446 
THE TURNIP-FLY. 
it is immediately attacked by the insect; and, either by devouring 
these leaves, or the heart of the plant which developes the succeeding 
leaf, (or rough leaf,) it is generally destroyed. The smallness of 
the plant, and the extreme delicacy of its hud, leave it peculiarly ex¬ 
posed. It is, however, a general opinion, that after the second series 
of leaves, commonly called the rough leaf, are developed by the plant, 
that the insect will not longer attack it. This latter opinion is, how¬ 
ever, unfounded. The correspondents, almost invariably state, that 
the insect continues its attack, and even commences its attack, though 
the rough leaf has appeared; but, that the rapid growth of the plant 
seldom fails, notwithstanding its aggressors, to insure its being 
brought to a crop. 
The third head of enquiry was—how far the depredations of the 
insect were dependant upon the weather. The opinion of the great 
majority of correspondents is, that the fly is most to he dreaded in 
hot weather. 
With regard to soils, the fourth head of enquiry was—whether 
any of the varieties with which this country abounds, are safe from 
the visits of the insect. On this point the correspondents agree, that 
no soils whatever, on which turnips can be cultivated at all, are safe 
from its natural enemy. On strong lands as well as light lands, on 
hot soils as well as cold, the turnip fly will be found. 
On the fifth head of inquiry—how far the use of particular kinds 
of manure may affect the appearance of the insect—it seems to he 
ascertained, that no manure at present known, will prevent its ap¬ 
proach ; but that, whatever manure may be used, the fly will not 
avoid it. Apparently dwelling upon this fact, many of the cor¬ 
respondents assert, that it makes no difference what manure is used ; 
hut the observation of others—and by far the greater number—brings 
them to the conclusion, that whatever manure most effectually pro¬ 
motes the growth of the plant, that will at the same time, be the 
most effectual defence from the insect. 
As to the benefits with reference to the turnip fly, arising from 
particular methods of cultivation—which comprises the sixth head of 
enquiry-something is necessary to be said. It was made a distinct 
question in the Circulars, whether the broadcast or drill system was 
most safe from the fly, and the answers have been, what might have 
been anticipated, lriost overwhelmingly in favour of the drill system. 
We must now turn to the most difficult part of our enquiry—the 
natural History of the Insect. Mr. Henderson states, “ The insect 
commonly known by the name of the turnip fly, is Haltica nemo- 
rum, it belongs to the order Coleoptera, and is, therefore, not a fly* 
