Forest Pests: Insects, Diseases & Other Damage Agents

Csóka, György (2003): Levélaknák és levélaknázók - Leaf mines and leaf miners. Hungarian Forest Research Institute. Erdészeti Turományos Intézet, Agroinform Kiadó, Budapest, 192 pp.

The leaf mine can be considered as an imprint of the leaf miner's feeding habits and can serve as a "call card". The leaf mines vary a lot in shape and size, therefore they can be classified on many different ways. One of the easiest and most evident ways is to classify them based on the shape of the mine.

The eleongated bending mines are usually called "serpentine" mines. These are made when the larva advances into one direction during its feeding. The width, length and the widening rate of the serpentine mine are usually typical for the species and can help in the identification. The location of the mine (leaf margin, inside the leaf) is also imoportant character. While females of some species lay eggs on the leaf margins others do in the middle of the leaf blade, so the mine begins respectively. The serpentine mines often follow the weins, an in some cases it is coiled in a spiral line (see Stigmella prunetorum on page ).

Blotch mine is made when the larva turns around itself during its feeding. So the width and length of the mine is not as different as in case of serpentine mines. The shape of blotch mine can either be totally irregular or quite regular (i.e. circle, oval). Many species of lithocolletid leaf miners (family Lithocolletidae) make typical oval blotch mine. Other species (i.e. Parectopa robiniella - page) makes irregularly forking "amoeba-like" blotch mines.

Many mines are combination of these two basic types. They begin as serpentine mine and later become blotch mine. This change can either be gradual or sudden. The larger blotch mine often incorporates the smaller serpentine mine, so it becomes invisible.

It is important character whether the mine found on the upper surface or the backside of the leaf. Often happens that the mine begins on the backside and the larva bores itself through to the upper surface. In the upper side mine the larva feeds closer to the upper epidermis (Fig. 1), in the backside mine closer to the lower epidermis.

In case of bilateral mines (Fig. 2) the larva consumes most of the tissues between the upper and lower epidermis, leaving a very thin layer of skin on both side. These mines are often window-like transparent. The location of the mines (upper side versus back side) is characteristic for species, although some species can make mines on both sides.

Fig. 1.: Dissection of a mine on the upper surface (after Hering)

Fig. 2.: Dissection of a bilateral mine (after Hering)

Some mines pull the leaf tissues together forming a tent-like bump on the opposite side. Mines of some species are hardly visible, because of this deformation.

The presence, location, way of deposition and colour of faeces all are important information for leaf miner species. Some species drop its faeces out of the mine via small holes on the mine. (i.e. Parectopa robiniella), other species regularly remove the faeces from the mine. However the faeces can be found within mines of many species. In serpentine mines of pigmy moths (family Nepticulidae) the faeces is regularly deposited in the middle line of the mine. It usually fills up totally the first part of the mine, but later faeces free bands may be seen on both sides. For some species the faeces is deposited in short bends (see Stigmella aceris on page). In mines of agromyzid flies (family Agromyzidae) the faeces is sometimes deposited in dotted lines, not rarely on both sides of the mine.

The presence, location, way of deposition and colour of faeces all are important information for leaf miner species. Some species drop its faeces out of the mine via small holes on the mine. (i.e. Parectopa robiniella), other species regularly remove the faeces from the mine. However the faeces can be found within mines of many species. In serpentine mines of pigmy moths (family Nepticulidae) the faeces is regularly deposited in the middle line of the mine. It usually fills up totally the first part of the mine, but later faeces free bands may be seen on both sides. For some species the faeces is deposited in short bends (see Stigmella aceris on page). In mines of agromyzid flies (family Agromyzidae) the faeces is sometimes deposited in dotted lines, not rarely on both sides of the mine.

In the blotch mines faeces can be found scattered, or deposited in smaller or larger lumps. In some cases the faces is concentrated in the middle of the mine (see Stigmella plagicolella on page).

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