CARDUUS. Welted Thistles [Asteraceae]

Twelve species of Carduus are recorded in Britain. These include the native Musk Thistle (C. nutans), Slender Thistle (C. tenuiflorus) and Welted Thistle (C. crispus).

Two Diptera miners, the agromyzids Phytomyza continua and Phytomyza spinaciae are recorded on Carduus in Britain.

The anthomyiid Pegomya steini is recorded on Carduus by Ackland in Chandler (1978), although it is not clear whether the host association is British or Foreign it is included in the key below.

Elsewhere the agromyzids Chromatomyia horticola, Chromatomyia syngenesiae, Liriomyza huidobrensis, Liriomyza strigata, Phytomyza cirsii, Phytomyza continua and Phytomyza spinaciae; the sciarid Phytosciara halterata; and the anthomyiid Pegomya steini are recorded mining Carduus.

Elsewhere the agromyzids Melanagromyza aeneoventris and Napomyza lateralis are recorded boring the stems of Carduus.

Two non-Diptera mines, Scrobipalpa acuminatella and Coleophora paripennella , are recorded on Carduus in Britain (see below).

Elsewhere five additional British non-Diptera miners are recorded on Carduus (see below).

A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Carduus is provided in Bladmineerders van Europa. This includes Agromyza apfelbecki, Chromatomyia 'atricornis', Liriomyza bryoniae, Liriomyza strigata, Pegomya steinii, Phytomyza cirsii, Phytomyza continua, Phytomyza spinaciae, Agonopterix arenella, Agonopterix propinquella, Agonopterix subpropinquella, Apterona helicoidella, Apteropeda orbiculata, Coleophora peribenanderi, Orthochaetes insignis, Scrobipalpa acuminatella, Sphaeroderma testaceum and Sphaeroderma rubidum but not Agonopterix carduella, Apterona helicoidella, Cnephasia stephensiani, Coleophora follicularis, Coleophora paripennella, Phytosciara halterata, Phytosciara macrotricha or Tebenna micalis.

N.B. The key to mines below includes mines recorded on Carduus and Carlina (Asteraceae).

Note: Diptera larvae may live in a corridor mine, a corridor-blotch mine, or a blotch mine, but never in a case, a rolled or folded leaf, a tentiform mine or sandwiched between two more or less circular leaf sections in later instars. Pupation never in a cocoon. All mining Diptera larvae are leg-less maggots without a head capsule (see examples). They never have thoracic or abdominal legs. They do not have chewing mouthparts, although they do have a characteristic cephalo-pharyngeal skeleton (see examples), usually visible internally through the body wall. The larvae lie on their sides within the mine and use their pick-like mouthparts to feed on plant tissue. In some corridor miners frass may lie in two rows on alternate sides of the mine. In order to vacate the mine the fully grown larva cuts an exit slit, which is usually semi-circular (see Liriomyza huidobrensis video). The pupa is formed within the hardened last larval skin or puparium and as a result sheaths enclosing head appendages, wings and legs are not visible externally (see examples).

1a > Leaf-miner: Long narrow interparenchymal mine, greenish. Pupation in leaf at end of mine. Puparium white

Mines of Phytomyza spinaciae on Cirsium arvense Image: Willem Ellis (Bladmineerders van Europa)

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 continental Europe, range extending to the Kirghiz Republic of the [former] U.S.S.R.

Phytomyza spinaciae Hendel, 1928 [Diptera: Agromyzidae].

1b > Leaf-miner: 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.

On Carduus and Centaurea in Britain. On Arctium, Carduus, Cichorium and Cirsium elsewhere. Widespread in Britain and continental Europe.

Phytomyza continua Hendel, 1920 [Diptera: Agromyzidae].

1c > Leaf-miner: Large, very transparent blotch, with primary and secundary feeding lines. In the centre a concentration of black frass. Mines can coalesce, and then contain several larvae. At the start of the mine, at the leaf underside, a white egg shell. However, the larva can leave its mine and restart elsewehere, therefore mines without an egg shell may occur as well

Mine of Pegomya steini on Cirsium vulgare Image: Willem Ellis (Bladmineerders van Europa)

On Carduus, Carlina, Cirsium and Cynara in Britain and elsewhere, although British records on Carduus and Carlina are ambiguous. Distibution in Britain unknown. Widespread in continental Europe.

Pegomya steini Hendel, 1925 [Diptera: Anthomyiidae].

