The Importance of Recording Leaf-mines

     Many of our smallest micro-moth species are significantly under-recorded as adults because of the difficulties of indentifying them at that stage.  However, because their larvae are often restricted to a single food-plant, if you know your trees and shrubs well enough you should be able to identify most from the mines within which those larvae live.  Searching out mined leaves is surprisingly easy at the correct time of year and can be done anywhere.  It can also become quite an addictive pastime!   Your garden can be a good place to start, giving a boost to the garden moth-list and providing very useful records of some otherwise difficult species.  Features such as the position on the leaf of the egg, the shape of the mine, the colour and pattern of the larval frass and the colour and shape of the larva itself all combine to give an accurate identity in most cases.  The only equipment needed is a x10 hand lens and a camera (for corridor mines a back-lit picture of the leaf is often essential to see all of the detail).  There is plenty of help available on-line, for example here, here and here, and there is also a public Facebook group dedicated to the subject ('British leafminers').

Corridor mine of Stigmella anomalella on dog rose

Blotch mines & leaf-edge folds of Parornix devoniella on hazel

Thinking that 2016 would end up being a poor one for micros in the garden at Westcott, I made a particular effort to look for mines here between September and November this year as the moth trap started winding down towards winter.  A bit of judicious hedgerow planning in bygone years has ensured that we have a good mix of native plant species available and 41 micro species were recorded as mines, of which the adult was seen in only 9 of them (most requiring dissection to confirm).  The tiny Nepticulids (the Ectoedemia and Stigmella species) seem particularly reluctant to come to light and on the rare occasion when I do manage to capture an adult it often turns out to be female and they are very difficult if not impossible to identify via dissection anyway!  The table below lists those found in the garden as mines in 2016, the columns giving species name, the date on which the mine was found, the food-plant, whether or not the mine was tenanted and finally the date on which an adult was recorded (if at all):

Stigmella aurella	25 April	Bramble	Vacated
Stigmella lemniscella	28 September	Elm	Active
Stigmella plagicolella	21 August	Blackthorn	Vacated
Stigmella salicis	31 October	Goat Willow	Active
Stigmella obliquella	3 October	Willow	Active	Adult 22 August
Stigmella ulmivora	30 August	Elm	Vacated
Stigmella anomalella	12 October	Dog Rose	Active
Stigmella viscerella	3 October	Elm	Active
Stigmella hybnerella	1 September	Hawthorn	Vacated
Stigmella oxyacanthella	26 September	Rowan	Active
Stigmella aceris	2 November	Norway Maple	Vacated
Stigmella regiella	26 September	Hawthorn	Active
Stigmella microtheriella	12 September	Hornbeam	Active
Stigmella luteella	2 November	Birch	Active
Stigmella lapponica	25 June	Birch	Active
Leucoptera malifoliella	2 September	Apple	Vacated
Lyonetia clerkella	2 September	Blackthorn	Active	Adult 15 June
Bucculatrix albedinella	30 August	Elm	Vacated
Bucculatrix thoracella	7 October	Lime	Vacated
Bucculatrix bechsteinella	28 September	Hawthorn	Vacated	Adult 10 June
Caloptilia rufipennella	2 September	Sycamore	Vacated
Caloptilia syringella	2 November	Lilac	Vacated
Parornix anglicella	12 September	Hawthorn	Vacated	Adult 27 July
Parornix devoniella	20 September	Hazel	Active
Parornix finitimella	2 September	Blackthorn	Active	Adult 13 June
Phyllonorycter messaniella	2 September	Apple	Vacated
Phyllonorycter oxyacanthae	12 September	Hawthorn	Active
Phyllonorycter spinicolella	2 September	Blackthorn	Active	Adult 31 August
Phyllonorycter cerasicolella	27 September	Cherry	Active
Phyllonorycter corylifoliella	1 September	Hawthorn	Vacated	Adult 8 August
Phyllonorycter leucographella	25 April	Firethorn	Vacated	Adult 31 August
Phyllonorycter viminiella	3 October	Willow	Vacated
Phyllonorycter coryli	9 September	Hazel	Active
Phyllonorycter schreberella	30 August	Elm	Active
Phyllonorycter ulmifoliella	2 November	Birch	Vacated
Phyllonorycter emberizaepenella	10 October	Snowberry	Active
Phyllonorycter tristrigella	30 August	Elm	Active
Phyllonorycter nicellii	5 October	Hazel	Active
Phyllonorycter joannisi	28 September	Norway Maple	Active
Phyllonorycter geniculella	10 October	Sycamore	Vacated
Phyllocnistis saligna	9 August	Willow	Active	Adult 14 June

Lyonetia clerkella is probably one of the most common leaf-miners there is and it actually uses a number of different food-plant species in the garden, being recorded here on apple, birch, cherry and hawthorn as well as blackthorn, but its random corridor mine is quite distinctive, as is the larva if present. 

Mine of Lyonetia clerkella on hawthorn

Distinctive larva of Lyonetia clerkella

Adult Lyonetia clerkella (dark form), wing length 4mm

While vacated mines of many species can easily be identified, in some cases finding a tenanted mine is a necessity because the larvae provide additional clues as to the species involved. 

There are further 13 micro-moths for which the food-plant is present in the garden and on which mines have been recorded here previously but they weren't noticed this particular year.  Amongst them were five species recorded as adults during 2016 so they at least are presumably still present:
 

Ectoedemia intimella		Willow
Ectoedemia occultella		Birch
Stigmella floslactella		Hornbeam
Stigmella tiliae		Lime
Stigmella sakhalinella		Birch
Leucoptera laburnella		Laburnum		Adult 11 July
Bucculatrix demaryella		Birch
Caloptilia stigmatella		Willow		Adult 15 July
Caloptilia semifascia		Norway Maple		Adult 5 September
Phyllonorycter blancardella		Apple		Adult 22 July
Phyllonorycter hostis		Quince
Phyllonorycter salicicolella		Goat Willow		Adult 21 July
Phyllonorycter trifasciella		Honeysuckle

Furthermore, several other species have been recorded in the garden but for which the food-plant is not present although it can be found in the general neighbourhood.  The five below were seen during 2016:

Bucculatrix nigricomella		Ox-eye Daisy		Adult 22 July
Bucculatrix ulmella		Oak		Adult 7 June
Aspilapterix tringipennella		Plantain		Adult 4 August
Phyllonorycter harrisella		Oak		Adult 22 July
Cameraria ohridella		Horse Chestnut		Adult 22 August

So despite their tiny size some of these moths are able to travel a fair distance.  Phyllonorycter platani has been recorded in the garden and the only host tree in the village (London Plane) is a good 400 metres away.

Another source of potential additional moths for anyone's garden list are the Coleophora species whose larvae mine leaves from within a case made out of vegetable materiel, but these require a lot more effort to identify and I haven't really looked all that carefully for them, preferring instead to rely on dissection of adults (40 different species have been recorded in the garden).