Amongst many flies with bodies favoured with a brilliant metallic sheen, several species of green-bottle flies (_Luciliæ_) are notorious. Of these latter _L. Cæsar_ is the most common, but _L. Sericata_ is by far the worst in England, not uncommonly laying eggs upon sheep; many are of a brilliant golden green, but some vary towards a coppery green; all have red eyes and silvery faces. In summer-time these flies seize every opportunity of depositing their eggs upon any sores or skin wounds of animals; their larvæ normally feed on carrion and dung. The green-bottle, like the blue-bottle flies, are fond of both sweets and filth, but they do not pester wholesome animals as do the sweat-flies. Next to the _Muscidæ_ the most often observed and easily recognisable as a distinct family of flies are the _Syrphidæ_, which include the "hover-flies," the drone-flies (often mistaken for the male of the hive-bee), and a number of other very common flies of a generally similar full-bodied shape, in most of which colour stripes and bands more or less suggest a comparison with wasps. The numerous species native to Great Britain are widely distributed, and, excepting the rare and very hairy _Merodon narcissi_, of which the larvæ feed on liliaceous bulbs, none is injurious and some are beneficial. Nearly all the flies of this family frequent flowers. The habit of many to hover for hours about a favoured spot, as if for mere pleasure, is remarkable; but it is not generally recognised that some of these hover-flies (of the genus _Syrphus_) are hawking for winged aphides and other small insects, which they quickly suck dry and drop whilst still on the wing. Many of the flower-frequenting _Syrphidæ_ are great devourers of pollen; all have strongly developed suctorial mouth parts. The larvæ of the various syrphid flies differ greatly in appearance and habit; some are terrestrial; some aquatic; some semi-aquatic; some feed on decadent vegetation; some on sewage and filth, and some are insectivorous. Most useful to the horticulturist are those of the genus _Syrphus_, which feed on green-fly and other aphides. The most curious in shape are the "rat-tail" maggots of the common drone-fly, _Eristalis tenax_ (also others of allied genera), which can extend their long tubular tails and breathe atmospheric air through the same whilst lying under water. The larvæ of the genus _Volucella_ are found dwelling in the nests of bumble-bees and wasps; it is rather uncertain how far they are commensal, or parasitic, or devourers of dead matter. Some of the syrphid flies are single-brooded, but some at least are double or treble-brooded in the year; records are wanting about many, and which, if any other than the common drone-fly, are multi-brooded. Anyhow, none appears to breed in Great Britain as rapidly as do the house-fly, the blue-bottle, and other muscid flies. The larvæ of _Conops flavipes_ are parasitic in the body of the adult bumble-bee, and they pupate therein.