Fly, or Musca, L. an order of insects divided into several genera, of which we shall notice only those species that are more immediately connected with agriculture and domestic economy.

1. The Dolphin, or Bean-fly. See vol. I. p. 205.

2. The Corn, or Hessian-fly, a native of the Landgravate Hesse, whence it has received its name. This insect is particularly destructive to wheat-corn, in which it deposits its eggs close to the ground, while growing. - When the young vermin are hatched, they continue for some time in a worm-state, feeding on the tender part of the stalk, the growth of which is thus effectually checked. The Hessian-fly committed great depredati in in the Eastern counties of England, several years since ; and, in the year 1787.. did incalculable damage in the provinces of Pennsylvania and Maryland, in America. The only efficacious remedy hitherto discovered, consists in facilitating the vigorous growth of the plants, by properly manuring and cultivating the soil; which practice, as it will admit of late sowing, will greatly retard their progress.

3. The Turnip-fly, which not only infests turnips, but also cabbages, flax, and other useful vege tables. In order to prevent the depredations of this insect, it has been recommended to mix three pounds of turnip-seed with one ounce of flour of sulphur in a glazed earthen pot, which should be closely covered: after standing twenty-four hours, another ounce of sulphur should be added, and the same quantity after forty-eight hours, so as to employ three ounces of this powder to three pounds of the seed, carefully stirring the whole every time the vessel is opened, with a smooth piece of wood or ladle, that the seed may be thoroughly impregnated with the sulphur. It is then to be sown on an acre of ground, in the usual manner, where it will effectually keep off the insect till the third or fourth seeding-leaf is formed, which will acquire a bitterish taste, and thus be secured from the depredations of the fly. - Another remedy is, to strew tobacco-dust over the land ; and in some counties the seeds are steeped in soot and water for several hours previously to being sown, by which they acquire such a degree of bitterness, as to screen them completely against the ravages of this noxious insect.

There is a kind of fly which infests orchards, perforating the leaves of the trees, especially quinces ; and which, though the foliage is afterwards renewed, oc-casions irreparable injury to the fruit. With a view to prevent these depredations, it has been recommended to mix a small quantity of diluted honey with some arsenic, which composition attracts the insects, and consequently destroys them. This remedy may, with due precaution, also be employed in houses where flies abound ; and as flies axe liable to great thirst, if a weak solution of arsenic with a little sugar be placed on a plate, in windows or on chimney-pieces, they will drink it eagerly, and thus meet with almost im-mediate destruction.

As, however, arsenical remedies' are liable to produce dangerous accidents, we shall communicate other means which are less hazard-ous, and equally efficacious, for exterminating flies. If a room be swarming with these noisome in-sects, the most easy mode of expelling them is, simply, by fumigating the apartment with the dried leaves of the gourd (Cucurbita, L.) the smoke of which instantly expels them, if the window be opened, or suffocates them in a close room; but, in the latter case, no person should remain within doors, as these narcotic fumes are apt to occasion the head-ach. In situations where this expedient cannot be conveniently adopted, Professor Tromsdorf has furnished us with an excellent remedy, that neither endangers the lives of children, nor is attended with much expence or trouble. Take two drams of the extract of quassia, dissolve it in half a pint of boiling water, add a little syrup or sugar, and pour the mixture on plates : to this enticing food flies are extremely partial; and it is to them not less fatal than solutions of arsenic.