| An introduction to leaf-mines |
| Leaf mines
are characteristic galleries created on both the upper
and lower surfaces of leaves. Most mines are created by
feeding lepidoptera larva, but others are the result of
beetle, fly and sawfly larval stages. Only lepidopterous
mines will be dealt with here. The study and identification of leaf mines, usually results from an earlier interest in the larger (macro) moths. Moth trapping invariably attracts a range of smaller (micro) moths and once entering into their identification, the interest in leaf mines usually develops. This certainly happened in my case. If I was to be serious about recording the moths of the Eakring and Kersall area, then that should include all species. |
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Left: An
occupied Stigmella glutinosae leaf mine, photographed on Alder (Alnus
sp) at Warsop Main Pit Top in early November 2006.
This type of leaf mine is a gallery mine, with linear
frass throughout it's length. The inset shows the larva in close up, with the head to the right. The dark line down the centre of the larva is the gut. |
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| Leaf mines
can be categorised into two types - gallery mines and
blotch mines. Both types offer self explanatory
descriptions, but not all mines are visible on the leaf's
upper surface, although there is usually some faint
indication of a mine being present. The way the frass is
deposited by the larva during the mine's construction is
frequently a good indicator towards identification. There are two main types of frass dispersal - linear (a line of frass following the centre of the developing mine) or dispersed (the frass spread evenly or unevenly within the mine) Leaf mines are created by the larva eating the leaf, between the upper and lower surfaces. The resulting mine is frequently obvious to the eye, even though all leaf mines are generally small. |
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Gallery mines Species that construct similar gallery mines and share the same foodplant, can sometimes be seperated by the method of frass dispersal. Even if frass dispersal is linear, the width of the frass in relation to the width of the gallery can clinch an ID. Gallery mines vary considerably, with some species constructing more contorted galleries than others. The larvae of some leaf miners often construct a gallery mine initially, which eventually becomes a blotch mine. The example shown is Stigmella tityrella, a gallery-type mine commonly found on Beech (Fagus sp) | |
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Blotch mines These mines again show considerable variation in size and shape. Frass within blotch mines is often dispersed unevenly, but some of of the Eriocraniidae produce distinctive "arcs" of frass, which aids identification. The blotch mine in the left-hand photograph is that of Phyllonorycter coryli, which can be found commonly wherever Hazel (Corylus avellana) grows. | |
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Blotch mines produced by the Coleophoridae group are more unusual in that the larva feeds inside the leaf, but constructs a protective case and lives externally either above or under the leaf. Many larval cases are distinctive enough to enable an accurate species ID in the field, but identification of the adult moths is often only possible by genitalia examination through a microscope. | |
| Leaf mining insect groups | ||||||||||||||
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