The leaf and stem mines of British flies and other insects
 

(Coleoptera, Diptera, Hymenoptera and Lepidoptera)

by Brian Pitkin, Willem Ellis, Colin Plant and Rob Edmunds

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PLANTS AND THE LAW

All wild animals and plants are given some protection. Under the Wildlife and Countryside Act, 1981, which covers Britain, it is illegal to dig up any wild plant without permission from the owner or occupier of its habitat. Some very rare plants are totally protected by the Act, and removal of any part of them is an offence. If required for further study or identification, wild flowers known to be common or plentiful in the locality may be picked; but in general, wild flowers should be left for the enjoyment of other people. Equivalent provisions for Northern Ireland are contained within the Wildlife (Northern Ireland) Order 1985 and the Nature Conservation and Amenity Lands (Northern Ireland) Order 1985. Where a host plant is protected under any of the above provisions, this is noted in the keys to mines

A Code of Conduct for the conservation and enjoyment of wild plants, giving further details of the Act, including the list of protected species, is available from the Botanical Society of Britiain & Ireland (BSBI).

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COLLECTING MINES

Dipterous miners are recorded throughout the British Isles. Mines may be sought wherever their host plant or plants grow. Some mines are very obvious and will be easily discovered e.g. those of Phytomyza ilicis on Holly (Ilex) and Pegomya species on Docks and Sorrels (Rumex) and Knotgrasses (Polygonum), others are difficult to find without a thorough and extensive search e.g. those on grasses and sedges

On discovering a leaf mine, you should endeavour to identify its host plant in situ, preferably by reference to a field guide. British wild flowers may be identified using either one of the numerous published floras such as Stace (2010) New Flora of the British Isles and Francis Rose's 'The Wild Flower Key British Isles-N.W.Europe with keys to plants not in flower' first published by Frederick Warne in 1981 and reissued in 1991 or online at www.botanicalkeys.co.uk/flora/content/SEARCH.ASP. It is usually easier to identify flowering plants when in flower. Unfortunately not all mines occur when the host plant is in flower, so it may be neccessary to visit the site again to re-examine a host plant. Howevr, The Vegetative Key to the British Flora by John Poland and Eric Clement [published in 2009 by the BSBI] is also very useful. There is a downloadable list of additional publications by the BSBI.

If possible take a photograph or digital image of the host plant in situ. Where it legal to do so, remove mined leaves and stems avoiding unneccessary damage to the host plant. Transfer the mined leaves and stems to a polythene bag in which you have placed a sheet of white paper to absorb excessive moisture. If you have been unable to identify the host plant, collect a flowering stem and some undamaged leaves and place them in the polythene bag with the mined stems or leaves for later examination. If you have been able to identify the host plant make a note of the its identity. Write collection data, such as the name of the host plant, location, date of collection, using a pencil on a slip of paper and place this inside the bag. Keep the bagged mines out of sunlight to avoid overheating.

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IMAGING MINES

Host plants and mines may be photographed using either a film or digital camera. The later are preferable because of their immediacy. My earliest images were taken using a Nikon F801 with a 60 mm macro lens on Kodachrome 25 ASA slide transparency film which were subsequently scanned using a Canon Canoscan 2700F. I now use a Nikon D80 with a 60mm macro lens. However, any digital camera with the ability to capture images of 3 Megapixels or more and a zoom lens allowing at least 1:1 image to subject ratio is suitable.

Whether film or digital, your resulting images will provide you with a permanent record of the host plant's and mine's appearances when fresh, when it is usually easier to observe the larva or larvae and frass inside the mine.

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REARING

On return to your base, carefully remove the mined leaves and/or stems you have collected from the polythene bag and photograph or digitally image them on a white background and, if possible, on a back-lit sheet of glass. Transmitted light passing through the mine will often reveal detail not apparent using reflected light. Document your images carefully.

Any unoccupied mines, once photographed or digitally imaged, should be pressed using a plant press. Remember to document them. Return any occupied mines to the polythene bag, seal it and keep it out of the sunlight in a cool place to await the emergence of the miners (adults or larvae) or any parasitoids. If the mines are incomplete when collected you may wish to take further photographs of the mines as they develope.

Species pupating within the leaf, e.g Chromatomyia species, will usually emerge within a couple of weeks. The pupae of species which pupate externally can be carefully transfered to a small plastic box lined with white paper using a fine moistened paint brush. The white paper will enable you to observe the puparia more easily. Some miners emerge from the puparium within a week or two, but others with only a single generation per year or towards the end of the year will overwinter. The later are usually very difficult to rear out!

Leaves and stems with empty mines, if not decomposing, should be pressed and retained.

Brian Elliot (2007) published a short paper on rearing leaf miners (http://www.leafmines.co.uk/pdfs/news2.pdf).

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PRESERVING MINES

Pressed mines should be mounted on archive quality herbarium sheets, documented and stored in a dry place. The collections of mines at the Natural History Museum are mounted on folded A4 paper using white gummed paper strips. Data is printed on the outside of the folder. The folders are stored flat in card boxes in steel cupboards.

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PRESERVING ADULT FLIES

Adult flies may be preserved by pinning them using micro pins or by gluing them to a card mount or directly to a pin.....

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DISSECTING ADULT FLIES

In order to identify adult flies it is usually neccessary to remove the abdomen and dissect the genitalia for slide mounting .....

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SLIDE-MOUNTING

Larvae, pupae, adults and dissected genitalia may be slide-mounted.....

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IDENTIFYING ADULT FLIES

There are some keys for the identification of British flies published as Handbooks by the Royal Entomological Society of London, although they are all considerably out of date:

d'Assis Fonseca, E.C.M., 1978. Dolichopodidae.

Freeman, P., 1983. Sciarid flies (Sciaridae).

Smith, K.G.V., 1989. An introduction to the immature stages of British flies. Diptera larvae, with notes on Eggs, puparia and pupae.

Spencer, K.A., 1972. Agromyzidae.

White, I.M., 1988. Tephritidae.

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PRESERVING HYMENOPTERA PARASITOIDS

The methods for preserving parasitoids have been described in detail for Chalcidoids by John Noyes at nhm.ac.uk/research-curation/projects/chalcidoids/collecting1.html

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Last updated 15-Nov-2017  Brian Pitkin Top of page