Study conditions

1) The containers with cages are kept at 23 ± 2°C with natural light, or added artificial light, in cloudy condition during the day.

2) The containers should be closed with a sheet of transparent plastic.

3) It is possible to keep the bees at a relative humidity close to saturation simply by wetting an absorbent sheet of paper on the bottom of the container with distilled water.

This system enables the evaluation of the influence of high humidities without wetting the cages. Thus, bees are prevented from contact with the water. Because of the high humidity, the sponges soaked with honey should be replaced every 6 - 12 h; otherwise, the bees continue to suck at the light with an increase of mortality possible in untreated controls.