Leaf Mines

With fewer and fewer adult moths left to see now this year, just a reminder that we're fast approaching peak "leaf-mine season".  This is an excellent route to increasing knowledge of the species in your garden because mines are the easiest way to identify some of our smallest moths which might not otherwise get recorded.

Dwarfed by the huge willow behind it, in our front garden there is small Norway Maple Acer platanoides which is probably about 25 years old.  I know of no others in the immediate area yet it is home to Ectoedemia sericopeza and Phyllonorycter joannisi (both specific to that variety of Maple) as well as Stigmella aceris (also found on Field Maple Acer campestris) and several Caloptilia species (found on other Acer varieties too).  A brief look at the tree this afternoon very quickly produced mines of Phyllonorycter joannisi and Stigmella aceris. 

Norway Maple, Westcott 25th August

Mine of Stigmella aceris, Westcott 25th August

Mine of Phyllonorycter joannisi, Westcott 25th August

The Stigmella aceris larva had clearly been parasitized and you can see the black wasp pupa still inside the left-hand end of the corridor mine.  The tentiform mine of Phyllonorycter joannisi was found on the underside of a leaf and still had an active larva inside.

There is plenty of help available on-line and a good place to start is the British Leaf-mines web-site which is third in the list of Links in the right hand column on this page.  It is, of course, essential that you can correctly identify the tree or plant species on which you find a mine.  Thereafter, in many cases the time of year, type of mine, position of the egg, frass pattern and shape and colour of the larva itself all contribute to getting an ID to species and all you really need is a small hand lens and a camera (in the case of corridor mines like the Stigmella above, it is often easier to see much of the required detail by taking a back-lit photo and then viewing it on a computer screen). 

Dave Wilton
Westcott, Bucks