‘« Tt was observed,” says Mr. Marshall, ‘‘in the canker year above mentioned, that 
prior to the appearance of the caterpillars great numbers of yellow flies were seen busy 
among the turnip plants, and it was then suspected that the canker was the caterpillar 
state of the yellow-fly ; since that time it has been remarked, that cankers have regu- 
larly followed the appearance of these flies. From their more frequently appearing on 
the sea-coast, and from the vast quantities which have, I believe, at different times, 
been observed on the beach washed up by the tide, it has been a received opinion 
among the farmers, that they are not natives of this country but come across the 
ocean ; and observations this year greatly corroborate the idea. Fishermen upon the 
eastern coast declare that they actually saw them alight in cloud-like flights ; and from 
the testimony of many it seems to be an indisputable fact that they first made their ap- 
pearance on the eastern coast ; and moreover that, on their first being observed, they 
lay upon and near the cliffs so thick and so languid that they might be collected into 
heaps, lying, it is said, in some places two inches thick. From thence they proceeded 
into the country, and even at the distance of three or four miles from the coast they 
were seen in multitudes resembling swarms of bees.” 
Whatever may have been the source from which this country derived the original 
stock, it is quite certain that during the last year the maritime counties on the east and 
south coasts were the most infested ; but the simultaneous appearance of the insect in 
some inland counties also but too clearly proves that it is now established as a native. 
Early in July 1835 the yellow-fly was again seen in abundance upon the young 
turnips, and it was recollected by some that this was the fly which prevailed also in the 
year 1818, and which was followed by the caterpillar which they knew by the name of 
the blacks. Another observer, as noticed in a popular weekly publication, said, ‘‘ It is 
of no use hoeing these turnips, for I perceive this year a fly which is the forerunner of 
the ‘ nigger’ caterpillar.” 
These predictions were soon verified. The female fly, by means of a delicately ser- 
rated instrument under the abdomen, is enabled to make a small aperture on the under 
surface of the leaf of the turnip, in which she deposits a single egg ; and each female 
produces and deposits in different places about twenty of these eggs. In eight or ten 
days the eggs are hatched, and the dark-coloured caterpillars crawl forth and commence 
ma ty 
