HOLCUS. Yorkshire-fog and Creeping Soft-grass. [Poaceae]

Four species of Holcus are recorded in Britain. These include the native Creeping Soft-grass (H. mollis) and Yorkshire-fog (H. lanatus).

Thirteen Diptera miners, the agromyzids Agromyza albipennis, Agromyza mobilis, Agromyza nigrella, Agromyza nigripes, Cerodontha denticornis, Cerodontha flavocingulata, Cerodontha pygmaea, Chromatomyia fuscula, Chromatomyia milii, Chromatomyia nigra, Liriomyza flaveola, Liriomyza phryne and Pseudonapomyza atra, are recorded on Holcus in Britain. Miners on grasses should be reared, whenever possible, to confirm their identity.

Three of these, Agromyza mobilis, Agromyza nigrella, Agromyza nigrella, Cerodontha denticornis, Cerodontha incisa, Cerodontha muscina, Cerodontha pygmaea, Chromatomyia milii and Chromatomyia nigra are also recorded on Phleum in Britain.

Records of the agromyzid Chromatomyia fuscula on Holcus (Robbins, 1989 and 1991) are rejected as this species is not British.

Elsewhere the agromyzids Agromyza mobilis, Agromyza nigrella, Cerodontha incisa, Cerodontha flavocingulata, Cerodontha muscina, Chromatomyia fuscula, Chromatomyia milii, Chromatomyia nigra, Liriomyza flaveola, Metopomyza flavonotata and Pseudonapomyza atra, and the ephydrid Hydrellia griseola are recorded mining Holcus.

Eight British non-Diptera miners are recorded on Holcus in Britain (see below).

Elsewhere four additional British non-Diptera miners are recorded on Holcus (see below).

A key to the European miners, based on characteristics of the mines, immature stages and where relevant the larval cases, recorded on Holcus is provided in Bladmineerders van Europa. This includes Agromyza mobilis, Agromyza nigrella, Agromyza nigripes, Cerodontha denticornis, Cerodontha flavocingulata, Cerodontha incisa, Cerodontha muscina, Cerodontha pygmaea, Chromatomyia fuscula, Chromatomyia milii, Chromatomyia nigra, Hydrellia griseola, Liriomyza flaveola, Liriomyza phryne, Metopomyza flavonotata, Pseudonapomyza atra, Coleophora lixella, Elachista albifrontella, Elachista apicipunctella, Elachista argentella, Elachista bifasciella, Elachista canapennella, Elachista chrysodesmella, Elachista dimicatella, Elachista freyerella, Elachista hedemanni, Elachista herrichii, Elachista humilis, Elachista maculicerusella, Elachista nobilella, Elachista pullicomella, Elachista rufocinerea, Elachista subnigrella, Elachista unifasciella but not Coleophora ornatipennella.

N.B. The key to mines below includes mines recorded Holcus and Phleum (Poaceae).

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

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

2 > Leaf-miner and case-bearer: The young larva eats the receptacle out of a floret of Acinos arvensis, and uses the calyce as its first case. Even before the onset of winter it switches to grasses. The larva then lives in an ochraceous, bivalved, tubular leaf case of c. 9 mm, with a mouth angle of c. 25° (Bladmineerders van Europa).

Recorded on Bromopsis, Dactylis, Holcus, Koeleria, Phleum and Poa in Britain and 'grass species' elsewhere. West Norfolk and West Suffolk in Britain. Unknown elsewhere.

Coleophora tricolor Walsingham, 1899 [Lepidoptera: Coleophoridae].

3a > Leaf-miner: The larva mines from the grass tip downwards and the mine occupies half or the whole of the leaf blade width. A whitish blotch is formed with characteristic narrow streaks of frass (British leafminers). Full depth blotch, slightly inflated, descending from the leaf tip, occupying half or the entire width of the blade. The larva may move and make a new mine elsewhere. In the latter case the mines are fairly short; otherwise an entire blade may be mined out. Frass in a some narrow greyish brown streaks. Pupation outside the mine (Bladmineerders van Europa).

Recorded on Dactylis, Deschampsia and Holcus in Britain plus Luzula, Agrostis, Alopecurus, Arrhenatherum, Avena, Avenula, Brachypodium, Bromus, Calamagrostis, Elymus, Festuca Koeleria, Phalaris, Phleum, Poa, Trisetum and Triticum elsewhere. Widespread in Britain, Ireland and continental Europe.

Elachista albifrontella (Hübner, 1817) [Lepidoptera: Elachistidae].

3b > Leaf-miner: Corridor widening while descending from the tip of the leaf. The mine is unusual because the sides are very irregularly scalloped out. Moreover, the mine is not evenly transparent, but rather yellowish green and motly, because the larva leaves patches of parenchyma uneaten, and does not feed full depth. Frass in a few irregular, interrupted length lines. Often 2-3 larvae in a mine. The larvae hibernate in the centre of the mine; after winter they leave their mine and pupate ( Bladmineerders van Europa).

Recorded on 'various grasses', but not yet on Holcus, in Britain plus Luzula, Agrostis, Arrhenatherum, Brahcypodium, Calamagorstis, Dactylis, Deschampsia, Elymus, Festuca, Glyceria, Holcus, Melica, Milium and Poa elsewhere. Widespread in Britain, Ireland and continental Europe.

