DIPTERA. 495 



tion was made for the discovery of insects in them. Since 

 then, I have been favored by Mr. Westwood with copies of 

 two articles* by him, on the onion-fly {Anthomyia Ccparum), 

 whicli, in the maggot state, lives in the roots of onion plants 

 in Europe, and causes them to wither and perish exactly in 

 the same way as young onions do here. Hence there is good 

 reason to believe that the failure of our onion crop is caused 

 by the ravages of maggots similar to those of the European 

 onion-fly. The latter lays its eggs on the leaves of the onion, 

 close to the earth, so that the maggots, when hatched, readily 

 make their way to the heart of the onion. The maggots come 

 to their growth in about two weeks, turn to pupas within the 

 onions, and come out as flies a fortnight afterwards. We have 

 a kind of fly, corresponding almost exactly with the descrip- 

 tion of the onion-fly. This strengthens my belief that our 

 onions suffer from the depredations of the maggots of this or 

 of a similar insect. The fly to which I allude is often found 

 on windows in the spring. It is ash-colored, with black hairs 

 sparingly scattered on its body. It has a rust-colored forked 

 spot on the top of its head, and three rust-red lines on the 

 thorax; and the wings are tinged with yellow near the shoul- 

 ders. It measures one fourth of an inch in length. It is stated 

 that there are two or three generations of the European onion- 

 flies during the summer, and that the late broods pass the win- 

 ter in the pupa state, and are ready to burst forth at the first 

 warmth of the following spring. It is stated that the onion 

 crop may be preserved from the attacks of this fly, by sowing 

 the seed on ground upon which a quantity of straw has been 

 previously burnt. 



The peculiar disease that has affected potatoes within the 

 last ten years, has been attributed, by many persons, to the 

 depredations of insects. In the course of this work, several of 

 these insects have been described. Another is now to be added 

 to them, as will be seen by the following extract from a letter, 

 received from a correspondent in July, 1851. " A new potato- 



* See the "Magazine of Natural History," Vol. VII., p, 425, and the " Gar- 

 dener's Magazine," Vol. XIII., p. 241. The same insect is also described and 

 figured in KoUar's- "Treatise," p. 157. 



