THE OKION-FLY : EN"EMIES AND PREVENTIVES. 177 



which the habits are as yet unknown, and by several undescribed 

 species that are to be found in our collections. 



It is believed that the larvae of the Golden-eyed flies, of the genus 

 Clirysopa, are of service in destroying the eggs of the onion-fly, as they 

 are known to devour eagerly the contents of similar eggs, and their 

 own eggs attached to their hair-like pedicel, have been frequently seen 

 upon the lower part of onion plants convenient to the eggs of the fly. 



Preventives of Attack. 



Many metliods have been recommended for use against this pest. 

 Several of them will be given, for often it is only by trial of various 

 methods that one may be selected which will prove efficacious in a 

 particular locality. An application which will be entirely successful 

 under one condition of soil may be of no service whatever where the 

 conditions are quite difierent ; and the convenience for obtaining the 

 materials to be employed may also vary greatly with the locality. 



Kollar, in his Treatise on Insects Injurious to Gardeners, Foresters 

 and Farmers, recommends as a preventive strewing the onion-bed with 

 powdered charcoal, leaving small portions without the application, 

 where the flies may deposit their eggs, and the infested onions subse- 

 quently taken up and destroyed by burning or deep burying. 



Dr. Fitch suggests that instead of sowing onion seed in rows, where 

 the young seedlings grown in contact, give every facility for the larvae 

 to pass from one to another, that they should be grown in hills of 

 only three or four seedlings and among other vegetables, so that when 

 the young larvae have consumed one hill, they would be unable to 

 travel through the soil the distance required to find another, and 

 would, therefore, die before maturing. 



Scattering dry, unleached ashes over the beds as soon as the plants 

 are up, while they are wet with dew or from ram, and at intervals 

 thereafter of a week throughout the month of June, has been found 

 serviceable in preventing the deposit of the eggs upon the plants. 



Miss Ormerod, of Dunster Lodge, near Isleworth, England, who, 

 during the past few years, has published severalquite valuable Annual 

 Reports of " Notes and Observations on Injurious Insects," has given 

 in each, such methods for the prevention of the attacks of this fly as 

 have been tested and have yielded the best results. Among them are 

 the following: — 



Pulverized gas-lime scattered among the onions was found to act 

 well in keeping off the insect. 



Watering with the liquid from pig-styes, collected in a tank provided 

 for the purpose, was found to answer still better. 

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