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Article

Distribution Patterns, Nesting Ecology and Nest Characteristics of the Stingless Bees (Tetragonula pagdeni Schwarz) in West Bengal, India

by
Ujjwal Layek
1 and
Prakash Karmakar
2,*
1
Department of Botany, Rampurhat College, Rampurhat 731224, West Bengal, India
2
Department of Botany & Forestry, Vidyasagar University, Midnapore 721102, West Bengal, India
*
Author to whom correspondence should be addressed.
Conservation 2025, 5(4), 63; https://doi.org/10.3390/conservation5040063
Submission received: 20 July 2025 / Revised: 4 October 2025 / Accepted: 20 October 2025 / Published: 30 October 2025
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Abstract

Stingless bees, particularly Tetragonula pagdeni, are vital for both ecosystems and the economy due to their pollination services and nest products. However, little is known about their nesting habits. This study investigated the nesting ecology of Tetragonula pagdeni in West Bengal, India. The species was found inhabiting a variety of landscapes, including agricultural, forest, rural, semi-urban, and urban areas, with a greater abundance in rural areas featuring mixed vegetation. Colonies, which were eusocial, perennial, and cavity-nesting, occupied diverse substrates, including tree trunks, building walls, rock crevices, electric poles, and field ridges—tree trunks and walls being the most common. Wild nests were located at heights ranging from 0 to 13.46 m, mostly around 2 m. Nest entrances varied in shape (circular, oval, slit-like, or irregular), with a longest opening axis of 10.50 ± 2.94 mm, and were oriented in multiple directions. Internally, nests measured 198.31 ± 86.36 mm in length and 142.73 ± 17.28 mm in width. Nests featured brood zones surrounded by honey and pollen pots, along with structure-supporting elements like the involucra and pillars. Brood cells were light brown and oval; those for workers and drones were similar, while queen cells were larger. Honey pots were light to dark brown, oval, dome-shaped, or irregular. Each involucrum was a thin, flat sheet, and the pillar was short, narrow, thread-like. These findings offer valuable insights into the distribution, nesting behaviour, and nest architecture of Tetragonula pagdeni, supporting its conservation and sustainable management.

1. Introduction

Stingless bees, belonging to the subfamily Meliponinae of the family Apidae, are a group of eusocial, small-sized honey-producing bees with vestigial stings. They are native to tropical and subtropical regions, and their distribution today largely corresponds to the Neotropical, African, and Indo-Malayan–Australian regions [1,2,3,4]. Approximately 56 genera of stingless bees, comprising over 600 species, are found worldwide [5,6,7]. In India, only a few stingless bee species (e.g., Lepidotrigona arcifera Cockerell, Lisotrigona cacciae Nurse, Tetragonula bengalensis Cameron, Tetragonula iridipennis Smith, Tetragonula pagdeni Schwarz, Tetragonula praeterita Walker, Tetragonula sumae Viraktamath, and Tetragonula vikrami Viraktamath) have been described [8,9,10,11]. As stingless bees are eusocial, generalist, polylactic foragers [12,13,14] and exhibit significant floral constancy [12,15], they are vital pollinators of several native and cultivated plants [16,17,18], and play a crucial role in enhancing crop yields (e.g., Citrullas lanatus (Thumb.) Matsum. & Nakai [18] and Solanum lycopersicum L. [19]) and conserving biodiversity. In addition, nest products (e.g., honey, pollen, propolis, and cerumen) have biological, pharmaceutical, and medicinal values [20,21,22]. Therefore, the study and management of stingless bees are becoming increasingly interesting and gaining attention.
The distribution and density of stingless bees vary among habitat types. Their most diverse habitats are natural forests, followed by secondary and utilised forests, farmland, and human-settled zones in rural and semi-urban areas [23,24,25]. Nest density depends on the availability of nesting substrates and food [26]. Although stingless bees are considered generalists in their nesting site selection, they still exhibit a degree of plasticity in their nesting habitats and nesting substrates [12,27]. Some species construct their nests in the abandoned nests of other social insects, such as those of ants and termites, which are found in either above-ground or below-ground environments [25,28]. Many other species solely nest in the cavities of tree trunks and walls [12,29] or in underground cavities [12,30,31]. Nest architecture varies among stingless bee species, exhibiting distinct characteristics in nest entrances and diverse designs in brood cell arrangements [27]. The nest entrance of stingless bees also varies in shape, length and colour [12,23,27]. Brood cells are arranged in either horizontal or vertical rows, with full combs or semi-combs, or in clustered cells [12,32]. The shape, size and arrangement of pollen and honey pots vary among species; in most species, they are arranged around the brood cells [12,23,25].
Tetragonula pagdeni is distributed in several countries, including India [8,9], Thailand [33] and Vietnam [34]. In the Indian state of West Bengal, it would be the first report of its high occurrence. The colony distribution pattern and nesting behaviour are less understood for this stingless bee species. Only a few research works on the nesting biology of Tetragonula pagdeni are currently available, and they are from other Indian states (e.g., Basanna & Rajanand [35]; Shaikh et al. [11]). This information is necessary for the sustainable management of stingless bees (i.e., meliponiculture). We aimed to study the nest distribution patterns, nesting habitats, nesting substrates, and nest architectures of the stingless bee species in West Bengal, India, through a systematic investigation of stingless bee colonies. We aimed to answer the following research questions: (i) Do the landscape compositions affect nest density of the stingless bee species? (ii) What are the nesting substrates for the bee species? How are the nest components organised within the nest?

