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REMARKS ON COLLECTING DIPTERA.
LeptidAe.—Several species common everywhere in spring and
summer (Leptis tringaria and L. scolopacea).
Asilidae.—Powerful, carnivorous flies, pubescent, spiny. Fre-
quent woods (Asilus; Dioctria).
BombylidAE.—Found in dry, warm spots, mostly rare. Several
species closely resemble bees (Bombylius).
Therevidae. — Larvae carnivorous. Frequent sandy spots.
Uncommon (Thereva).
Scenopinidae.—Small, sluggish flies. Three species are British,
one, Scenopinus fenestralis, occurring in London.
CYRTIDAE.—Small, globular, soft flies ; rare. Two species only,
Oncodes gibbosus and Paracrocera globulus.
EmpidAe.—Nearly 200 species are British, occurring generally over
the country in woods and fields. Many species hover in swarms over
the surface of ponds and streams, or under trees. I have taken three
species in Epping Forest, but doubtless fifty or sixty species exist
there. (Empis ; Rhamphomyia ; Hilara).
Dolichopodidae.—Brightly-coloured (usually green), small flies,
of which about 180 species are British (Dolichopus; Porphyrops;
Psilopus).
Lonchopteridae, Platypezidae, and Pipunculidae.—These
three families of small flies are each represented by a few species
occurring in woods, among grass, &c. Lonchoptera lutea is gene-
rally abundant.
Syrfhidae.—Nearly 200 species are British. Brightly-coloured
flies, many species resembling wasps and bees. They fly with a
shrill hum, and hover, apparently motionless, in the air, over flowers.
Common in every locality (Syrphus; Eristalis; Platychirus;
Chilosia ; Chrysotoxum).
ConopiDaE.—More or less uncommon, generally resembling
wasps, the larvae being parasitic on bees (Conops).
Oestridae.—The larvae are parasitic on animals. The species
are mostly rare. I have not seen British specimens of the eight
species except one. Some are recorded from Epping Forest
(Oestrus).
Muscidae.— Nearly half the European Diptera belong to this large
family, which is a well-defined group, divisible into six sub-families :
(1) Tachinidae. Found in dry warm spots; chiefly parasitic on
Lepidoptera (Tachina; Nemoraea; Exorista). (2) Dexidae. Allied