30 



HOW TO RAISE ONIONS. 



THE ONION FLY, Anthomyia Ceparum. 



Fig. 1. 



IN travelling through the county of Essex, N. T., a 

 short time since, particularly along the beautiful plains 

 in the vicinity of the Au-Sable River, I had my atten- 

 tion repeatedly attracted to the withered and sickly 

 appearance of nearly all the fields of onions, through 

 which I passed. Upon inquiring the cause, I was in- 

 variably told that it was the effects of a worm, and 

 that it was extremely doubtful if a single tuber Jn a 

 healthful condition would be obtained in a hundred 

 plants. This excited my curiosity, and on raising the 

 bulbs from the earth, I had little difficulty in recogniz- 

 ing the larva of a Dipterous (two-winged) insect, be- 

 longing to a species which in England, as well as in 

 many other parts of Europe, for the last twenty years, 

 have almost entirely destroyed the onion crops, upon 

 the cultivation of which so considerable an amount of 

 labor and experience have been expended. To such a 

 degree have their ravages extended in those countries, 



Flg.S. 



Fig. 8. 



that the husbandmen have been driven to the necessi- 

 ty of abandoning the culture of this important vegeta- 

 ble, not having yet met with any efficient remedy for 

 the destruction of their enemy. 



Much uncertainty still seems to prevail among ento- 

 mologists respecting the peculiar habits and instincts 

 of this little depredator, and we greatly fear that they 

 will long remain in ignorance, unless some interested 

 and intelligent individual, residing on the spot, and 

 having daiiy access to the plants, shall establish a 

 genes ot practical observations on their habits, and in 



this manner trace them through their various stages 

 of existence, up to the perfect fly. Until this is ac- 

 complished, and not till then, will we with any degree 

 of certainty be able to suggest any reasonable method 

 for effectually removing them. If it be not dona 

 speedily, a knowledge of the prolific manner of their 

 increase, makes it probable that they will, in the course 

 of but a few years, spread <*ver the whole country, and 

 almost, if not entirely, obliterate this highly useful 

 vegetable from our gardens. 



This insect depredator is, I think, undoubtedly the 

 Anthomyia ceparum, of Meigen, or a species so closely 

 allied, as to differ but little from it in any of its 

 hajrits. 



It is shown at e, fig. 1, somewhat magnified, the ac- 

 tual length being indicated by the perpendicular, and 

 the spread of the wings by the horizontal line, below 

 the cut of the fly ; c and d, same fig., show the pupa, 

 from which the insect emerges, c being the natural 

 size, and d magnified. It belongs to the second gen- 

 eral division of the Muscides, that of the Anthomyzides, 

 which is composed of species, all of whom have greatly 

 the appearance of common flies. 



The larva of this insect, a in fig. 2, is about of an 

 inch in length, fleshy, and of a white color. It is of a 

 conical form, with a smooth and shining surface, an<j 

 entirely free from any external superficial appendages. 

 The incisions are finely granulate, and the last and 

 largest segment is obliquely truncated at its base, upon 

 which is placed a surrounding border of eight small 

 knots, or projecting points, as seen at 6, fig. 2, repre- 

 senting the larva magnified. 



The female fly deposits its eggs on the base of the 

 stem near the surface of the ground, which in a few 

 days become hatched, the larvae immediately penetrat- 

 ing between the leaves to the bulb, upon which it 

 preys unseen ; but the effects soon become visible, for 



Fig. 4. Fig. 5. 



the leaves turn yellow, fall prostrate on the ground, 

 and quickly wither away. These are shown in figs. 3 

 and 4. In the course of about two weeks they arrive 