2. Materials and Methods

2.1. Study Area and Stingless Bee Species

The present study was conducted between 2022 and 2025 in the Rarh region of West Bengal, India, encompassing the districts of Bankura, Birbhum, and Paschim Medinipur. This region is characterised by diverse vegetation zones, including agricultural lands, forested areas, rural settlements, semi-urban areas with human habitation, and fully urban environments. The region has a tropical climate with distinct seasons. Temperatures vary significantly, from hot summers (April–June) with daytime highs of 35–42 °C, to cool winters (December–January) with daytime temperatures of 7–15 °C. Annual rainfall averages around 1400 mm, mostly during the monsoon season (July–August).
The present study focused on the stingless bee species Tetragonula pagdeni, of the tribe Meliponini, family Apidae. This small eusocial species, with workers measuring approximately 5 mm in length, nests in cavities and forms perennial colonies (author’s own observation).

2.2. Survey on Nest Distribution Patterns

To assess nest density across different landscapes, the study area was divided into five landscape types based on key environmental variables (e.g., landscape features and vegetation), with slight modifications to the classification proposed by Wayo et al. [36]. The categories were: (1) agricultural areas, (2) forest areas, (3) rural areas, (4) semi-urban areas, and (5) urban areas. Agricultural areas were dominated by crop fields, with common species including Brassica juncea (L.) Czern., Coriandrum sativum L., Cucumis sativus L., Luffa acutangula (L.) Roxb., Momordica charantia L., Oryza sativa L., Sesamum indicum L., and Solanum melongena (L.). Shrubs such as Eupatorium odoratum (L.) R. M. King & H. Rob. and Xanthium strumarium L., together with trees like Borassus flabellifer L. and Phoenix sylvestris (L.) Roxb., were also recorded along the field ridges. Forest areas were primarily composed of tree species such as Acacia auriculiformis A. Cunn. Ex Benth., Eucalyptus tereticornis Sm., Shorea robusta Roth, and Terminalia bellirica [(Gaertn.) Roxb.]. Rural areas supported dense, mixed vegetation, consisting of both crops and trees, interspersed with village settlements. Semi-urban areas contained relatively sparse vegetation, dominated by planted trees, alongside moderate to high levels of human settlement. Urban areas, being highly modified by human activity, had very limited vegetation cover, restricted mainly to planted trees and ornamental species, and were characterised by moderate to high human settlement.
For the surveys, we semi-randomly selected plots measuring 100 m × 100 m and recorded the number of wild nests of the stingless bee species. We carried out surveys on sunny days between late morning and early afternoon (08:00–14:00 h), when stingless bees exhibit peak foraging activity, which made nest detection easier. Each plot was thoroughly surveyed in its entirety. In total, 150 observations were made (N = 10 × 5 × 3), covering five vegetation types with three zones sampled per type. Colony dispersion patterns (e.g., regular, random and clumped) of the stingless bee species were also observed.

2.3. Nest Substrates

After finding a nest, we recorded the type of substrate (e.g., tree, wall, or other) associated with each vegetation type. For tree-hosted nests, we noted the tree species, diameter at breast height (DBH), and the diameter at the nest site. For wall-hosted nests, the thickness of the walls was recorded.

2.4. External Nest Characteristics

During the survey, we measured the height of each nest (from ground level to the entrance) using a measuring tape and categorised them into six height classes: ≤2 m, >2–4 m, >4–6 m, >6–8 m, >8–10 m, and >10 m. The orientation of the nest entrances was recorded using a compass. We noted the presence or absence of an external tunnel (also known as an entrance tube); if present, its length was measured. The shape of the nest entrance (i.e., the outline of the opening) was documented, and the length of its longest axis was measured.

