Turnip Flea-Beetle. 105 



eggs which have had any connexion with the plant in question ; 

 either as regards the seed of such plant, or the manure in which 

 it is sown. Whence, then, do these perfect insects come ? 

 Everj^ one accustomed to entomological excursions during the 

 winter is acquainted with the fact that the Halticae hybernate in 

 moss, &c. ; whilst it is equally well known that they feed upon 

 other cruciform plants in the spring months, preferring, however, 

 the turnip. It scarcely, therefore, admits of a doubt, that the 

 perfect insects which attack the early leaves of the turnip are 

 insects of the preceding yeai", produced from eggs deposited by 

 parent beetles upon the turnip plants, after they have attained a 

 growth sufficient to be secure from destruction from the attacks 

 of the insects or their grubs. I have traced the metamorphoses 

 of some of the insects belonging to the same family as the 

 Haltica ; and, from analogy, I have little hesitation in consider- 

 ing it as the most probable, that the transformations of these 

 beetles are comparatively rapid. It is thus probable, that the 

 eggs are deposited, the larvae hatched and full-fed, and the 

 transition to the pupa, and, ultimately, to the imago, state, 

 effected in the course of a few weeks ; so that, before the close 

 of the summer, a generation of insects is produced, which are 

 destined, in the following spring and summer, to become the 

 terror of the farmer. Probably the period of the egg state is 

 very short; so that the grubs of various sizes observed by 

 Rusticus were, in all probability, the progeny of the beetles, 

 few in number, observed at the first; whilst the subsequent in- 

 crease in the numbers of the perfect insect may be accounted 

 for, by supposing that the larvae had thus soon attained their 

 perfect state. 



These observations are perfectly in unison with the known 

 economy of some of the insects belonging to the same family as 

 the Haltica : they violate none of the well-known principles of 

 insect economy ; and they offer a clue to the discovery of more 

 successful, because more certain, modes of procedure, with a 

 view to prevent the attacks of the insect. These may be divided 

 into those which have reference, 1st, to the more healthy growth 

 of the plant ; and, 2dly, to the destruction of the insect. With 

 regard to the former, I cannot render greater service than by 

 transcribing the recommendations appended to the Report of 

 the Committee of the Doncaster Association already mentioned, 

 which are as follows : — ■ 



" That, most effectually to insure the speedy growth of the 

 plant, the land should be kept in the best possible state of culti- 

 vation. 



" That the fallow should be completed as early as possible, so 

 as to give an opportunity for choosing a favourable season for 

 sowings. 



