244 Insects most injurious to Cultivators. 



larva state from May to October, there being, during the period 

 between these months, two or three generations. Hence, it is 

 from this continued generation, and from the period assigned to 

 one brood not agreeing with that of another, that we find grubs 

 of different sizes in the same root. The late broods pass the 

 winter in the pupa state, and are ready to burst fortli at the first 

 warmth of the ensuing spring. In Mr. Major's Treatise on 

 obnoxious Insects, 8<.c., it is stated, that " the maggot of the house- 

 fly, as described on the cauliflowers, in some situations proves 

 an enemy to the onion. It is most probable that the parent is 

 attracted by some disease in the onion, as we often find that, 

 in those onions which are gouted and moulded (terms known 

 amongst gardeners), the bulb is most liable to its ravages." 



Now, it is quite evident, that, in this passage, Mr. Major 

 has confounded at least three distinct species of insects : An- 

 thomyia ceparum, Anthomyia brassicae, and the house-fly 

 (Miisca domestica), if not more, as there are many species of 

 house-flies. That these insects are very much alike is true 

 enough : but that only makes it the more necessary to exercise 

 a scrupulous investigation of their characters ; and this cannot be 

 done without study. It would, indeed, be easy to point out the 

 utter inutility, in many cases, oi'piactical, without scientific, know- 

 ledge ; and, consequently, that, in order to destroy insects effectu- 

 ally, entomology must be extensively studied as a science. I trust, 

 indeed, that the time is not far distant, when this science, as well 

 as botany, shall be made a general branch of education. We 

 have, indeed, to regret that in these matters we are always 

 under the necessity of taking lessons from our neighbours across 

 the water, instead of preceding them. At the present time, M. 

 Victor Audouin, one of the professors of the Jardin des Piantes, 

 is giving a most interesting course of public lectures upon the 

 noxious and beneficial insects of France. 



Another observation may be made upon the passage cited 

 from Mr. Major's work; namely, that I have always found fine 

 healthy plants most liable to the attacks of the fly. Unlike the 

 turnip saw-fly, which, from the brightness of it colour, is at once 

 detected, the onion fly is of such obscure tints, and there are so 

 many distinct species of flies having totally different habits, and 

 yet so much alike, that even professed entomologists have diffi- 

 culty in separating them. Hence, the extirpation of the onion 

 fly is attended with greater difficulty. Salt and ashes have been 

 suggested, when strewn over the ground ; but these are in- 

 effectual, because it is upon the plants that the females settle 

 in order to deposit their eggs, and not upon the ground. 

 Bouche suggests the plan of strewing powdered charcoal {ge- 

 stampfte7i kohlen) over the bed, in which the female flies will 

 deposit their eggs as willingly as upon the onion ; the charcoal 



