rearing leafminers

[Nieukerken, E.J. van]

	Re David Smith's request:

	For rearing leafmining Lepidoptera there are a few points to
consider first:
	1. The type or taxon of leafminers 
	2. the pupation site
	3. the climate
	4. the voltinism

	The advises given by Maitland Emmet are good, but often more
complicate than needed. Moreover they apply mainly for the species of the
maritime climate of western Europe.

	In general Gracillariidae which make folded mines (Phyllonorycter,
Cameraria) and pupate inside the mine are the easiest to rear. Just keep the
leaves or cuttings with the mines in plastic boxes (e.g. ice-cream boxes)
covered with netting (or glue some netting in a hole in the lid). In summer:
spray regularly and the moths will come out easily. In winter: keep outdoors
until spring, the moths will be swarming after a few days/weeks when you
bring the boxes indoors. Spray now and then.

	You can also rear isolated mines in glass tubes with cotton wool.
Especially important when you want to identify single mines or parasites. I
also now and then have reared them in closed containers, but moulding is
bound to occur more easily.

	More difficult are Nepticulidae (my specialism) and some other
groups which pupate outside the mine. Most will pupate in the soil in
nature. These are best reared in closed containers. I use jam jars with a
small layer of flower-peat. To be absolutely sure that nothing emerges from
the earth, the peat/earth could be sterilized.
	It is very important to remove all leaves when the mines are
vacated, otherwise they start to mould (also the mines can then be kept for
the collection) . Also do not use paper labels: they are bound to mould
away. Instead make labels on plastic (e.g. pieces of coffee cups).
	Nepticulidae are best collected when the larvae are in their final
stage, when still small it is more difficult. 
	For the smaller ones it sometimes helps to put the petioles of the
leaves in a small plastic tube with water, through a hole in the lid (e.g.
Eppendorf tubes). This keeps the leaf fresh, and the larva can continue to
feed.

	Some people prefer Sphagnum moss, but in my experience it is not
better than earth or peat.

	The rearings should be kept cool during winter: in an out-house, or
in the fridge (give them a cold treatment with a period below zero). In the
tropics there is often no diapause.

	In drier climates, such as the Mediterranean Region (or California),
Nepticulidae can do with less moist and pupate easily on paper tissue or
toilet paper. The pupae can be kept with the paper in smaller plastic
containers with a closed lit. Just add a few drops of water, and the
humidity will remain fairly good. When condensation starts on the walls it
should be wiped out. Too dry breedings should be lightly moistened.
	Note that many species in these areas have a summer diapause, so it
might take long (more than 6 months) before anything emerges!

	The most difficult leafminers are those that change feeding from
leafminer to external feeder (e.g. Bucculatrix). They should be provided
with fresh plant material, and can probably be best reared in breeding
cages. I have little experience with these.

	I hope this helps, good luck with rearing!

yours sincerely,

Erik J. van Nieukerken

curator of Entomology / 
editor Tijdschrift voor Entomologie

National Museum of Natural History Naturalis
dep. of Entomology
PO Box 9517, 2300 RA Leiden, Netherlands

direct phone: +31-71-56 87 682 (secretary ..622)
fax:      +31-71-5687666
e-mail:  nieukerken at nnm.nl <mailto:nieukerken at nnm.nl>