Agriculture Reference
In-Depth Information
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Fig. 249
Larva of a small narcissus fly,
Eumerus
strigatus
(x7).
and other suitable underground parts of host
plants. Fully fed larvae usually pupate in the
neck region of infested bulbs, and adults of a
second generation appear in mid-summer. Lar-
vae of the second generation become fully grown
by the autumn. They then enter the surrounding
soil where they overwinter; pupation occurs in
the spring.
DESCRIPTION
Adult
5-6 mm long, mainly black with a golden
sheen on the head and thorax;
thorax
with whit-
ish longitudinal lines;
abdomen
with three pairs
of white, crescent-shaped marks;
pterostigma of
forewing
yellow or light brown.
Egg
0.7 mm
long, elongate, white.
Larva
up to 9 mm long;
dirty yellowish-white;
posterior respiratory cone
reddish-brown and elongated
(Fig. 249).
Puparium
6-7 mm long, dirty yellowish-white;
posterior respiratory cone
reddish-brown and
elongated
(Fig. 250).
Fig. 250
Puparium of a small narcissus fly,
Eumerus
strigatus
(x7).
guishable from those of
Eumerus strigatus
(above) by the dark brown or blackish
pterostigma.
Merodon equestris
(F.)
Large narcissus fly
The large narcissus fly is mainly a pest of daffodil
and narcissus; various other ornamental bulbs,
but not tulip, are also attacked. The inner tissue
of larva-infested bulbs is destroyed and the re-
sulting cavity becomes filled with rotting tissue
and blackish frass. Infested bulbs feel soft, espe-
cially in the neck region. If planted, damaged
bulbs give rise to weak, discoloured and dis-
torted foliage and poor-quality flowers; some-
times, growth is limited merely to the emergence
of a ring of narrow, grass-like leaves. Although
widely distributed, in the British Isles this pest is
of most significance in southwestern England.
BIOLOGY
Unlike species of
Eumerus
(p. 177
et seq.),
the
large narcissus fly is univoltine, and adults are
active in calm, sunny weather at any time from
late April to July. Eggs are laid singly on the
neck of a bulb or in the soil, especially where the
egg-laying female can gain access through a soil
crevice; the eggs may also be laid low down upon
withering foliage of host plants. Eggs hatch in
approximately 2 weeks, and each neonate larva
Eumerus tuberculatus
Rondani
A small narcissus fly
This species is associated mainly with diseased or
decaying narcissus bulbs. The larvae cause con-
siderable damage and often completely destroy
attacked bulbs. However, since infestations
rarely if ever occur on healthy bulbs, the insect is
of only secondary importance. Adults are distin-
