The waxy layer of the vitelline membrane was then removed by sequential treatment with isopropanol and hexane.
After the 24-h collections, volatiles were eluted from the traps with 1 ml hexane (99.5%).
The hexane was evaporated and the oil weighed.
The required amounts and ratios of synthetic compounds dissolved in 200 l hexane were applied onto the inner surface of the rubber septa.
At no time did parasitoids physically touch the central filter paper discs that had received no treatment or treatment with hexane alone.
Control treatments with 1 ml droplets of hexane alone did not stimulate aphid movement.
Significantly fewer males were caught in control traps impregnated with hexane only.
This was diluted with hexane for easier application; the hexane soon evaporated.
