Flowers are surprisingly sensitive, particularly their male parts, the stamens. Many plant species exhibit touch-sensitive stamen movements that can be repeated multiple times. When insects visit Berberis and Mahonia flowers for nectar, they’re met with stamens that bend over to cover them in pollen. This sudden action often startles the insects, prompting brief visits and conserving the flower’s nectar and pollen. The insect then moves to another flower, where it transfers the pollen to female organs, aiding cross-pollination.
In the case of the orchid Catasetum, an insect encounters a more aggressive reaction. It is hit by a pair of sticky pollen bags that eject at high speed, sticking to the insect, which is then thrown out of the flower.
Similarly, Australian triggerplants (Stylidium) use a club-shaped organ to hold their reproductive parts. When touched, this organ swiftly swings 180 degrees in a tenth of a second, covering the insect in pollen and collecting any it carries. The trigger then resets quickly, preparing for the next pollinator.