Chilling is a cost-effective and safe method of immobilising flies in Drosophila experiments. However,
should condensation form on the plate, it would be fatal to the flies. Here we describe a modified cooling
method using reusable commercial ice pack(s) (ca. 400 ml, 2–3 cm tall) rather than crushed ice. The
ice pack is covered with a piece of filter paper which absorbs the condensed water formed on the cold
surface, and the moistened filter paper does not wet the wings of flies inverted onto it. An ice pack
(ca. 400 ml) takes effect in at least 1 h, and its height is shorter than the maximum specimen height of
a dissecting microscope, so that flies can be checked while they remain on the cold surface. This method
overcomes the disadvantages of the indigenous cooling anaesthetising approach and makes it practically
feasible. We also describe an easy-to-make fly-transferring toolkit which will greatly facilitate fly transferral
when it is combined with our chilling method. In our design, the flies were directed out of a vial
by a blue pipette tip, which is inserted in a foam stopper and channelled down into another vial by a
glass funnel inserted in another foam stopper which is escape-proof.

• A Modified Cooling Method and its Application in Drosophila Experiments

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