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 |