(insect pollination) * Pollination by pollen carried on insects. Insect-pollinated plants need to be able to attact the pollinating agent and provide a suitable landing space for it and then deposit pollen onto and collect pollen off the visitor. Insects may be attracted to a flower through the provision of food, by pseudomating signals (for example, some orchids mimic the shape, colour, and odour of the female insect), or by provision of brood or shelter sites. Pollen itself may be provided as the food source as it is protein rich, but it needs to be produced in quantities sufficient to offset the loss. More often nectar is offered as a high-energy food. This is usually secreted from a nectary so placed relative to the reproductive parts that pollen collection and deposition is ensured. Fats, oils, and water are also used to attract pollinating insects. Adequate landing sites may be provided by increase in individual petal size, by increase in size of all the petals, or by the clustering of flowers into a compact inflorescence, such as an umbel. Recognition of the plant by the pollinating insect is achieved through secondary attractants, such as brightly coloured petals or insect-like movements. Special arrangements of the reproductive parts can be seen in many insect-pollinated species. Flowers that can be pollinated by a number of different insects are termed allophilic or promiscuous while those that can only be pollinated by one specific agent are termed euphilic (see mutualism). Some flowers may deposit pollen all over the agent but more specialized flowers deposit pollen only on certain areas of the vector. The pollen grains tend to be heavily sculptured and sticky in order to adhere to the agent's body. Compare anemophily , hydrophily. |
