The identification of leaf-mining lepidoptera introduction
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| THE IDENTIFICATION OF LEAF-MINING LEPIDOPTERA
INTRODUCTION The aim of this booklet is to enable the user to identify most of the leaf-mining lepidoptera. It is not possible to cover all the leaf-mining species in such a small booklet, however over 90% of the true mining species should be identifiable with its use. The guide has been kept as simple as possible. Along with the usual keys I have added a chart on hawthorn to assist with the identification of the Nepticulidae. Much of the information contained herein is gleaned from volumes 1 and 2 of “The Moths and Butterflies of Great Britain and Ireland” with some addition notes supplied by A. Maitland Emmet along with the occasional modification of my own. I have also included within the birch feeding miners a key written by David Manning on the Eriocraniidae. A word of warning before you start to look at mines, some flies, beetles, wasps and sawflies also produce larvae that mine leaves, so it is possible that these could be mistaken for lepidopterous mines. A good guide is that the larvae of the Nepticulidae usually leave their frass, droppings, in a continuous line and the larvae of the Gracillariidae usually pile their frass in a particular place inside the mine; there are, of course, a few exceptions to this. Generally flies etc. leave their frass in irregular patches and usually there is much less frass in the mines of flies etc. than in those produced by lepidoptera. A further guide is to look at the list of foodplants which follows, if the plant you have found a mine in is not in this list it is quite likely that it will not be a lepidopteran mine. Once you have found a mine the next stage is to decide which family it belongs to. The Nepticulidae (Ectoedemias and Stigmellas) are the largest group of true miners, making a tunnel in the leaf in which all the parenchyma is consumed leaving behind the larva a trail of frass. The mines of the Ectoedemias often start with an irregular mine in close proximity to the egg; the mine then becomes a tunnel, which often leads to a blotch mine. Tenanted Ectoedemia mines can be found in fallen leaves as late as November. The Stigmellas usually mine tunnel fashion away from the egg, sometimes leading to a blotch or false blotch. The Gracillariidae (Caloptilias, Parornix and Phyllonorycters) either fold over a leaf edge, make a ‘blister’ on the surface of the leaf or consume the parenchyma making a blotch. All the Gracillariidae feed on sap until the third instar and are virtually impossible to identify at this early stage. The Parornix finish their feeding under a folded leaf edge with the exception of P. anglicella, which makes a cone. The Phyllonorycters form a blotch on the surface of the leaf and all species pupate inside the blotch. It is possible to identify Phyllonorycters by microscopic examination of the pupal case. The Tischeriidae make a blotch mine on top of the leaf, which is lined with silk. The way the silk is placed in the mine depends on the species, but it is used by the larva as an aid to facilitate movement within the mine. They also make a slit in the upper epidermis through which they eject their frass. The Heliozelidae and the Antispila feed as miners and then cut an oval hole from the blade of the leaf, which is used to construct a cocoon. The Bucculatrix start feeding as leaf-miners, and then most species leave the mine as they develop to feed externally. While feeding externally the larva eats out small windows in the leaf, generally from below, leaving the upper epidermis intact. The Eriocraniidae mine in the spring from May to July eating out large areas of the parenchyma of their host leaf leaving long strings of frass in the mine making them easily distinguishable from the mines of other species. I have included the Momphidae that feed on Enchanter’s Nightshade and Rock-rose, but have not found it possible to write a simple key for those species that feed on Willowherbs, so I refer the reader to the literature for those species. A few members of the following families are also included, Incurvariidae, Lyonetiidae and Yponomeutidae. However, many members of these families are not miners. There are a few other species of lepidoptera that do mine leaves that are not covered in this booklet. Many of these only mine for the first instar before they start to feed externally, so most of them should present no problem as they are unlikely to be confused with the true miners. There is a moth that is very common and whose mines can be confused with those of the Nepticulidae by the inexperienced. This is Lyonetia clerkella, which mines many different plants. The commonest being members of the Rosaceae, but it can also be found on birch, hawthorn and apple. However, the mine can be readily distinguished from that of a Nepticulidae by the following points. Firstly the egg is laid inside the leaf, as the female pierces the lower epidermis before laying, whereas the female Nepticulidae lay their eggs on the surface of the leaf. Secondly, the mine is very long, often spreading over most of the leaf in any