- Hoverflies are the second largest non-bee pollinators in the world, though they closely resemble bees and wasps.
- Urbanised landscapes, reduced floral resources, low quality breeding spots and accelerated pesticide usages are some of the key drivers in declining hoverfly populations.
- Hoverflies are a significant ecosystem service provider for ecological sustenance.
- The views in the commentary are that of the author.
Insects are the backbone of global food systems. Pollinating over 70% of cultivated crops and 90% of flowering plants, insects are one of the major ecosystem service providers, offering services valued around US$235 to 577 billion. Yet most discussions on pollination centres exclusively around bees, side-lining other crucial pollinators in research, policy and public attention.
With plummeting pollinator populations worldwide, focus needs to be shifted onto other overlooked pollinators like flies, wasps, beetles, moths and butterflies. Flies stand out as the second line pollinators, next to bees, bolstering 551 species of plants from 71 families. Some of the families of flies involved in pollination are Syrphidae (hoverflies), Bombyliidae (beeflies), Calliphoridae (bottle flies), Tachinidae (tachinid flies) and Anthomyidae (root maggot flies). Among these, hoverflies offer much efficient pollination in terms of adaptability and diversity. Thriving in meadows, peats and densely packed urban settlements, hoverflies glide across farms and forests ensuring pollination with utmost precision.
What are hoverflies?
Hoverflies are members of the Syrphidae family of Diptera. With over 6,000 species in 377 genera across the globe, they thrive everywhere except the harsh climates of tundra and deserts. They showcase diverse life cycles and remarkable mimicry, yet their ecological roles are often underappreciated.
As their name suggests, hovering is a signature behaviour of these flies, and is associated with ‘food hunt’. However, this plays out differently for males and females. For instance, females drift amongst the foliage to inspect a suitable environment for laying eggs, whereas males defend their territory through their aerial waltz.
These flies, unlike other dipterans, exhibit Batesian mimicry, where harmless species mimic harmful ones to protect themselves from predators. Closely resembling either a bee or wasp, even buzzing like one, hoverflies are often dismissed on sight. Certain species of genera Spilomyia, Temnostoma and Volucella exhibit similarity to wasp antennae to deceive enemy, while Eristalis species, commonly called as droneflies, copies their honey bee counterparts — one of the most convincing mimicries of these flies, even puzzling experienced bee keepers.
Nevertheless, science reveals them to be imperfect mimics, impacted by life span, body size and predation pressure. But these doppelgangers can be delimited. With large globular eyes covering almost 80% of their head, stubby antennae and rounder lower body, offers a distinct body silhouette from their stinging twins. Their imitation surpasses the typical expectation. If threatened, these flies raise and forcibly flare out their body, flawlessly copying a stinger, showcasing a spectacular strategy of behavioural adaptation. Apart from their uncanny similarity to a wide range of hymenopterans like honey bees, bumble bees, wasps etc., their geographical distribution and emergence also resonates with their counterparts, making their evolution a topic of discussion.
Why does hoverfly matter?
Flies have a bad reputation of being disease carriers on earth. Yet not all of them have to be looked down with disgust. Some like hoverflies hold aloft critical responsibilities in the ecosystem, more than one can fathom. From pollination to pest control and acting as nature’s sanitation crew, these flies offer a wide array of provisions to nature and humans.
Hoverfly adults are generalist flower visitors, feeding pollen grains and nectar. While nectar provides male hoverflies energy for long fights and stability; females consume pollen grains for completing their reproductive development and egg laying. These flies are quite fond of open-accessible flowers of plant families like Apiaceae, Asteraceae, Brassicaceae, Rosaceae, Ranunculaceae, and Lamiaceae. A strong visual colour palette of yellow and white flowers also augments their flower selection efficacy. A 2005 study states hoverflies as a noteworthy pollinator, not just of wild plants but also commercial crops contributing to 52% to the global agricultural economy. Carrying large pollen volumes worth billions of dollars, hoverflies steal the spot as world’s second largest pollinator after wild bees.
Even in higher elevations and wetlands, hoverflies take command where pollinators like bees are constrained by challenging weather. Jayita Sengupta, an expert working on pollinating diptera from Zoological Survey of India validates that some ecologically exclusive and vulnerable plants rely on hoverflies for propagation. For example, plants like orchid Epipactis veratrifolia, chemically imitate aphid signals to attract hoverflies for pollination. Also Himalayan species of Primula and Rheum nobile, and wetland dwellers like Caltha palustris and Menyanthes trifoliata are also dependent on syrphids for efficient pollination.
