Insect Pollinators: Matchmakers of the Plant World
Photo StoryPublished : Aug 19, 2022Updated : Sep 30, 2023
Roughly 80 per cent of all flowering plants need the help of animals to reproduce. Tiny pollinators like bees, beetles, butterflies, and flies ensure that flowering plants continue their lifecycle
Text by: Samuel John
Roughly 80 per cent of all flowering plants need the help of animals to reproduce. Tiny pollinators like bees, beetles, butterflies, and flies ensure that flowering plants continue their lifecycle
Since the dawn of life on Earth about 4 billion years ago, living things have evolved fascinating ways to reproduce. Fast forward a few billion years from that single-cell reproduction, and you find jumping spiders dancing to attract a mate, baya weaver birds constructing nests to impress a potential suitor, and a primate species with the same end-goal as the baya, writing conceited self-descriptions on matrimonial websites. In the world of flowering plants, reproduction of many species occurs only with the help of dutiful matchmakers. Roughly 80 per cent of all flowering plants require the assistance of animals to reproduce. Through pollination, pollen from the anther (male parts) of a plant’s flower reaches the stigma (female parts) on the flower of another plant of the same species. This enables reproduction and the production of seeds — the plant’s first step to creating new life. As primary food producers, plants play an integral role in ecosystems everywhere.
Evolutionary processes have crafted mind-boggling relationships between pollinators and plants. In tropical countries like India, these incredible relationships and processes occur everywhere, from dense evergreen jungles to concrete cities. Even in a highly urbanised space, tiny pollinators are busy ensuring the continuity of flowering plants and the lives that depend on them. Bees explore flowers in home gardens; flies buzz onto flowers around homes and in open urban spaces; fig wasps actively travel between neighbourhood fig trees; moths and butterflies visit flowers on pavements and waysides. Aside from their critical ecological contributions, pollinators make vital economic contributions. Their primary role is to pollinate the crops we depend on for food and trade. A study published in the Indian Journal of Agricultural Sciences links an estimated annual market value of crops worth $84 billion to animal pollinators — with over $22.5 billion linked directly to insect pollinators.
Bees are perhaps the most well-known pollinators on Earth. We all know that bees go from flower to flower, collecting nectar to take back to their hive and turn into honey. Interestingly, only 8 of the 20,000 species of bees globally are honeybees (bees that build hives and store honey like the two honeybees on the left). While most bees do not produce honey, they all rely on flowering plants for nutrition — feeding on nectar gives them energy, while pollen provides them with protein and other vital nutrients. In return for plant nutrition, hungry little bees like the small carpenter bee (2) pick up pollen grains from flowers on their hairy bodies. When the bee visits another plant of the same species, it unwittingly sprinkles these pollen grains onto the stigma. Solitary bees, like the carpenter bee, share an interesting relationship with self-pollinating plants — the vibration from their wings as they sit atop the flower helps shake pollen loose and consequently enables pollination of plants like tomato or eggplant. Photos: Hayath Mohammed (1), Jithesh Pai (2)
Cover photo: Ripan Biswas
Beetles also visit flowers for their nutritional needs. Unlike bees, they primarily visit flowers to eat pollen and occasionally petals. Many studies suggest that animal-mediated pollination likely evolved ~140 million years ago. Beetles evolved roughly 200 million years ago and are widely regarded among the first animal pollinators of flowering plants. There is fossil evidence of a beetle (Cretoparacucujus cycadophilus) covered in pollen from ~100 million years ago. Another interesting feature of beetles is their incredible diversity. There are currently 400,000 species of beetles known to science (roughly 25 per cent of all known animals). Some estimates suggest that beetles play a role in pollinating at least 90 per cent of flowering plants. And around 184 species of flowering plants are pollinated almost exclusively by beetles. Photo: Jithesh Pai
As butterflies go through their lifecycle, they share an interesting relationship with plants. As adults, they feed on nectar and pollen from flowers. When sucking up a healthy portion of nectar, pollen grains attach themselves to their bodies (1). These minuscule specks of pollen are then transported to other flowers the butterfly visits. Butterflies extract a few more favours from plants in exchange for the pollination service: they use the undersides of leaves to safely lay eggs. Once the eggs hatch and larvae, like this crimson rose caterpillar, emerge (2). For larvae, the primary source of food is their host plant’s leaves. After they pupate into butterflies (3), they begin the search for nectar, and pollination begins all over again. Photos: Girish Gowda (1), Samuel John (2,3)
Pollination happens round the clock. During the night shift, moths take up the pollination baton. Adult moths, much like butterflies, typically feed on the nectar of flowers with their long proboscis (straw-like mouthpart). While feeding, their hairy bodies pick up and drop pollen grains between flowers. The timing of their contribution to pollination is particularly critical for plants like the four o’clock plant (Mirabilis jalapa) which only blooms around dusk. Photo: Ripan Biswas
Wasps are another group of actors that play an important role in the world of pollination. Most species of Ficus (fig trees) are pollinated exclusively by one or a few species of wasps. In this delicately balanced relationship, neither the fig nor the tree can procreate without the other’s help. Outside the mysterious world of fig wasps, other wasp families like the cuckoo wasp family (Chrysididae) are important generalist pollinators. Cuckoo wasps are parasitoid wasps. Despite their carnivorous nature at the larval stage, adult cuckoo wasps like the ones seen in the images above feed mainly on flower nectar. Their adult dietary habits make them prolific pollen carriers for a wide variety of plant species. Photos: Ripan Biswas
Flies (Diptera) exist in nearly every corner of the world. They are an incredibly diverse group with over 150,000 described species (conservative estimates suggest that global fly diversity is likely to be around a million species). In addition to being excellent decomposers in their larval stage, adult soldierflies (1) regularly visit flowers for nectar, and generously transmit pollen from one plant to another. A paper by Ssymank et al. suggests that flies may contribute significantly to pollination in nearly every ecosystem worldwide. Besides enhancing pollination efficiency in ecosystems with other pollinators like butterflies and bees, flies may be exclusive pollinators in harsh habitats (like high elevations or the arctic) where other pollinators are absent. Studies from around the globe have found that hoverflies (2) are significant contributors to pollination. In India, they are essential pollinators for crops. In addition to their pollination services, many hoverfly species in the larval stage actively feed on aphids and other herbivores that feed on plant material — acting as natural guards for the plant’s health. Photos: Hayath Mohammed (1), Jithesh Pai (2)
There is a balance between the processes that promote and deter pollination. Ants, for instance, also visit flowers for nectar as a source of nutrition (3). However, studies have found that they likely impact pollination negatively as their tiny frames can go in and out of flowers without picking up pollen. When they do pick up pollen grains, pollen viability is often reduced significantly because of the antibiotic chemicals ants secrete as a defence against parasites. At the other end of the process, pollinators face dangers when visiting a flower. Predators like crab spiders (1,2) are built to camouflage within flowers where they prey on unsuspecting invertebrate visitors. In these images, a blue-banded bee and a moth can are in the crab spider’s death grip.
While natural deterrents strike a balance, human influences have far more catastrophic effects. The rampant use of pesticides in agriculture, drastic modifications to natural habitats, and pollution are some ways in which we upset this delicate balance. Photos: Girish Gowda (1,2), Samuel John (3)
is the co-founder of Spiders and the Sea, a social enterprise working towards bridging people and nature - through research, outreach and creative storytelling.