2.5. Internal Nest Characteristics

To study internal nest characteristics, we examined wild nests (n = 10) by cutting open the nest-holding substrates. Additionally, we observed the internal features of nests maintained in managed hives. Inside, we measured the length of the internal tunnels and recorded the dimensions of the cavities. For each type of nest component—brood cells, pollen pots, and honey pots—we documented their morphology and dimensions (n = 50 observations per component). Additionally, we estimated the density of each component type by calculating the number of cells or pots per cubic inch of cavity volume (n = 10 observations per component).

2.6. Statistical Analyses

Descriptive statistics were used to calculate means and standard deviations. Within each group, we assessed key assumptions for parametric testing, including normality (using the Shapiro–Wilk test and Q-Q plots), homoscedasticity (via scatter plots), and homogeneity of variance (using Levene’s test). If these assumptions were met, parametric tests were applied—for example, an independent t-test to compare the dimensions of queen cells with those of worker/drone cells. When assumptions were not met, non-parametric tests were used, such as the Kruskal–Wallis H test to compare nest densities across zones. If the p-value was significant (p ≤ 0.05), Dunn’s test was performed as a post hoc analysis. All statistical analyses were carried out using IBM SPSS Statistics version 26.0 and R software (R Core Team, 2022).

3. Results

3.1. Nest Distribution Patterns

The stingless bee species nested across a range of habitats, including agricultural areas, forest areas, rural areas with mixed vegetation, semi-urban areas, and urban environments. Nest density varied significantly among these habitats (Kruskal–Wallis H test: H = 63.26, df = 4, p < 0.001). The highest nest density was observed in rural areas with mixed vegetation and human settlement (2.80 ± 1.58 nests per 1000 m2), followed by semi-urban areas (1.90 ± 1.27 nests per 1000 m2), forest areas (1.50 ± 1.11 nests per 1000 m2), agricultural areas (0.67 ± 0.76 nests per 1000 m2), and urban areas (0.17 ± 0.38 nests per 1000 m2) (Figure 1). In some instances, multiple nests were found in close proximity, with the shortest distance between two nests being approximately 14.60 cm. Nest aggregations were also noted, and colony dispersion ranged from random to clumped patterns.

3.2. Nest Substrates

The stingless bee species selected a variety of substrates for nest construction, including tree trunks, walls, poles, rock crevices, and agricultural ridges (Table 1). Tree trunks (52.13% of occurrences) and walls (42.18%) were the most commonly used substrates for nesting. Nesting trees included Albizia lebbeck (L.) Benth., Borassus flabellifer L., Butea monosperma (Lam.) Taub., Eucalyptus tereticornis, Ficus benghalensis L., Ficus religiosa L., Holoptelea integrifolia (Roxb.) Planch., Madhuca longifolia (J. Konig) J. F. Macbr., Phoenix sylvestris (L.) Roxb., Syzygium cumini (L.) Skeels., and Tectona grandis (L. f.). Among these, Butea monosperma was the most frequently used (31.82% of tree-hosting nests), followed by Tectona grandis (22.73%), Ficus benghalensis, and Ficus religiosa (Table S1). Most nest-bearing branches were living (90%). The diameter at breast height (DBH) of nest-bearing trees ranged from 0.32 to 2.44 m (with an average of 0.60 ± 0.78 m), while the diameter near the nest site ranged from 0.29 to 2.37 m (with a mean of 0.54 ± 0.72 m). The bees also nested in various types of walls (Table S1), with mud walls being the most common (29.21%), followed by mud with stones (22.47%), mud with bricks (17.98%), and cement with bricks (16.85%). The thickness of the nest-bearing walls ranged from 0.20 to 0.46 m, with an average of 0.32 ± 0.10 m.

3.3. External Nest Characteristics

The elevation of nests from ground level ranged from 0 to 13.46 m, with the majority located below 2 m (Table 2). Nests at higher elevations were relatively rare. Nest entrances were oriented in all cardinal and intercardinal directions, with most facing north (18.48%) and northeast (17.54%), while a few faced south (4.27%) (Table 2). Approximately 35.07% of nests featured external tunnels (Figure 2), which were more commonly found in tree-trunk nests (58.18%) than in those built in walls or on poles. The length of these external tunnels ranged from 13 to 84 mm. Nest entrance openings varied in shape, including circular, oval, slit-like, and irregular forms, with circular outlines being the most common. The length of the longest axis of the entrance openings ranged from 6 to 17 mm, with a mean of 10.50 ± 2.94 mm. For circular entrances, the mean diameter was 8.12 ± 1.02 mm.

