102 Insects most injurious to Cultivators : — 



10. Have you ever made any observations as to the mode in 

 which the turnip fly is generated? State what these observations 

 have led to. 



11. Is it your opinion that the fly is more prevalent now than 

 it used to be? If so, can you account for this, and how ? 



12. State any general observations you may wish on this 

 subject. 



In answer to these queries, an extensive series of replies were 

 received from more than a hundred persons, chiefly intelligent and 

 extensive farmers, from different parts of the country, from York- 

 shire to Cornwall ; from which it appears that no sooner does the 

 plant make its appearance above ground, than it is attacked by 

 the insect iii the ■perfect state ; and the first, or cotyledon, leaves 

 being devoured, the plant immediately dies. The case is the 

 same whether the crop be sown early or late ; the insect being 

 in full activity from April to September, and even earlier than 

 the former, and later than the latter, month. Hence, as the 

 chief time for eff'ectively sowing the crop is from about mid- 

 sunmier until the end of July, it is evident that an alteration of 

 the period for sowing, so as not to coincide with the time of the 

 appearance of the insect, cannot be adopted. The answers like- 

 wise show that hot seasons are favourable for the increase of the 

 insect ; and wet ones equally obnoxious to its developement. In 

 like manner, it is equally ascertained that it continues its attacks 

 upon the plant after the expansion of the rough leaves. 



It will be observed, that the preceding observations, and the 

 replies obtained in answer to the queries above given, refer only 

 to the insect in its perfect state, and that neither contain any 

 information as to the earlier stages of the insect's life ; although 

 it is evident that, as it must undergo the changes to which other 

 coleopterous insects are subject, and must consequently pass 

 through the larva and pupa states, a considerable time must be 

 occupied before the perfect beetle appears in the state in which 

 its attack upon the young leaves is made. There is not the least 

 shadow of ground tor supposing that this is not the case, or for 

 adopting the opinion expressed by Mr. Sutton in a pamphlet 

 which has obtained great celebrity ; namely, that the egg is de- 

 posited in the ground, and that exposing it to the influence of 

 the sun and air is the immediate cause of the vivification of the 

 perfect beetle. Mr. Sutton, in pursuance of this doctrine, 

 directs the preparing of the fallows for the seed, and then leav- 

 ing the land for ten days or a fortnight, whereby, for want of 

 proper exposure, the egg is supposed to be destroyed. This 

 opinion is, however, so unquestionably erroneous, that, if success 

 has followed the adoption of the plan founded thereupon, it must 

 certainly have been caused by other and incidental causes. 



Another gentleman, whose conununications are published. 



