The leaf and stem mines of British flies and other insects
 

(Coleoptera, Diptera, Hymenoptera and Lepidoptera)

by Brian Pitkin, Willem Ellis, Colin Plant and Rob Edmunds

 

CORNUS. Dogwoods and Dwarf Cornel. [Cornaceae]


Two native species of Cornus are recorded in Britain - Dwarf Cornel (C. suecica) and Dogwood (C. sanguinea). Eight other species have been introduced, including Cornelian-cherry (C. mas), White Dogwood (C. alba), Red-osier Dogwood (C. sericea) and Creeping Dogwood (C. canadensis).

Eight British miners are recorded on Cornus.

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



Key for the identification of the known mines of British
insects (Diptera and non-Diptera) recorded on Cornus


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: Lobe case. The full grown case is about 7 mm long. The mouth angle is 0°, causing the case to lie flat on the leaf. The case is gradually enlarged by the addition of rings that are cut out of the epidermis. The rings become gradually larger, and stick irregularly out of the contour of the case. The rings are cut out of the lower epidermis of the mine. This implies that mines may have both normal, small openings, and large ones. Compare for instance C. violacea, that cuts rings out of the upper epidermis. The larva feeds briefly initially and again after over wintering. It then aestivates until Autumn. It makes one case which it enlarges by adding pieces of excised lower epidermis .

On Cornus, Frangula, Lonicera, Rhamnus, Symphoricarpos and Viburnum in Britain and Cornus, Frangula, Lonicera, Rhamnus, Swida, Symphoricarpos and Viburnum elsewhere. Southern England. Widespread in continental Europe.

Coleophora ahenella Heinemann, 1877 [Lepidoptera: Coleophoridae].

2b > Leaf-miner and case-bearer: The early case is tiny and the larva makes a series of tiny holes on the leaf. After overwintering it makes a shiny pistol shaped case in spring and window feeds . The young larva, before hibernation, makes tiny mines, sometimes tens in one leaf. After hibernation window feeding is done. In this latter stage the larva lives in a shining black pistol case of about 7 mm, that, with a mouth angle of 70°-80°, stands almost perpendicular on the leaf.

On Crataegus, Malus, Prunus, Pyrus and Sorbus, but not yet on Cornus, in Britain plus numerous genera and species of several plant families, including Cornus, elsewhere. Occurs in England and Wales, commoner in the south. Widespread in continental Europe.

Coleophora anatipenella (Hübner, 1796) [Lepidoptera: Bucculatricidae].

2c > Leaf-miner and case-bearer: The larva feeds on a wide range of trees, shrubs and herbs, favouring Rosaceae, but not exclusively. The fully developed cased larva may be found active in October and again, after winter diapause, in April. Cases, about 6 mm, of diapausing larvae may be found through winter, fixed to a tree or fence post. The dorsal surface of the case is usually covered in leaf fragments, but they can sometimes be worn off almost smooth. The ventral surface is swollen at the middle and has a keel, which usually bends upwards at the posterior. The cases of C. ahenella (on Rhamnus, Frangula, Viburnum and Cornus) and C. potentillae (case less swollen, keel not bent up, resting position less prone) are very similar. Brownish lobe case that lies almost flat on the leaf, either on the upper or on the lower side. Case widest about the middle. Ventrally there is a distinct keel. Mouth angle 0°. Full depth mines rather large. The flaps of cuticular tissue that serve to enlarge the case are cut out of the upper epidermis. (contrary to C. ahenella and C. potentillae, that use tissue from the lower epidermis). The removal of these tissue flaps creates holes that are much larger than those that serve as the entrance to the mine.

Coleophora violacea larva,  lateral
Coleophora violacea larva, lateral
Image: © Willem Ellis (Bladmineerders van Europa)

Polyphagous. On numerous genera and species in several plant families, but not yet on Cornus, in Britain. On numerous genera and species in several plant families, including Cornus elsewhere. Widespread in Britain and continental Europe.

Coleophora violacea (Ström, 1783) [Lepidoptera: Coleophoridae].

