As Bengaluru’s temperatures peaked at 38.5°C in April this year, natural landscape architect Akshay Vidhate stood in his terrace garden among 30 varieties of flowering plants. The air was eerily quiet. He noticed the absence of the familiar buzz of wild honey bees in his garden.

Vidhate turned an empty bottle into a makeshift feeder, filled it with a light sugar-water mixture, and hung it in the shade. “For the first few days, nothing happened,” he recalls. “Then, suddenly, there were bees everywhere. Now they arrive every morning, almost on schedule.”

Vidhate’s experience reflects a slow shift unfolding across India’s urban landscapes — the transition from environments that naturally sustain wild, open-air bees to ones that increasingly require human intervention to keep ecosystem functions alive.

Native bees face challenges in cities

Global pollinator research has focused heavily on the Western honey bee (Apis mellifera), a cavity-dwelling species managed in commercial hives. However, pollination in India’s agricultural and urban ecosystems depend largely on free-living wild bee populations such as the dwarf honey bee (Apis florea) and giant honey bee (Apis dorsata).

Between these two species, the native dwarf honey bee serves as a foundational ecological safety net. “The size of a pollinator is often proportional to the size of the flower it pollinates,” explains Apoorva B.V., an apiarist and founder of HoneyDay Bee Farms and the Hive Trust, who has spent over a decade tracking wild bee colonies across Karnataka. Because of its small size, the dwarf honeybee, A. florea functions as a highly versatile, generalist pollinator. “Its size allows it to access tiny blossoms in the backyard kitchen gardens, wild weeds, and urban fruit crops such as gourds, drumsticks, and mangoes — flowers that larger species like the giant rock bee (Apis dorsata) often cannot effectively utilise,” he says.

Despite their important role in local food security, these honey bees are facing a quiet crisis. Studies point to urbanisation, changing weather patterns, and pesticide use as key drivers of bee population decline.

A study on the functional diversity of farmland bees across rural and urban landscapes in Bengaluru, published in Ecological Applications in 2021, found that overall bee abundance and the abundance of social bees — which accounted for 85% of all bees recorded — declined with urbanisation, threatening crop pollination. In the study area, four social bee species were recorded: the Indian honey bee (A. cerana), the dwarf honey bee (A. florea), the giant honey bee (A. dorsata), and stingless bees (Tetragonula spp.). The researchers found that “A. florea strongly declined with increasing gray area (urban construction), thereby explaining the overall negative response of social bees,” the study noted.

“Increasing temperatures and water crises are causing significant ecological changes,” says Axel Brockmann, associate professor at the National Centre for Biological Sciences (NCBS), Bengaluru. He notes that when local temperatures permanently exceed a species’ thermal tolerance range, wild populations are forced to retreat to cooler, higher-altitude regions such as the Himalayas. Because India lacks a centralised, long-term monitoring database for wild insects, tracking these population shifts remains difficult. “There is little research on how honey bees suffer from heat stress and pollution in India,” Brockmann says.

Genetic blueprint of bee behaviour

Most recently, a comparative baseline study published in the Journal of Experimental Biology mapped the internal genetic and hormonal mechanisms of these tropical insects — the molecular blueprint that governs how a bee develops, behaves, and survives. The study established the first comprehensive molecular profile of the dwarf honey bee, revealing how its internal chemical clock regulates survival in an environment without structural protection.

Led by Sruthi Unnikrishnan of National Centre for Biological Sciences (NCBS) and co-authored by Brockmann, the research offers a molecular explanation for the species’ current vulnerability. Unlike cavity-nesting bees that live protected inside dark tree hollows or managed hives, the dwarf honey bee builds its nests entirely in the open, suspending a single comb from exposed tree branches or garden shrubs. The study found that these open-air bees maintain high levels of a protective protein called vitellogenin throughout their lives. This biological trait enables the colony to form a constant “living curtain” of tightly packed workers that shield the exposed nest, helping protect the brood from predators, parasites, and harsh weather while also aiding temperature regulation.

