320 Mu II A Kb Y ux iNst:<ri'sJ 



provided no wee<ls of the turnip kind have been mixed with the preceding 

 crop. It eouhl no more subsist in a field of grain than it couhl on a bare 

 fallow. S. It is not in consequence of plants being dibeased that the fly at- 

 tacks them, but because the turnip is its natural food. Insects, as regards 

 their means of subsistence, are subject to the same general la^vs as the rest 

 of the animated creation; some are carnivorous, others herbivorous, while 

 another portion act as scavengers, and clear away nuisances. It is the last 

 that follow in the wake of a disease, and render it more virulent ; but a 

 leaf-eating insect would no more desert the healthy foliage to feed on the 

 contaminated, than a cow or a sheep would turn from the salubrious pas- 

 ture to riot on garbage. In some parts of a field, plants will not be thriv- 

 ing so well, will be less robust, an<l more backward than others, and these 

 will probably perish, while the remainder will surmount the danger. But 

 this feebleness is not disease, but the consequence of insufficient food, and 

 the plant being placed in circumstances unsuited to its growth. Supply the 

 deficiency, or remove the obstacles, and it will bear comparison with the 

 most vigoro\is. The insects select these parts, not as being distempered, 

 but as affording a more tender and palatable fare ; and the plants suffer, 

 not merely from having their strength normally impaired, but from the 

 protracted period in which they are allowed to pine iu an infantile condi- 

 tion. 



The scent of this insect is remarkably keen, and it is by its means that it 

 is attracted to its booty from afar. The poet Thomson represents the in- 

 sect myriads as coming "warping on the eastern winds," to devastate the 

 promise of the opening year ; this insect, however, advances contrary to 

 the breeze which wafts to it the perfume from fields of germinating seed- 

 lings. It is most prevalent in low-lying situations, wliere high hedges 

 or plantations impede the circulation of air; or along the sea-coast, 

 where the temperature is little liable to extremes. It seldom does any 

 hurt on airy and more exposed grounds, and I have known instances, 

 where, for upwards of thirty years, it has not occasioned even partial in- 

 jury. It comes forth most abundantly in the heat of the day ; even iu 

 the midst of winter, several may be seen basking upon a sunny wall. In 

 cold weather it remains torpid and inactive. It has been mentioned, as au 

 instance of its destructive powers, that an individual who confined a few, 

 for the purpose of observing their habits, found that they consumed ten 

 young turnip plants every day,* In the turnip fields, remarks a practical 

 observer, "it is surprising with what rapidity the work of devastation pro- 

 ceeds ; one day blanks will be noticed in the rows of plants of 2 or 3 inches 

 in length, in another day or two these blanks will have extended to a foot ; 

 in a few days more the openings will have increased to 3 or 4 feet; an(l 

 thus in 10 or 12 days the farmer's pro.*pects for plenty of winter food 

 for his flocks is partially or wholly blasted."t Messrs Kirby & Spence state 

 that in the opinion of an eminent agriculturist, the loss sustained in 1780 

 to the turnip crops in Devonshire, amounted to no less than ^100,000 

 from this cause alone. J 



It is chiefly after mild, open winters, and a genial spring, that the tur- 

 nip beetle is so numerous as to create alarm. In wet and mclement sea- 

 sons, and after long droughts, it is scarce. The winter and spring of 

 1847-8, were remarkably favourable to its preservation and rapid produc- 

 tion. It first gave warning of its presence by attacking the beds of tur- 

 nips in gardens, and when these were devoured, the radishes were resort- 

 ed to. It was aided in the work of destruction by Ualtica {Macrocnema) 

 Sperguloe of Gy llenhal,§ a coppery green or brassy tinted insect of the same 



♦ Duncan, Quart. Journal of Agriculture, viii., 354. 

 t Fernie, Garrt, Chron., July 18, 1846, p. 48G. 

 \ Kirby ds Spence, Introduction to Entomology, i., 185. Wilson, Art. Entomology, 

 Encyclopsei^lia Britannica, ix., 18o. 



§ Gyll. Insecta Suecica. iii., 571. Hardy, Berwickshire Naturalists' Club's Proceed- 

 ings, ii., 195. Macrocncma picicornis, Kirby, Stephen's lllu»tration.s of British Ento- 

 mology. Mandibulata, iv.,321. 



