Experts diving flowering plants into two groups based on pollination. Some are pollinated by the wind. Others are pollinated by animals, particularly insects that go from flower to flower in search of nectar or pollen as food. Pollen sticks to their bodies and is transported to other flowers. Not every flower that insects find alluring possesses all the characteristics of attraction. Some are colourful, while others rely on fragrance or tastiness to gain attention.
Types of Pollinators
At its online "Pollination and Plant Families" page, the University of Cincinnati's (UC) Biology Department says, certain types of insects such as butterflies, moths, bees, beetles, wasps and flies are pollinators. What attracts an insect often depends on the insect's abilities.
For insects, one attraction is colourful blossoms. Bees select flowers not only by smell but by specific colours. UC says bees only see blue and yellow blossoms or the ultraviolet "nectar guides" that attract them like landing strips. Conversely, butterflies have a weak sense of smell, but see a wider range of bright colours.
The Flower Expert, an online site, says that one of the primary reasons flowers smell, whether fragrant or unpleasant, is "to advertise" to insects the availability of food in the form of nectar and pollen. It adds, "Another evolutionary scenario could be that insects that were able to successfully find a mate on a flower with a certain fragrance would return to a flower with that fragrance, looking for a mate."
To be rewarded with an insect visit, flowering plants must offer some kind of reward. More often than not, insects are hungry for nectar or pollen. Some can identify potential food sources both through fragrance and colour. Others rely on one sense, such as nocturnal moths, which can't see colours in the dark, but have powerful senses of smell.
Fragrant flowers don't always reward insects with food, according to UC. For example, it cites a particular kind of orchid that smells like the female of a certain species of wasp. When a male wasp smells the orchid, it is tricked into thinking it has found a mate.
Similar to the old popular lyric "you were meant for me," insect-pollinated flowers have diverse needs that in some cases can be met only by one insect. A good example is the cactus yucca, which is dependent on the yucca moth for pollination. UC says this moth is the only insect that is the "right size and shape to pollinate yucca flowers." In exchange, eggs are laid in the plant's ovary where baby caterpillars develop, dining on some of the seeds.