In the world of a fly, 60 out of 130 families migrate, with hoverflies demonstrating the highest rate of activity and flower visits. A study conducted by University of Exeter on marmalade flies, reveals an impressive pollen transport ability of these flies. Flying over long distances, syrphids ensure not just plant blooms but sheer hope for sustaining isolated plant communities’ survival. Surprisingly, the speed of migration is unaffected by abdomen size. But on the contrary, these flies throttle their speed to a maximum while maintaining a pace which facilitates their flight over longer distances relentlessly.
Their duality in life and purpose are equally curious considering their ecological duties.
After mating, depending on species, female flies lay eggs near their food source. Egg deposition is also modulated by ‘enemy-free space’ where predators like parasitic wasps are less and spaces preoccupied by other hoverfly’s eggs are abstained, preventing competition and cannibalism amongst larvae. Unlike adults, larvae (also called maggot) have diverse diets exhibiting predatory, saprophagy, phytophagy and myrmecophagy. The predatory maggots, for instance, consume insects, predominantly sap sucking pests like aphids and other soft bodied bugs like thrips, psyllids, caterpillars, eliminating up to 70-100% of pest populations, making them excellent allies for biological control. A recent discovery of a new species from India, Ischiodon aegyptius with predatory instincts in tandem with species like Episyrphus balteatus and Xanthandrus, hints at a rich diversity for hoverflies in India, waiting to be explored taxonomically and ecologically. It is expected that further research into their behaviours will undoubtedly open new areas of their application as biocontrol agents in Integrated Pest Management in future.
Hoverflies’ ecological impact stretches beyond flower patches, extending from land to water. Aquatic larvae of Eristalis species (rat-tailed maggots) reside in stagnant waters like sewages and lagoons with depleted oxygen content, acting as nutrient cyclers breaking down organic matter, keeping the waters clean. One such example is the thick legged hoverfly, Syritta pipiens forages on organic debris acting as a vital ecological recycler.
A call for action
Globally, pollinators are at serious risk due to shifting climate, changing landscape, loss of land heterogeneity, invasive species, dwindling quality of pollinator breeding sites and rampant chemical usages in agriculture. Recognising and conserving non-bee pollinators like hoverflies that exhibit more resilience is crucial in the Anthropocene.
Conservation of hoverflies demands a blend of practical actions and context specific solutions. A 2017 paper published by Royal Entomological Society suggested boosting hoverfly populations based on larval types. As per their studies, upgrading floral density had directly escalated the abundance of predatory hoverflies. Reducing chemical pesticides, sustaining floral diversity near farmlands and patchy forests, mapping microhabitats suitable for larval forms, encouraging the citizens to build a ‘hoverfly lagoons’ — planting native flowering plants and leaf litter arrangements with water resources etc., is expected to conserve the population of hoverflies. Global initiatives like Veteran Tree Hoverflies – Conservation Action Plan 2023-2030 provide guidelines and models to implement local programs and management regimes to promote hoverfly conservation.
“In India, hoverflies remain significantly under-recognized as essential pollinators due to several longstanding gaps in research and awareness,” says Sengupta. According to her, hoverflies receive almost no attention in national pollinator programmes or conservation policies, collectively depriving them of the needed recognition due to limited taxonomic knowledge, restricted use of molecular analysis and scarce ecological studies with no standardized monitoring protocols.
Despite their indispensable roles, hoverflies are often overshadowed by “charismatic pollinators”. Their finesse is indeed their strongest suit, yet seldom mentioned in conservational debates and policy discussions.
The author is a postgraduate researcher in zoology with interests in insect science, conservation and wetland ecology.
Citation:
- Peris, D., Ollerton, J., Sauquet, H., Hidalgo, O., Peñalver, E., Magrach, A., … & Pérez‐de la Fuente, R. (2025). Evolutionary implications of a deep‐time perspective on insect pollination. Biological Reviews.
- Leavey, A., Taylor, C. H., Symonds, M. R., Gilbert, F., & Reader, T. (2021). Mapping the evolution of accurate Batesian mimicry of social wasps in hoverflies. Evolution, 75(11), 2802-2815.
- Dunn, L., Lequerica, M., Reid, C. R., & Latty, T. (2020). Dual ecosystem services of syrphid flies (Diptera: Syrphidae): pollinators and biological control agents. Pest management science, 76(6), 1973-1979.
- Moquet, L., Laurent, E., Bacchetta, R., & Jacquemart, A. L. (2018). Conservation of hoverflies (Diptera, Syrphidae) requires complementary resources at the landscape and local scales. Insect Conservation and Diversity, 11(1), 72-87.
Banner image: A marmalade hoverfly (Episyrphus balteatus). Image by Thejavikho Gwizantsu Chase.
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