mine key

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
October 2007