124 CULTURE OF FARM CROPS. 



tion, and everywhere practicable. The maggot of the midge 

 previous to assuming its larvae condition, buries itself an 

 inch or a little more below the surface of the ground. That 

 when the time arrives for their assuming the fly state, they 

 wriggle themselves to the surface for that purpose. It is 

 only by a series of alternate contractions and expansions 

 of one side and the other that they can make their way up 

 from an inch below the surface to the light and air, for 

 they possess no feet, or other exposed members when in 

 the pupa case. If, therefore, the pupa be buried, say six 

 inches below the surface, it is permanently imprisoned, for 

 nature has not provided any apparatus to enable it to ef- 

 fect its escape under such circumstances. If, therefore, at 

 any time between August and May of the following year, 

 the ground be ploughed to a depth of at least six inches, 

 and in such a way that the furrow slices lie as compactly 

 as possible, there can be no doubt that a vast majority of 

 the pupae will perish from inability to escape from their 

 imprisonment. But how much greater the probability of 

 every individual pupa perishing if the ground be ploughed 

 seven inches deep immediately after harvest, and left un- 

 touched until the follo\ving August 1 Every one knows 

 that it is not possible, in ploughing, to turn a sod or fur- 

 row slice completely over, so that all parts shall be altogether 

 reversed. The furrow slices may be made to lie with great 

 compactness, but there will be interstitial spaces into 

 which the pupa3 may fall or wriggle themselves, and event- 

 ually escape. When the field is ploughed immediately 

 after harvest, not only will the autumnal rains fill the 

 spaces beneath and between the furrow slices by washing 

 down fine particles of earth, but the influence of many 

 months of winter and spring will consolidate the furrow 

 slices, and their compactness may be ensured by rolling 

 in May, or the early part of June, before the fly ap- 

 pears. Rolling the land immediately after ploughing 

 is accomplished, will give further security to the pri- 

 son in which the pupae are inclosed by this simple ar- 

 tifice." 



