428 Habits of the Onion Fly, 



die, and others of a larger size are then observed to decay 

 in a similar manner ; and this continues until the middle of 

 July, and even until the onions are full grown, at M^hich time 

 they have occasionally sufficient strength to survive the injury, 

 with the decay of a portion only of the outer layer or coat : the 

 centre part remaining sound. In this manner whole beds are 

 destroyed ; and it seems to be of little use to sow again, as the 

 fresh-sown plants do not fare better. In light soils, especially, 

 the attacks of this insect are occasionally very annoying to the 

 gardener. 



On stripping off the coats of the young onions, which show 

 evident signs of decay, it is at once perceived that it is owing 

 to the attack of a small apod [legless] grub upon the vital 

 parts of the young bulb or stem of the plant, that its destruc- 

 tion has been occasioned. On pulling up a very young onion, 

 its interior is found to be completely devoured by a single 

 grub at its very heart, but in plants of larger growth I have 

 counted at least half a dozen of these grubs, varying con- 

 siderably in size. They are of a moderately long cylindrical 

 form, pointed at one end, which is the head, and this is fur- 

 nished with two minute tentacula ; the other end is the broader, 

 and is obliquely truncated, with the edges rugose, and with 

 two small reddish spots, from which appear to proceed two 

 internal and dark-coloured veins : the body is smooth and 

 shining, and of a whitish colour. When full grown, they 

 much resemble the common maggots of the flesh-fly, and are 

 nearly half an inch in length. In the summer season they 

 are about a fortnight in arriving at their full growth. They 

 generally consume the entire of the interior of the onion, the 

 outside skin of which is alone left dry and entire, serving as 

 a place in which they undergo their transformations, without 

 forming any cocoon, or without shedding their outer skin ; the 

 skin of the larva, in fact, shortening gradually, and assuming 

 an oblong oval form, rather truncate at the posterior extremity, 

 within which the real pupa is to be found. This puparium, 

 as it may be termed, is of a chestnut colour, having its pos- 

 terior end blackish, with the extremity red, and two large 

 black spots observed in the larva : the oral tentacula are also 

 observable at the other end, they being somewhat exserted. 



In about another fortnight the perfect fly makes its appear- 

 ance. It is a dipterous insect, belonging to the family Mus- 

 cidse, and genus Anthomyia ; and appears to have been noticed 

 by Linnaeus under the name of ilfusca radicum ; it is the 

 Scatophaga ceparum of Kirby and Spence *, which is referred 



* Anthomyia radicum Meig. Zw. v. 168. Linn.ii. 992. ; (ilfusca) brassicae 

 Wicd. Z. MA. 78. ; (Anthomyia) Scatophaga ceparum K. and S. i. 192. 