 

Elachista apicipunctella Stainton, 1849 [Lepidoptera: Elachistidae].

3c > Leaf-miner: In autumn the larva makes a narrow corridor a few cm in length, in which it hibernates. In March it moves to a new leaf. Here a transparent, full depth mine is made that descends from the leaf tip, and occupies the entire width of the blade. Most frass is concentrated in the oldest, highest, part of the mine. The larva may leave its mine and restart elsewhere. Pupation outside the mine

Mine of Elachista argentella on Dactylis glomerata Image: Ben Smart (British leafminers)

Recorded on Dactylis glomerata, but not yet on Holcus, in Britain. Recorded on numerous grasses including Holcus elsewhere. Widespread in Britain and continental Europe. Also recorded in the Republic of Ireland.

Elachista argentella (Clerck, 1759) [Lepidoptera: Elachistidae].

3d > Leaf-miner: Flat, whitish. Pupation outside the mine (Bladmineerders van Europa).

Recorded on Holcus mollis in Britain plus Agrostis, Arrhenatherum, Avenula, Deschampsia, Festuca and Poa elsewhere. Widespread in Britain and continental Europe.

Elachista canapennella (Hübner, 1813) [Lepidoptera: Elachistidae].

3f > Leaf-miner: Long, flat, whitish, relatively broad corridor descending from the leaf tip. Frass irregularly scattered. The larva may make several mines during its lifetime. Pupation outside the mine (Bladmineerders van Europa).

Recorded on Dactylis, Holcus and Poa in Britain plus Agrostis, Bromus, Festuca, Holcus, Koeleria, Trisetum and Triticum elsewhere. Widespread and reasonably common throughout much of the British Isles except the very far north. Widespread in continental Europe.

Elachista freyerella (Hübner, 1825) [Lepidoptera: Elachistidae].

Recorded on Brachypodium, Dactylis and Holcus in Britain and Brachypodium, Dactylis and Melica elsewhere. Distributed in southern England and Wales and also occurring in parts of northern England and Ireland. Widespread in continental Europe.

 

Elachista gangabella Zeller, 1850 [Lepidoptera: Elachistidae].

3f > Leaf-miner: In spring a short corridor is made that is almost stuffed with frass. After hibernation this mine is vacated, and the larva then makes a number of elongated blotches, all descending from the leaf tip. These latter mines are whitish, with irregularly scattered frass (Bladmineerders van Europa).

Recorded on Carex, Agrostis, Anthoxanthum, Deschampsia, Festuca, Holcus and Poa in Britain plus Phalaris elsewhere. Widespread in Britain, Ireland and continental Europe.

Elachista humilis Zeller, 1850 [Lepidoptera: Elachistidae].

3h > Leaf-miner: Larva makes a large whitish blotch and mines the leaf downwards. The frass tends to be deposited in the upper part of the mine (British leafminers). Oviposition usually not far from the leaf tip. From there descends an irregular blotch mine. Hering (1957a) describes the mine as flat and quite shallow, giving it a greenish, rather than whitish appearance. Frass initially in the oldest, upper part of the mine, later in strings. The larva can leave its mine and restart elsewhere. Normally only one larva per mine, but sometimes two or even three mines in a leaf. Pupation outside the mine (Bladmineerders van Europa).

Recorded on Dactylis, Phalaris, Phragmites and Poa, but not yet on Holcus, in Britain plus Agrostis, Alopecurus, Arrhenatherum, Brachypodium, Calamagrostis, Elymus, Festuca, Holcus, Trisetum and Triticum elsewhere. Widely distributed in Britain, Ireland and continental Europe.

Elachista maculicerusella (Bruand, 1859) [Lepidoptera: Elachistidae].

3i > Leaf-miner: The larvae feed on a range of grasses, causing whitish mines on the blades (UKMoths). Flat, translucent mine that can either run or down; the width may vary too, can be as wide as the blade. Frass few, grey, dispersed. The larva makes several mines (Bladmineerders van Europa).

Recorded on Arrhenatherum, Festuca, Holcus and Phleum in Britain and Arrhenatherum, Festuca and Holcus elsewhere. Widespread in Britain and continental Europe. Also recorded from the Republic of Ireland.

 

Elachista rufocinerea (Haworth, 1828) [Lepidoptera: Elachistidae].

3j > Leaf-miner: Narrow, flat, corridor descending from the leaf tip. Frass in an almost continuous line. The larva usually makes several mines. Mines pale yellow green at first, turning purple later. Pupation external (Bladmineerders van Europa).

Recorded on Bromopsis erecta and Avenula pubescens, but not yet on Holcus, in Britain and Avena, Bromopsis, Calamagrostis, Dactylis, Festuca, Avenula and Holcus elsewhere. Southern England. Widespread in continental Europe.

 

Elachista subnigrella Douglas, 1853 [Lepidoptera: Elachistidae].

3k > Leaf-miner: In autumn the larva makes a long, somewhat blistered, slightly transparent corridor. In spring it mines the basal leaves that lie on the ground. These mines are swollen, clouded green, opaque, and the mined tips of the leaves are puckered and shrunken, filled with frass (Bladmineerders van Europa).

Recorded on Brachypodium and Dactylis, but not yet on Holcus, in Britain and Brachypodium, Dactylis, Avenula, Holcus and Milium elsewhere. Recorded from North Essex, North Hants and South Essex in Britain. Widespread in continental Europe.