The researchers also found that dwarf honey bees develop more slowly than cavity-dwelling species, taking more than three weeks to transition from nursing duties inside the nest to foraging for food outside.

According to the researchers, this biological rigidity stems from an ancient evolutionary trade-off between open-air and cavity nesting. Bees that nest safely inside enclosed cavities, such as Apis cerana, do not need to devote large numbers of workers for nest defence. Freed from this responsibility, a colony can allocate more workers to brood care, enabling faster population growth. If environmental shocks kill off foragers, these colonies can replace them relatively quickly with newly emerged workers.

In contrast, Apis florea is constrained by its open-air lifestyle. A significant proportion of the colony must continuously serve as a protective “living curtain”, leaving fewer workers available to rear brood. As a result, colony growth is slower. To compensate for this limitation, the dwarf honey bee’s internal developmental programme staggers worker maturation, creating a buffer against population losses. While this strategy has helped the species survive for millions of years, it also means colonies are slower to recover when large numbers of foragers are lost.

Floral diversity a key factor

Evidence from a regional field study in Karnataka shows that dwarf bee colony size, nest volume, and honey production are closely tied to the availability of local flowering plants.

Across habitats studied, these parameters peaked during summer, when flowering was at its highest, underscoring the species’ dependence on abundant floral resources for growth and productivity. The study also found that colonies exposed to higher levels of disturbance were more likely to abscond and tended to be smaller, suggesting that Apis florea is highly sensitive to human activity.

This finding is particularly relevant in rapidly urbanising landscapes. As cities replace diverse green spaces with concrete infrastructure, flowering plants become increasingly fragmented and seasonal. When floral resources decline or colonies are repeatedly disturbed, dwarf honey bees have fewer options to recover, making them especially vulnerable to the combined pressures of urbanisation and climate stress.

Moreover, since dwarf bees take over three weeks to mature into foragers, a sudden toxic event can break a colony’s timeline. “A single instance of spraying pesticides will wipe out most of the foragers. The colony simply cannot replace its workforce overnight,” warns Apoorva.

Reimagining conservation

Historically, conservation policies have overlooked wild, open-air species that perform the ecological heavy lifting for urban green spaces through large-scale pollination. “Many people prefer managed honey bees or stingless bees (Trigona spp.) because they can be controlled, commercialised, and kept safely in boxes,” says M. Soubadra Devy, Senior Fellow at ATREE. “Dwarf bees have specialised open-nesting requirements, preferring thorny, brambly vegetation and scrubby habitats for protection,” she explains. Dwarf bees are free-roaming generalists that cannot be domesticated.

Urban crop yields might face severe strain in the absence of dwarf bees. “Ecosystems can temporarily buffer pollinator losses through ecological replacements—like when giant rock bees stepped in during a drought year when stingless bees were absent,” says Devy. “But if landscapes lose nesting spaces entirely, all bee species will decline, causing food yields to crash.”

Dhruba Naug, social insect biologist and professor at Colorado State University, explains that calculating a wild bee’s vulnerability is highly complex. “One might expect dwarf bees, with their low metabolic rate and slow life history, to be more affected by chronic stress (such as pesticide exposure),” says Naug. “Their slow developmental rate also means their population growth is low, leading to a slower recovery rate than other bees.”

Since open-nesting bees live completely exposed, they absorb the brunt of environmental degradation. “Open-nesting bees are more exposed to air pollution,” Naug notes. “Their health directly reflects local pollution levels, meaning these open nests could be used as urban biosensors.”

“Coexistence requires balance,” concludes Devy. “An urban pollinator policy should identify which habitats need protection and where relocation is necessary. Expert panels should assess risks, protect vital nesting sites, and safely relocate colonies to balance conservation with public safety.”

Banner image: A dwarf honey bee colony built on bushes and branches in Bengaluru. Image by Bharath Kumar A.K.

Read more: All gain, no pain with stingless bees in greenhouse farming

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Arathimenon Editor

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BiodiversityCities and TownsClimate ChangeEcologyImpacts of Climate ChangePlantsKarnataka

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