CENTAUREA.
Knapweeds, Star-thistles and Cornflowers. [Asteraceae]
Forty
species of Centaurea are recorded in Britain. These include
the native Common Knapweed (C. nigra), Greater Knapweed (C.
scabiosa) and Slender Knapweed (C. debeauxii) and introduced
Knapweeds, Star-thistles and Cornflowers.
The
agromyzid Liriomyza
trifolii, a polyphagous pest species of ornamental and vegetable
crops occasionally intercepted at UK points of entry, is recorded
on Centaurea and has been found under glass in England and
Wales. All populations have been and continue to be eradicated.
Common
Knapweed Centaurea nigra
The
tephritid Philophylla
caesio is tentatively recorded on Centaurea in Britain.
It is recorded as a petiole miner on Urtica elsewhere.
2>
A distinctive mine, with irregular short lateral offshoots into
leaf blade. Pupation external.
Mines
of Liriomyza strigata on Sonchus. Image: Crown
copyright - courtesy of CSL
On
more than 40 host genera in 15 families in Britain. Widespread
throughout Britain. Also recorded in the Republic of Ireland and
is widespread and common in Europe.
->
Larva feeds along the mid-rib, predominantly on the lower surface
and there is little evidence of gall-like swelling. Pupation takes
place at the base of the midrib. Puparium whitish. Record on Centaurea
requires confirmation.
On
Carduus and Centaurea in Britain. On Arctium,
Carduus, Cichorium and Cirsium elsewhere. Widespread
in Britain and Europe.
On
Carduus, Centaurea, Cirsium and Onopordum in Britain
and in addition Cnicus and Serratula elsewhere.
Only recorded from Warwick and Stafford in Britain. Also recorded
in the Repupublic of Ireland. Widespread in Europe, range extending
to the Kirghiz Republic of the [former] U.S.S.R.
5>
Mine linear, whitish, both upper and lower surface. Pupation internal,
at the end of the mine, with the anterior spiracles projecting through
the epidermis.
Two
highly polyphagous species of Chromatomyia, with indistinguishable
mines, have been recorded in Britain. These are syngenesiae
(Hardy) and horticola
(Goureau). British records of horticola
and syngenesiae
on Asteraceae hosts not based on examination of the genitalia
of reared males are treated here as Chromatomyia
'atricornis'.
On
Centaurea jacea, Centaurea montana, Centaurea nigra and
Centaurea nigra. in Britain and additional Centaurea species
elsewhere. Widespread in Britain and much of Europe.
->
Mine long, distinctly greenish. Pupation in mine. Puparium white
in early generations and black and shiny in autumn
Mine
of Phytomyza autumnalis on Centaurea nigra (Spencer
Collection)
Image: Brian Pitkin
On
Centaurea montana, Centaurea nigra and possibly Cirsium
arvense and Cirsium vulgare in Britain and Centaurea
montana, Centaurea nigra, Centaurea scabiosa, Cirsium arvense
and Onopordumacanthium elsewhere. Widespread in
Britain and Europe.
Leaf-miner
and case-bearer:
A relatively large (12-15 mm), dark brown, lightly curved
two-valved sheath case with a narrow ventral keel. Mouth
angle 30-45 (Bladmineerders
van Europa).
Leaf-miner
and case-bearer:
Larva mines leaves (British
leafminers). The larva builds a case from silk, resembling
a razor shell in appearance. (UKMoths).
The
full-grown case is 12 mm long and blackish-brown (British
leafminers). The full grown larva lives in a blackish
brown trivalved tubular silken case of about 8 mm.
The
mouth angle is 0°-10°, causing the case to lay almost
flat on the leaf (Bladmineerders
van Europa).
Case
of Coleophora paripennella
Image: Charles Baker (British
leafminers)
Leaf-mine:
The mine begins in the midrib, especially in a lower leaf,
extending into the leaf disc, branching irregularly or pinnately,
may also locally be blotch like. The mine is brown and very
transparent. Sides very irregularly eaten out. Frass loosely
dispersed or in a loose central line, buy may also be pressed
against the sides of the corridor. The larva may also leave
the mine and restart elsewhere (Bladmineerders
van Europa).
Leaf-mine:
The larva makes a small full depth blotch, usually in the
leaf tip. Frass concentrated in the centre of the mine (Bladmineerders
van Europa).
Leaf-mine:
The larva makes a large number of untidy full depth mines.
The mines contain hardly or no frass. The opening made by
the larva in the underside of the leaf is irregular roundish,
sometimes more of a slit, large in proportion to the size
of the mine, and usually positioned at the side of the mine.
The larva mines until just before the pupation, that takes
place externally (Bladmineerders
van Europa).
Leaf-miner
and case-bearer:
The larva forms a case, approximately 11-12 mm long, beneath
a thistle leaf, although burdock may sometimes be used.
The shape of the ochreous case varies as, when being enlarged,
it is elongated first, and the girth increased subsequently
(UKMoths).
Yellow-brown
to light grey tubular silken case with darker length lines.
The case is fairly large (up to 17 mm) and very slender.
The rear end is three-valved, the mouth angle about 50°.
The larva feeds at the underside of the leaf (Bladmineerders
van Europa).
Leaf-mine:
The eggs of this species are laid on a leaf, with the larvae
mining the underside of the leaf, until a late instar when
it feeds in a web under the midrib of the leaf, causing
visible blotching on the upperside (UKMoths).
Short,
full depth corridor. The larva relatively long lives as
a miner, but finally leaves the mine and continues living
in spinning along the midrib at the leaf underside, from
where windows are eaten in the leaf (Bladmineerders
van Europa).
Leaf-mine:
The mine is brownish and extends along the midrib, sometimes
branching (British
leafminers).
Oviposition
on top of the midrib. Immediately after emergence the larva
gnaws a cavity in the midrib, and from there an irregular
blotch is made adjacent to the midrib. The larva continues
living in the midrib that is gradully hollowed out, making
from there broad, brownish, full depth excursions in the
blade. The mine contains much frass; most of it is concentrated
in the area immediately bordering the midrib. Older, no
longer occupied parts of the mine often split open. Mines
mainly on the lower leaves. The slender larvae move surprisingly
fast upon disturbance; when they rest (in daytime) they
lie lengthwise in the hollowed midrib. Pupation outside
the mine (Bladmineerders
van Europa).