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The identification of 'problem' species:
1. Oak Nepticulidae:

In the 'Microlepidoptera Review of 2002' in The Entomologists Record (Nov,2003), John Langmaid and Mark Young said that new records for this Review, of the following Stigmella species feeding on Oak (Quercus), would no longer be accepted unless the mines were tenanted and the moths bred through. They were following the advice of Erik van Nieukerken. The species were S.atricapitella, S.ruficapitella, S.roborella, S.samiatella and S.svenssoni.

John has kindly amplified his thoughts for this newsletter saying that 'The real problems are between atricapitella and roborella. I have several times bred roborella from mines with quite a thick line of frass, but never have I bred atricapitella from a mine with a very narrow thin frass line. According to van Nieukerken, the egg can be on either side of the leaf with these two, but I have always found the egg to be on the underside with both species. However, if Erik says that he must have evidence, so I suppose we oughtn't to accept diagnoses based on the position of the egg.

Another problem can be between svenssoni and samiatella - Maitland and I always said that the mine starts at right-angles to the vein against which the egg is laid. This could also possibly happen with samiatella, though the mine of that is usually shorter than that of svenssoni - but can vary with the thickness of the leaf. I have found that the egg of samiatella is usually, but not, invariably, on the underside of the leaf, and the configuration of the frass in both species is usually linear to start with, then dispersed for the greater length of the mine, and finally linear again for a variable distance before the end of the mine.

S.ruficapitella has the egg, invariably in my experience, on the upper side, and the frass is usually a thick central line, but I have several vacated
mines with egg on upper side and frass distribution more like samiatella/svenssoni (which is probably what they are).'

He urges people to breed through the moths and KEEP voucher specimens, correctly presented and labelled with date of finding the mine, locality and host plant.

2. Salix Lithocolletinae:

There is a problem in distinguishing between certain Phyllonorycter species on Willow (Salix) and David Manning has drawn our attention to the key ' Die Puppen der mitteleuropäischen Lithocolletinae' by Gregor & Patčoka (2001), where the authors state that there is no difference between the mines or pupae of P.hilarella, dubitella and salicolella. Again, for these species, John's advice holds good - breed them through and keep voucher specimens.

Willem Ellis points out that from Gregor and Patčoka's guide that ' practically all Phyllonorycters can be identified on the basis of the pupa (although you may need a fairly powerful stereo microscope). Even 'stronger' is the combination of the mine characteristics and the pupa. In my view the necessity of breeding really isn't that big'.
 

Black mines on Populus species

 

This mine (upper photo), on Aspen (Populus tremula), found by Bryan Formstone on 27.ix.03 in Gresford, VC50 has prompted some very interesting discussion (which I summarise below). It is unusual as it could have been lepidopterous, hymenopterous or coleopterous!

It has been identified as probably a mine made by a chrysomelid species (Coleoptera) called Zeugophora . There are several species of these and the mines are indistinguishable.

I am very grateful in particular to Willem Ellis and Mark Shaw for their help in this identification and for helpful pointers to the alternatives

Willem says that the mines made by Zeugophora species (Coleoptera) have a characteristic, middle-brown, oviposition mark, like leather, mostly near the margin of the blotch. They also contain  several larvae.

It could have been made by Hetrarthrus ochropoda (Hymenoptera), but the age of the mine is a problem and also, as Willem says 'there is no indication that there is a cocoon in the mine, which is the hallmark of Heterarthrus'. Mark indicates that H. ochropoda usually starts on the leaf edge.

There is yet another possibility - Leucoptera sinuella (Lepidoptera) - but this species is of uncertain status in the UK (known only from Scotland), although it does make black blotches on Populus. It is a miner found in the Netherlands and France though, as Mark points out ' usually in large suckering leaves of Populus nigra-group. The mine is large, semi or very gregarious, and I think (not sure, however) always adjoins leaf edge, and always on a leaf ex rapidly growing shoot - your leaf isn't the right kind of leaf.' Willem says that ' the real distinguishing character of this species is the presence of one or two groups of glistening empty egg shells at the upper side of the mine; mostly they are on a line, along a lesser vein. Each of them is about the size of a Stigmella egg, and therefore not easily visible in a scan but quite striking with a hand lens. The total number of eggs is around ten.'
 

It was coincidence that I was also sent another leaf photo (lower photo) with a black/brown blotch - this time on Populus nigra (Black Poplar) and this too is probably a Zeugophora species.

This mine was found by David Manning on 27.x.2003 in Flint's Wood, Riseley, Beds (VC30).
 

Newsletter of leafmines.co.uk                                                                                                                                                                    November 2003 December 2003