Upper- of lower-surface

Mines that are visible only at the upper or lower surface of a leaf are, exceptions apart, either tentiform mines, or mines made by larvae of the fly family Agromyzidae.

upper-surface

In upper-surface mines the palissade parenchyma has been eaten away. Because of the whitish upperside they are easy to find.

12532

Phytomyza minuscula on Lesser Meadow Rue: upper-surface mine

lower-surface mine

Under-surface mines, in which only the the sponge parenchyma is eaten away, are less easy to find, especially when the lower surface of the leaf is hairy. This type is much rarer than upper-surface mines – possilby because the sponge parenchyma is less nutritious than the palissade parenchyma.

7196

Aulagromyza tridentata on White Willow: lower-surface mine

alternating

An odd agromyzid species starts by making an upper-surface mine, to continue it at the lower surface. Many more species start at the leaf under side, and continue with an upper-surface mine. Generally the lower-side part of the mine is a very shallow corridor, quite difficult to observe (the more so in herbarium material).

Liriomyza strigata mine (part)

Liriomyza strigata on Sow-thistle: under-surface part of the corridor

interparenchymatous mine

In a few species the mine is made on the interface of palissade and sponge parenchyma, which gives this type of mine a characteristic yellow-green appearance. They are called interparenchymatous mines.

Phytomyza spinaciae mine

Phytomyza spinaciae on Creeping Thistle: interparenchymatous mine


transverse section

Phytomyza spinaciae on Creeping Thistle: transverse section

perforate mines

Another rare type of agromyzid mines. It concerns an interparenchymatous mine, from which numerous holes are eaten in the “roof”, i.e. the palissade parenchyma. When hold against the light the mines looks riddled. In the field the mine looks most like a patch diseased by some fungus.

8278

Phytomyza heracleana on Hogweed: perforate mine, seen in transparancy

epidermal mines

Larvae of the moth genus Phyllocnistis make long corridor mines, entirely in the epidermis of the leaf (sometimes also of the petiole and bark of young twigs). The epidermis is colourless (contains no chlorplasts) and the rather broad, silvery corridors strongly resemble snail trails. Phyllocnistis-larvae drink, rather than feed, on cell sap; this makes the frass almost invisible, a dark, ill-defined continuous line at most.

The genus Phyllocnistis belongs to the family Gracillariidae. In other genera of this family the larvae also begin their life as cell sap drinkers in an epidermal corridor, but after some moults they switch to the consumption of parenchyma, and the formation of a tentiform mine.

7289

Phyllocnistis xenia on Abele: epidermal mine

29/04/2011

mod 27.vii.2017