430 Habits of the Onion Fly, 



over, unless we suppose either that the grubs of the fly are 

 liable to a very great difference in their period of develope- 

 ment, whilst in their unhatched state in the egg, or that all 

 the grubs are produced from eggs deposited by the different 

 generations of the fly upon the plants themselves, we can- 

 not account for the constant succession of grubs, or for the 

 very great difference in their size in a single bulb. Again, 

 it seems contrary to our ideas of the proceedings of animals, 

 that a fly should at one period of the year have the instinct 

 to deposit the eggs upon the ripe seed, whilst its descendants 

 should place their eggs at the root of the growing plants ; 

 and yet, if this be not the case, in what state does the fly re- 

 main through the winter? Again there appears a difficulty 

 how the grubs find their way to the centre of a root under 

 ground, if produced from eggs not placed upon the seed, but 



flies, to deposit their eggs in spring. Again, if the eggs were deposited 

 upon the seed, how did it happen that the grubs " were very various in 

 size ? " Again, as there is but one generation of herbivorous beetles in 

 the course of a year, if the eggs of the turnip fly were deposited upon the 

 seed in the autumn, there would be no perfect beetles until the grubs to be 

 hatched from these eggs, in the next summer, had arrived at this state ; and 

 yet Rusticus observes, " I knew from experience that the turnip beetle 

 fed on wild mustard and several other hedge plants ; and, therefore, it was 

 not at all an improbable thing that, when they smelt the fragrance of the 

 fresh-bursting cotyledons of their favourite food " (at which period he had 

 just stated that the grubs were most abundant), " they should skip down 

 from their spring habitations, the hedges, and commence the attack." 



From these remarks I think it will be evident that minute research is 

 as necessary into the economy of the turnip fly, as of that which infests 

 the onions ; and it is under such circumstances that the turnip fly has 

 been selected by the Entomological Society [see p. 3. of the cover of 

 Mag. Nat. Hbt. for July] as the subject of the prize Essays upon noxious 

 insects for the present year, 



[" Turnip-seed, committed to properly prepared ground, makes its ap- 

 pearance on the fourth day. Now, suppose that the eggs of the insects 

 are attached to the seed, as is represented by Rusticus, is it probable that 

 they can be transformed first into grubs, next into chrysalides, and lastly 

 into perfect beetles, in the short space of five, or six, or even fourteen 

 days ? This is for Rusticus to explain ; and it is to be hoped that his de- 

 scription only is erroneous, not his doctrine." This remark is quoted from 

 the British Farmer's Magazine for November, 1833, where an abstract of 

 Rusticus's discovery, and remarks upon it, are presented. In the abstract, 

 Rusticus's statement of the effects of steeping the seeds of turnip in brine 

 is, from misapprehension, misrepresented, but has been corrected in a sub- 

 sequent Number of the same Magazine, by the author of the abstract and 

 remarks. In the Gardener's Magazine^ ix. 505., x. 78., some facts in 

 relation to the habits of the turnip beetle are registered; but the work 

 most likely, it would seem, by its title, to avail the researcher on the habits 

 of this insect, is one about to be published, entitled, " Report of the Don- 

 caster Agricultural Society on the turnip fly, founded on the returns re- 

 ceived from upwards of a hundred gentlemen, cultivating turnips on every 

 variety of soil in the country." 



