Insect pollination

Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns (honey guides) leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromones. Insect pollinators such as bees have adaptations for their role, such as lapping or sucking mouthparts to take in nectar, and in some species also pollen baskets on their hind legs. This required the coevolution of insects and flowering plants in the development of pollination behaviour by the insects and pollination mechanisms by the flowers, benefiting both groups.

Many plants, including flowering plants such as grasses, are instead pollinated by other mechanisms, such as by wind.

The early spermatophytes (seed plants) were largely dependent on the wind to carry their pollen from one plant to another, and it was around 125 to 115 million years ago that a new pollination strategy developed and angiosperms (flowering plants) first appeared. Before that, insect involvement in pollination was limited to "pollination assistants", insects which inadvertently carried the pollen between plants merely by their movements. The real relationship between plants and insects began in the Early Cretaceous, with beetle-pollinated gymnosperms. The morphology of the first fossil basal angiosperms is similar to modern-day plants that are also fertilised by beetles. It seems likely that beetles led the way in insect pollination, followed by flies. Among the twelve living families of basal angiosperms, six are predominantly pollinated by flies, five by beetles and only one by bees. Nevertheless, traits such as sapromyophily (emitting the odour of carrion to attract flies) have evolved independently in several unrelated angiosperm families.

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