3a > Leaf-miner: A gallery leads to blotch, with oval cut-out 5.5-7 mm long. There are two or three brown specks at start of mine (trial slits made by ovipositor) . The combination of mine and cut-out is very distinctive. Initially a short corridor close to the leaf margin, suddenly widening into a large blotch, that often overruns the corridor. Finally the larva makes an oval excision of 5.5-7 mm long, and drops with it to the ground. In this excision, that now functions as a case, the larva continues living free. Before the onset of winter, pupation takes place within the case. The female makes a number of test punctures, that often can be seen as a curving row of 2-7 brown spots perpendular to the initial corridor.

On Cornus in Britain and elsewhere. Throughout most of England. Widespread in continental Europe.

Antispila metallella (Denis & Schiffermüller, 1775) [Lepidoptera: Heliozelidae].

3b > Leaf-miner: The initial mine is a short gallery at the leaf edge, which expands to from a blotch. The larva cuts out an oval case 4-5.5 mm long (British leafminers), in which it subsequently lives amongst leaf litter on the ground.

Oviposition usually close to the leaf margin. From there starts a corridor of about 1 cm; it contains much frass, is often somehat tortuous in its beginning and as a roll closely follows the leaf margin. After a moult the direction reverses and the larva starts making a full depth blotch that can become several cm long and wide. Here the frass lies in scattered grains. The full grown larva covers an oval section at the margin of the blotch with a light brown pergamon-like layer of silk, cuts this loose and drops within it to the ground. The excision that is made is about 4-4.5 mm long. Unlike A. metallella the female does not makes test punctures before ovipsition.

On Cornus mas in Britain and elsewhere. Occurs locally in parts of southern England. Widespread in continental Europe. Recently van Nieukerken et al. published a paper separating Antispila petryi (on Cornus sanguinea) and A. treitschkiella (on Cornus mas) (see Nota Lepidopterologica 41 (1): 39-86. A. treitschkiella is a recent invader now spreading in England.

Antispila treitschkiella (Fischer von Röslerstamm, 1843) [Lepidoptera: Heliozelidae].

3c > Leaf-miner: Oviposition by way of an ovipositor, no egg visible therefore. The larva makes an irregular blotch. The part of the mine nearest to the oviposition site is more thranslucent than the later, in transparancy more greenish, part of the mine. The mine usually lies close to the leaf tip, often several together. After its first moult the larva makes a roundish excision, 3-4 mm in diameter. Incurvaria larvae, while resting, take a horse-shoe like posture, unlike the larvae of Antispila species. Sandwiched herein it drops to the ground and continues feeding of dead leaves. The excision occupies about half of the surface of the blotch.

On Vaccinium myrtillus, Prunus and Rubus chamaemorus, but not yet on Cornus, in Britain. On several genera and species of several plant families, including Cornus, elsewhere. Widespread in much of the British Isles and continental Europe.

Incurvaria oehlmanniella (Hübner, 1796) [Lepidoptera: Incurvariidae].

3d > Leaf-miner: The larva starts making a corridor of a few mm, followed, and mostly overrun, by a circular blotch of 4-5 mm diameter. Generally several larvae feed in a single leaf, creating a distinctive pattern of feeding windows. The larvae then cut out circular cases and drop to the leaf-litter to continue feeding, leaving behind a leaf containing many circular or oval cut-outs.

On Alnus, Betula, Carpinus, Corylus, Malus and Tilia, but not yet on Cornus, in Britain and Acer, Alnus, Betula, Carpinus, Corylus, Ostrya, Cornus, Robinia, Malus, Prunus, Pyrus and Sorbus elsewhere. Widely distributed in Britain and continental Europe.

Incurvaria pectinea Haworth, 1828 [Lepidoptera: Incurvariidae].

3e > Leaf miner: A long, narrow, upper surface mine widening at the end and with frass in conspicuous black strips. Pupation normally takes place on the ground but the puparium not infrequently remains in the exit slit at the end of the mine (Spencer, 1976: 370, 371 (fig. 645)).

Upper surface corridor from start to end. The frass liquifies partly, forming a a broad dark-brown central band. Pupation mostly outsaide the mine, but the puparium may often be found within. In that case often an untidy exit slit has been formed; the anterior spiracles do not penetrate the epidermis.

A long upper surface gallery. Frass broad, linear, conspicuous and black .

On Cornus in Britain and elsewhere. Probably widespread in Britain. Widespread in continental Europe

Phytomyza agromyzina Meigen [Diptera: Agromyzidae].



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