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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). The BSBI provide a downloadable plant crib for Holcus.

Twenty-nine British miners are recorded on Holcus.

Nearly 100 British miners or possible miners are recorded on grasses in Britain.

A key to the European miners recorded on Holcus is provided in Bladmineerders van Europa.

It is recommended that adults of all miners on grasses be reared to be certain of their identity.

Yorkshire-fog
Holcus lanatus

1o > Leaf-miner: Irregular mine, locally shallow, elsewhere much deeper, giving it a mottled appearance. In broadleaved plants the mine often begins as a blotch with stellate extensions, but sometimes as a very fine, shallow corridor. In grasses the mine often begins in the leaf sheath. The frass is very fine-grained, initially scattered, later in aggregates. The egg is deposited on the plant surface, and the empty egg shell remains visible. But the larvae are able to leave their mine and restart elsewhere, thus mines without an egg shell can be found as well. The larva also leaves the mine before pupation. Pupation takes place in a newly made, small, blotch mine without frass; this mine may be made in another plant (species).

Polyphagpus. On ? Alisma, ? Damasonium, ? Sagittaria, ? Bellis, ? Rorippa, Tropaeolum, ? Lychnis, ? Stellaria, ? Carex, ? Cyperus, ? Scirpus, ? Hydrocharis, ? Stratiotes, ? Lamium, ? Lemna, ? Allium, Arrhenatherum, ? Polygonum, ? Potamogeton, ? Veronica, ? Typha, but not yet on Holcus, in Britain.

On ? Alisma, ? Damasonium, ? Sagittaria, ? Bellis, ? Rorippa, Tropaeolum, Lychnis, ? Stellaria, Carex, ? Scirpus, Trifolium, ? Hydrocharis, Lamium, ? Lemna, Allium, Papaver, Agrostis, Alopecurus, Apera, Arrhenatherum, Avena, Avenula, Brachypodium, Briza, Bromus, Calamagrostis, Dactylis, Desmazeria, Digitaria, Echinochloa, Eleusine, Elymus, Festuca, Gaudinia, Glyceria, Holcus, Hordeum, Lagurus, Lolium, Panicum, Phalaris, Phleum, Phragmites, Poa, Secale, Setaria, Triticum, ? Polygonum, ? Potamogeton, Veronica, ? Typha and Verbena elsewhere. Widespread in England. Also recorded in the Republic of Ireland. Widespread in the Palaearctic region. Also recorded from Nearctic and Australasian Regions.

Hydrellia griseola (Fallén, 1813) [Diptera: Ephydridae].

Key for the identification of the known mines of British
non-Diptera 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 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 > Leaf-miner and case-bearer: The larva lives outside the mine, protected by a case, and feeds on the underlying plant tissues via a hole cut in the epidermis. From that point it eats away as much leaf tissue as it can reach without fully entering the mine. Mine does not contain frass (Coleophora species)

2

1b > Leaf-miner, but not a case-bearer: The larva lives mainly inside the mine. Mine usually contains frass. In later instars the larva may live sandwiched between two more or less circular sections cut from the leaf.

3

2a > 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°. The case is illustrated in British Leafminers.

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].

2b > Seed-feeder, leaf-miner and case-bearer: Initially it feeds on the seeds of thyme and then uses the seedhead as a case. It overwinters in this case and starts feeding again in March on grass spp. It then makes a case from the mined blade of grass. The larva initially feeds on the seeds of thyme, feeding within a floret and using this as its case. After overwintering, it changes foodplants to grass, and eventually forms an elongated case from two grass blade portions sewn together. The larva begins its life by eating out the ripe fruit of a thyme floret. The emptied and dried calyx functions as its first case, in which it hibernates. After hibernation the larva switches to grasses, initially in its original thyme case. Later a new case is made out of a mined grass leaf. This final case is about 11 mm long, two-valved, straw-coloured, has a mouth angle of 25°, and bears a striking resemblance to a grass spikelet.

On Thymus and the grasses Anthoxanthum odoratum, Briza media, Dactylis glomerata, Holcus lanata and Poa annua in Britain and these grasses plus Alopecurus pratensis, Avenula pubescens, Bromus hordaceus, Elymus and Koeleria elsewhere. Widespread in Britain and continental Europe. Also recorded in the Republic of Ireland.

Coleophora lixella Zeller, 1849 [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. 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.

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.

On 'various grasses', but not yet on Holcus, in Britain plus Luzula, Agrostis, Arrhenatherum, Brachypodium, 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

On Dactylis glomerata, but not yet on Holcus, in Britain. 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.

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].

3e > 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.

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].

3f > Leaf-miner: The larva mines downwards and forms an irregular mine with a silken tube in the centre, which is mixed with frass. Mine transparent (therefore conspicuous), generally descending from the leaf tip. Over the entire length of the mine stretches a central silken tube, in which the larva can retreat and can move quickly up or down. The tube also contains the frass. The larva feeds laterally from the tube, which makes the sides of the mine very irregular.

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].

3g > 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.

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. 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.

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. 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.

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.

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.

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.

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