Agriculture Reference
In-Depth Information
Fig. 256
A glasshouse wing-spot fly,
Scatella
sp.
(x15).
Fig. 257
A small fruit fly,
Drosophila
sp. (x15).
also cause concern and can be a nuisance, par-
ticularly when they contaminate pre-packed,
plastic-wrapped food crops such as lettuce; the
flies also soil glasshouse plants with specks of
faecal material. Adults of
Scatella
are often mis-
taken for scuttle flies (see p. 177) or sciarid flies
(see p. 167), but they are readily distinguishable
by the twice-broken costal veins and by the
slightly dusky wings which have several small,
clear patches visible in the membrane
(Fig. 256).
Larvae of
Scatella
are dirty yellowish to dirty
greenish, with a pair of conspicuous, dark-tipped
posterior respiratory tubules (see Fig. 103).
ing the flesh to leave only the skins; larvae may
also act as disease vectors. Adults are c. 3 mm
long and mainly yellowish or yellowish-brown,
with bright red eyes; the abdomen is marked
dorsally with dark brown cross-bands
(Fig. 257).
Larvae are up to 4.5 mm long and whitish, with
laterally protruding anterior spiracles, tube-like
posterior spiracles and distinct black mouth-
hooks. Breeding takes place in various kinds of
rotting vegetable matter. There are several gen-
erations annually and development from egg to
adult takes about 3 weeks.
Family DROSOPHILIDAE
(small fruit flies)
Drosophila melanogaster
Meigen
A small fruit fly
Scaptomyza flava
(Fallen)
Whitish, usually blotch-like, leaf mines formed
by larvae of this often abundant species occur on
various members of the Brassicaceae, including
oilseed rape and vegetable crops such as broc-
coli, Brussels sprout, cauliflower and radish. In
severe cases, infested leaves are killed but any
effect on plant growth is usually of little or no
significance.
This generally abundant fly (best known for its
universal use in cytological, genetical and other
laboratory studies) is sometimes a minor prob-
lem in soft-fruit plantations, orchards and vine-
yards. Most frequently, the flies are merely of
nuisance value, as they are often attracted in vast
numbers to overripe, fermenting fruit and fruit
juices, both indoors and outside. In vineyards,
the larvae sometimes feed on damaged grapes
and may also invade adjacent sound fruit, remov-
BIOLOGY
Adults occur from April onwards and there are
several overlapping generations each year. The
