Entomophily

Transfer of pollen grains through the agency of insects is known as entomophily.

• Entomophily is a type of pollination in which insects act as the pollinating agents.
• Common insect pollinators include bees, butterflies, flies, beetles, wasps, and moths.
• In flowering plants, insects often visit flowers to collect nectar, pollen, or other rewards, and in doing so, they carry pollen from one flower to another.
• Entomophily supports pollination in many angiosperms.
• Common examples: Rose, Jasmine, Cestrum, Salvia, etc.

Floral traits that attract insects:

• Flowers are usually large, showy, and brightly coloured so that insects can easily notice them.
• Many flowers produce a sweet scent to attract pollinators.
• Flowers often contain nectar glands that provide food rewards for insects.
• Some plants bear many small flowers together in a conspicuous inflorescence, thereby increasing their visibility to insects.

Traits that help pollen transfer:

• The stigma is rough or sticky, so pollen can adhere easily.
• Pollen grains are often spiny or sticky and may be coated with pollenkit, which helps them cling to insect bodies.
• The position of the anthers and stigma is arranged so that an insect brushing against the flower picks up pollen and later deposits it on another stigma.

Special attraction patterns:

• Night-blooming flowers may produce a strong fragrance to attract moths; Cestrum nocturnum is one such example.
• Some flowers produce unpleasant odours to attract flies and beetles instead of bees or butterflies.

Pollination sequence

1. A flower attracts an insect using colour, scent, nectar, or grouped inflorescences.
2. The insect lands on the flower in search of food.
3. Sticky or spiny pollen grains attach to the insect's body.
4. The insect visits another flower of the same species.
5. Pollen is deposited on the sticky stigma, completing pollination.

Structural adaptations

• Large and colourful petals increase attraction.
• Nectar glands provide a reward and encourage repeated visits.
• Sticky stigma ensures easy pollen capture.
• Sticky or spiny pollen helps with attachment to insect bodies.
• Floral parts are positioned to maximise contact between the insect and the reproductive structures.

Functional adaptations

• Fragrance acts as a chemical attractant.
• Grouped flowers increase visual impact and make insect visits more efficient.
• Special floral mechanisms ensure a more certain transfer of pollen.

• Salvia has a special lever mechanism that promotes cross-pollination.
• When an insect enters the flower, the floral structure moves in such a way that pollen is deposited on the insect's body.
• On visiting another flower, the insect transfers the pollen to the stigma.

Lever mechanism in Salvia

Pollination syndromes

• Pollination syndromes are sets of floral features that attract a particular kind of pollinator.
• In insect-pollinated plants, colour, smell, nectar, stigma type, and pollen nature work together as a functional package.

Pollination contrivances

• Pollination contrivances are special structural or functional devices that help ensure pollination.
• These adaptations develop through the close relationship between plants and pollinators.

• Entomophily is the transfer of pollen by insects like bees, butterflies, flies, beetles, and moths; e.g., rose, jasmine, salvia.
• Insects visit flowers for nectar or pollen and carry pollen from one flower to another, aiding pollination in many angiosperms.
• Entomophilous flowers are large, showy, brightly coloured, scented, with nectar glands; small flowers group into a conspicuous inflorescence.
• Their stigma is rough/sticky, and pollen is spiny or sticky (coated with pollenkit) to cling to insect bodies.
• Special patterns: night-blooming flowers like Cestrum nocturnum attract moths by strong scent; some produce foul odours to attract flies and beetles.
• Salvia has a lever mechanism that deposits pollen on an insect's body for transfer to another flower's stigma, promoting cross-pollination.