direction, whereas the Nepticulidae have relatively short mines, which often follow a set pattern. The numbers which follow the description in the key and are in square brackets [ ] refer to the months when the mines should be occupied by larva. (e.g. [7+9-10] refers to July and September to October, showing that this species is bivoltine). There may be some variation in this depending on the season and which part of Britain the mines are found. The numbers following the names of the moths are the British Log Book numbers as recorded by J.D. Bradley and D.S. Fletcher in 1979; and are there to make cross-references to other works easier. The nomenclature follows Bradley 2000 with additions as published in the entomological journals. There have been quite a number of changes since Bradley and Fletcher was published in 1979. Several species have been synonymised with other species and others have been deleted because of misidentification. Others have undergone name changes, so be aware that if you compare the following with previous lists there may be discrepancies. Barry Dickerson September 2007 IDENTIFICATION OF LEAF-MINING LEPIDOPTERA FOODPLANTS
AGRIMONY Nepticulidae Mine gallery throughout frass with clear margins [5-6+7-8+10-3] ….Stigmella aurella 50 Mine gallery leading to blotch, pupa in mine [8-11] …...…….Ectoedemia agrimoniae 26 Mine gallery leading to blotch, pupa external [7+9-11] ..…...Stigmella aeneofasciella 55 ALDER Nepticulidae Mine in buds or twig bark [?-5] ………………….…….Bohemannia quadrimaculella 19 Mine a gallery in the leaves with linear frass filling only one third of mine [7+9-10] …… ………………………………………………………………..….. Stigmella alnetella 115 Mine a gallery in the leaves frass dispersed or linear, filling two thirds of the mine; larvae with dark prothoracic plate [7+9-10] …………………...Stigmella glutinosae 114
HeliozelidaeMine in midrib, inconspicuous, then into a lateral vein and across leaf back into midrib finally cutting out a hole in leaf blade approximately 5 x 3mm [6-9] ……………………. ……………………………………………………....…...…….Heliozela resplendella 156 Bucculatricidae Mine long, narrow almost filled with black linear frass beside a vein, later the larvae leaves the mine from upperside and eats out windows from the underside of the leaf [8-9] …………………..………………………….….…………..Bucculatrix cidarella 272 N.B. early mine can be confused with that of a Nepticulidae, but egg matt black and rough in appearance. Gracillariidae 1 Mine on upperside of leaf………………………………………….……………..………2 Mine on underside of leaf………………………………………….……………………..3
Mine subcircular with strong central crease, but remaining flat, cuticle pale green, sometimes discoloured brown, not flecked with brown frass [7+9-10] ……………….…. ………………..……………………………….…………. Phyllonorycter stettinensis 357 (N.B. mines that do not have cease are hymenopterous)
in folded leaf-edge [7-8] ……..………………….……….. Caloptilia falconipennella 289 Mine usually away from leaf-margin and more than 10mm long; lower cuticle green; larvae mine throughout …………..………………………..…………………………….4 4 Mine very large, extending from midrib almost to leaf margin; larva grey; pupa in a cocoon without frass in centre of mine [9-10] .…….……Phyllonorycter froelichiella 358 Mine smaller, not exceeding 20mm in length; larvae whitish………………..…………..5
Pupae in a cocoon not edged with frass………………….……………………………….6 6 Always on Grey Alder; pupa usually in middle of mine [7+9-10] ……………………….. ……………………………………………………………..Phyllonorycter strigulaella 344 Usually on other Alder species; pupa usually at one end of mine, larva with pale yellowish tinge [9-10] …………………..………….….. Phyllonorycter kleemannella 360 ALDER BUCKTHORN Bucculatricidae Mine starts as a tightly wound spiral staining leaf blackish violet; then the mine straightens with no staining; after leaving mine larva eats out windows from below [8-9] ……..…………………………….………………………..…..Bucculatrix frangulella 270 APPLENepticulidae 1 Mine terminating in a blotch ……………………………………….……..……..………2 Mine forming a gallery throughout, though sometimes ending in a false blotch …….….4 2 Blotch small, generally in an angle of veins; larva yellow [6-7+10-11] ………………… …………………………………………………………..………Stigmella incognitella 78 Blotch larger, generally on leaf margin …………………………….……………………3 3 Blotch usually aborbing earlier gallery; frass black and linear; larva yellow feeding in June and July, exit hole on underside [6-7] …..….….….…..Bohemannia pulverosella 40 Gallery usually along leaf-margin; frass brown, dispersed; larva greenish white with dark head and ventral spots (mines venter upwards); feeding late August to early October; exit hole on upperside [8-10] …………………….…...Ectoedemia atricollis 29 4 Frass, except at beginning of mine, dispersed; larva green feeding in September and October [9-10] .………………………………………….…..Stigmella oxyacanthella 100 Frass linear throughout mine …………………………….…..…………………………..5 5 Early mine more contorted; later gallery often with hairpin bends resulting in false blotches; larva green and often gregarious [8-10] ……….…... Stigmella desperatella 105 Early mine less contorted; gallery widening considerably, but seldom forming a false blotch larva yellow and not gregarious [6-7+9-10] …….…………...Stigmella malella 97 |