86
REMARKS ON COLLECTING DIPTERA.
Diptera are abundant in nearly every locality in Britain from
early spring until the beginning of winter, and in every conceivable
nature of habitat.
The ordinary gauze butterfly net is the most useful one for cap-
turing them, and a light sweeping net, such as is used by coleopter-
ists, is invaluable for collecting in ditches, from long grass, and places
of a like nature. My plan, when collecting, is to always bring the
specimens home alive, in chip boxes, killing them by the fumes of
burning sulphur.
Diptera should never be wetted or placed in any moist situation,
as the pubescence once matted together usually prevents identifica-
tion. They should be mounted on the Continental "Carlsbad" pins,
of which several sizes are made, Nos. 0 to 4 being the most useful ones.
Very small specimens should be pinned with minute pins, these being
stuck at the end of small oblong pieces of pith, with a No. 4 Carls-
bad long pin through the other end of the pith.
Diptera should not be set, as, unset, they have the following
advantages :—(1) They are not so liable to damage, as the legs and
wings are not spread out. (2) They occupy less space in the cabi-
net, and are easier to handle. (3) They are exchangeable with
Continental correspondents. (4) An immense amount of time is
saved.1 Moreover, when stuck on long pins, a higher magnifying
power may be used on them as they stand in the cabinet, by reason
of their nearness to the glass.
Of the metamorphoses of the Diptera but very little is known
beyond the life-histories of a few common species. Many are car-
nivorous ; large numbers (probably the large majority) breed in
decaying animal and vegetable matter ; others are parasitic on other
insects, generally Lepidoptera, and a few are parasitic on vertebrate
animals.2
Thirty-one families of Diptera are represented in this country,
the number of British species being about 2,400. The following are
the families, but the briefest outline of the characters and habits of
each must suffice, and within brackets I have put the names of the
principal genera included in each division.
Cecidomyidae.—Small, delicate flies, larvae mostly gall-makers.
1 There is a difference of opinion among dipterists on this question of setting ; Mr. Verrall
considers that specimens should be "set" whenever possible; see his remarks further on
(p. 91).—Ed.
2 [The late Mr. A. H. Halliday published a valuable paper on the Metamorphosis of Diptera
in the Nat. Hist. Review, iv., pp. 177-197, pl. xi. (1857). The structure of the larvae and trans-
formations of the parasitic and leaf-burrowing species are well worthy of the attention of micro-
scopists and would prove to be a fruitful field for investigation.—ED.]