Grip and slip: mechanical interactions between insects and the epidermis of flowers and flower stalks.

Flowers interact simultaneously with a variety of insect visitors, including mutualistic pollinators and antagonists such as florivores, nectar robbers and pollinator predators. The plant epidermis produces a range of structures, such as conical or papillate cells, that can help mutualists to grip the flower, while a variety of other structures, such as slippery wax crystals on the flowers or on the stems leading to them, are able to deter non-beneficial insects or behaviors. Modification of the floral surface can also aid pollination in unusual ways in some highly specialized interactions. In the case of the trap-flowers in species of Arisaema, conical cells aid pollination by being present on the spathe surface, but here they are modified in such a way as to decrease the pollinating insect's grip. We discuss a variety of these floral structural features that influence insect stability on the plant.