Agriculture Reference
In-Depth Information
of a summer generation appear in August and
September. Their larvae feed throughout the
autumn and winter. They pupate in April and
early May, and adults emerge shortly afterwards.
DESCRIPTION
Adult
2.0-2.5 mm long and dull grey;
antennae
black, the arista bearing five or six bristles;
palps
club-like, yellow;
wings
large, hyaline and dis-
tinctly oval.
Larva
up to 6 mm long, whitish and
elongate;
anterior spiracles
absent;
posterior
spiracles
borne on short, pointed, posteriorly
directed processes;
mouth-hooks
with just one
tooth.
Fig. 255
Tip of abdomen of larva of yellow cereal
fly,
Opomyza florum:
(a) posterior spiracle (further
enlarged).
Opomyza germinationis
(L.)
Dusky-winged cereal fly
This generally abundant species is associated
with grasses such as cocksfoot, meadow-grass
and rye-grass; infestations on cereals are uncom-
mon. The centre shoots of infested plants wither
and die but the extent of damage is rarely of
significance. Adults occur from mid-June to mid-
November. Eggs are usually deposited on host
plants towards the end of the season and typi-
cally hatch within a few weeks (cf.
Opomyza
florum,
p. 183). The larvae feed slowly through-
out the winter and finally pupate in the spring;
adults appear in June. Larvae are slightly
smaller, thinner and more pointed anteriorly
than those of
O. florum;
also, the anterior
spiracles are usually 8-lobed and the posterior
spiracles separated by just a shallow depression.
Hydrellia nasturtii
Collin
larva
= Watercress stem miner
Larvae of this species mine within the main
stems of watercress plants but usually do not
enter the pith or attack the growing points. The
effect on plant growth, therefore, is of little or no
significance. Larvae (up to 5 mm long) are whit-
ish and elongate, with distinct ventral swellings
intersegmentally, and with numerous short black
spines on the posterior segments; the body ter-
minates in a pair of short, distinctly pointed,
posteriorly directed respiratory processes. The
larvae feed throughout the winter and complete
their development in the spring. Pupation occurs
in the larval mine, and adults emerge in the
spring.
Family EPHYDRIDAE (shore flies)
Hydrellia griseola
(Fallen)
larva =
A cereal leaf miner
Scatella stagnalis
(Fallen);
S.
tenuicosta
Collin
Glasshouse wing-spot flies
Larvae of this species mine within the leaves of
cereals and grasses. Infested leaves often turn
yellow, commencing at the tip that then withers.
These small, black-bodied flies are often numer-
ous in glasshouses and other protected sites and
sometimes reach pest status. The larvae feed on
algae growing on potting composts and rockwool
growing-media, and on algae developing in
nutrient-film troughs. Development from egg to
adult takes approximately 2 weeks at normal
glasshouse temperatures. Although not directly
damaging to crop plants, the larvae may act as
vectors of fungal diseases. The adult flies may
BIOLOGY
Adults of the first generation appear in the
spring. Eggs are then laid near the base of leaves
and hatch within a few hours. The larvae feed
singly within the leaves. At first the larva mines
towards the ligule and, later, towards the leaf tip.
Pupation occurs within the larval gallery. Adults
