THE TURNIP-FLY. 
445 
The enormous losses periodically occuring from the turnip fly, have 
necessarily led to enquiries after the means of prevention or cure. 
Many plans have been tried with partial success; and, from time 
to time, such plans have been published to the world as unerring 
remedies for the disease. A few years trial on an extended scale has, 
however, generally shewn, that such conclusions have been formed 
on too narrow an observation; and that particular circumstances of 
season or locality have produced the effcet, which had been ascribed 
to some general cause, applicable alike to all seasons and places with¬ 
out exception. Nothing but an extended observation, upon most of 
the varieties of soil, and through a course of varying seasons, can 
authorize confidence in any plan, upon a subject so complicated in 
its bearings; and no individual, however, wide his sphere, can be 
safely relied upon, as practically proving the sufficiency of the remedy. 
It will be seen that plans of prevention have been acted upon, under 
which individuals have, as they supposed, for a long series of years 
saved their crops; whilst the plan itself may eventually prove false 
in principle, and seemingly efficacious only from circumstances alto¬ 
gether foreign to it. 
The course pursued by this Society, in obtaining the result of the 
experience of Farmers in different parts of the country, seems most 
adapted to the nature of the enquiry. The conclusions of practical 
men on all soils and under all circumstances are obtained; not only 
made during a few years, but extending through a long series of sea¬ 
sons : whilst the wide range of the enquiry seems to shut out the 
possibility of being misled by partially tried theories. An opportu¬ 
nity is also thus given of ascertaining the general practice as well as 
the oj3inions of intelligent men ; and the certainty and safety of the 
one, is made a corrective of the inevitable vagueness and uncertainty 
of the other. 
Upon the first head of enquiry—as to the seasons in which the de¬ 
predations of the fly occur,—it appears that the greater number of 
correspondents state the months of May and June as the period of 
the first attack. It is, however, generally added, that their appear¬ 
ance occurs as soon as the turnip plant itself appears; and many cor¬ 
respondents have observed the insect upon the crops in April, whilst 
four correspondents have observed them in the gardens as early as 
March, upon garden sown turnips and cabbage plants. 
On the second inquiry,—as to the stage of growth of the plant, in 
which it is subjected to the attack of the fly—the information is 
nearly unanimous. It is well known that as soon as the turnip plant 
appears, and puts out the two first leaves, called the cotyledon leaves. 