Key for the identification of the mines of British non-Diptera recorded on
Carduus

Note: The larvae of mining Coleoptera, Hymenoptera and Lepidoptera may live in a corridor mine, a corridor-blotch mine, a blotch mine, a case, a rolled or folded leaf, a tentiform mine or sandwiched between two more or less circular leaf sections in later instars. Larva may pupate in a silk cocoon. The larva may have at least six legs (although they may be reduced or absent), a head capsule and chewing mouthparts with opposable mandibles (see video of a gracillarid larva feeding). Larvae of Hymenoptera and Lepidoptera usually also have abdominal legs (see examples). Frass, if present, never in two rows. Unless feeding externally from within a case the larva usually vacates the mine by chewing an exit hole. Pupa with visible head appendages, wings and legs which lie in sheaths (see examples).

1a > Miner and case bearer: The larva lives outside the mine, protected by a case, and feeds on the underlying plant tisses via a hole cut in the epidermis. Mine does not contain frass (Coleophora species)

2

1b > Miner, but not a case-bearer, although it may live sandwiched between two more or less circular sections cut from the leaf in later instars e.g. Incurvaria species. The larva lives mainly inside the mine. Mine usually contains frass

3

2a > Leaf-miner and case-bearer: Larva mines leaves. On Eupatorium the case is extended at the anal end by adding silk and widened by cutting a ventral gusset. On Inula the case is firstly extended by adding rings of leaf-cuticle at the oral end, before reverting to the method used when on Eupatorium. The full-grown case is 10 mm long (British leafminers). A slender tubular silken case, about 10 mm long, straw coloured, three valved. Mouth angle about 30° (Bladmineerders van Europa).

Recorded on Cirsium, Eupatorium, Inula and Pulicaria, but not yet on Carduus, in Britain and Achillea, Anthemis, Carduus, Cirsium, Eupatorium, Inula, Leucanthemum, Pulicaria and Tanacetum elsewhere. Widespread in England. Also recorded in Republic of Ireland. Widespread in continental Europe.

 

Coleophora follicularis (Vallot, 1802) [Lepidoptera: Coleophoridae].

2b > 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).

Recorded on Arctium, Centaurea, Cirsium, Serratula, but not yet on Carduus, in Britain and Arctium, Carduus, Centaurea, Cirsium, Saussurea and Serratula elsewhere. Widespread in Britain, Ireland and continental Europe.

Coleophora paripennella Zeller, 1839 [Lepidoptera: Coleophoridae].

2c > 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).

Recorded on Arctium, Carduus and Cirsium in Britain and Arctium, Carduus, Carlina, Centaurea and Cirsium elsewhere. England, Wales and southern Scotland. Also recorded in the Republic of Ireland. Widespread in continental Europe.

Coleophora peribenanderi Toll, 1943 Lepidoptera: Coleophoridae].

3a > Leaf-miner: 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).

Recorded on Cirsium arvense and Cirsium vulgare, but not yet on Carduus, in Britain plus Arctium, Carduus, Centaurea, Cynara, Mycelis and Serratula elsewhere. Widespread in Britain and continental Europe.

Agonopterix propinquella (Treitschke, 1835) [Lepidoptera: Depressariidae].

3b > Leaf-miner: Rather long full depth corridor that winds freely through the leaf and may cross itself. In the end the corridor widens considerably. Frass mostly in a narrow central line, but may also be deposited along the sides or be missing. The larvae regular leave a mine to restart elsewhere. Pupation outside the mine. Neither larva or mine can be distinguished from that of related species (Bladmineerders van Europa).

Recorded on numerous genera and species in several plant families, but not yet on Carduus, in Britain. Recorded on numerous genera and species in several plant families, including Carduus genevensis and Ajuga reptans, elsewhere. Widespread in Britain and continental Europe.

 

Apteropeda orbiculata (Marsham, 1802) [Coleoptera: Chrysomelidae].

3b > Leaf-miner: Rather narrow corridor, untidy and sometimes branched, starting from the base of the leaf, in particular the midrib. Sides of the corridor irregularly eaten out, not really parallel. Frass mostly present, and then in a central line. The legless larva is capable of leaving the mine and start a new one elsewhere. These later mines are much broader, and the frass is scattered irregularly. (Bladmineerders van Europe. Larva without abdominal legs.

Host plants unknown in Britain. Recorded on numerous genera and species in several plant families, including Carduus, elsewhere. Recorded in southern England. Widespread in continental Europe.

Orthochaetes insignis (Aube, 1863) [Coleoptera: Curculionidae].

3c > Leaf-miner: 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).

Recorded on Artemisia, Carduus, Cirsium and possibly Tussilago in Britain and Carduus and Cirsium elsewhere. Records from Carlina vulgaris and Tussilago farfara are probably incidental. Widespread in Britain and continental Europe.