3.4. Internal Nest Characteristics

The internal tunnel length of wild nests ranged from 93 to 287 mm, with a mean of 177.20 ± 57.62 mm (Table 3). The internal cavities varied in shape—spherical, ellipsoid, cylindrical, or occasionally irregular. Cavity lengths (measured along the longest axis) ranged from 136 to 432 mm, with a mean of 198.31 ± 86.36 mm, while cavity widths (shortest axis) ranged from 124 to 181 mm, averaging 142.73 ± 17.28 mm. Each nest featured a brood zone surrounded by food storage areas. Supporting elements were sometimes present. Typically, brood cells were located centrally within the cavity, forming a single mass. Pollen and honey pots were arranged around the brood zone, usually in several small clusters (Figure 3). Brood cells for workers and drones were similar in shape, size, and colour, whereas queen cells were significantly larger (length: t = 14.74, df = 58, p < 0.001; width: t = 13.14, df = 58, p < 0.001) (Figure 4). The brood cells were ellipsoid and light brown, with a mean length of 2.86 ± 0.11 mm and a width of 1.95 ± 0.08 mm. The density of brood cells was highest among all components, averaging 60.20 ± 12.85 cells per cubic inch. This density differed significantly among brood cells, pollen pots, and honey pots (Kruskal–Wallis H test: H = 25.71, df = 2, p < 0.001). Pollen pots were dark brown and varied in shape from ellipsoidal to polygonal. They measured 5.94 ± 0.63 mm in length and 4.92 ± 0.48 mm in width, with a density of 16.20 ± 2.27 per cubic inch. Honey pots were also dark brown, ranging from ellipsoidal to polygonal in shape, and sometimes had dome-shaped tops. Their mean length was 6.87 ± 0.52 mm and width 5.70 ± 0.44 mm, with a density of 9.30 ± 1.68 per cubic inch. Structural support elements such as involucra and pillars (narrow strands) were observed within the nests (Figure 5). The involucra were flat and broad near the brood cells (lower region), tapering to narrow, cylindrical forms at the upper attachment point. The pillars were short, slender, cylindrical, and occasionally branched.

4. Discussion

4.1. Nest Distribution Patterns

The stingless bee species were found inhabiting a wide range of environments, including forested regions, agricultural lands, rural zones with mixed vegetation, semi-urban, and urban areas. Their wide ecological distribution highlights their adaptability, but also exposes them to a range of anthropogenic pressures, including habitat loss, pesticide exposure, monoculture farming, and urban expansion. Assuring the long-term survival of stingless bees requires targeted conservation strategies that integrate ecological, agricultural, and socio-economic dimensions, including habitat conservation and restoration, regulation of pesticide use, and reducing disturbances. The resilience of stingless bees in diverse habitats has also been documented for other stingless bee species, such as Tetragonisca angustula Latreille [37], Tetragonula laeviceps Smith [38], and Trigona spinipes Fabricius [37]. The nesting distribution of stingless bee species across various habitat types revealed significant variation in colony density. Notably, the highest nest density was observed in rural areas characterised by a mosaic of natural vegetation and human settlements and the lowest in urban areas with very low vegetation. Several studies (e.g., Eltz et al. [26]; Kiatoko et al. [39]) have established that colony density is generally higher in areas with dense vegetation compared to degraded habitats. However, our findings showed that nest density was highest in rural areas with mixed vegetation, surpassing even that of forested areas. The observed variation in nest density according to landscapes underscores the strong influence of habitat quality on stingless bee populations. Dense, mixed vegetation provides floral resources critical for colony establishment and survival. Conversely, urban areas are characterised by habitat fragmentation, reduced floral resources, and a high level of disturbance, leading to population decline. These findings emphasise the need for habitat-based conservation strategies, including the preservation of mixed vegetation patches, agroforestry systems, and hedgerows. Protecting these landscapes from intensive land-use change will help maintain high nest densities. In an urban context, strategies should aim to enhance green cover and floral density through the development of community gardens, urban parks, roadside plantations, and rooftop gardens, utilising bee-friendly plant species. The nest distribution pattern of the stingless bee species was predominantly clumped. Both random and clumped nest dispersion patterns have been well documented in other stingless bee species (e.g., Hubbell & Johnson [40]). In our study, nest aggregations were also occasionally observed. Similar nest aggregation behaviour has been reported in other stingless bee species, such as Trigona aff. cupira Smith [41] and Trigona collina Smith [42]. Such aggregations may result from limited dispersal distances during swarming, a high availability of suitable nesting sites within a substrate, or an abundance of local resources.

4.2. Nest Substrates

The nesting substrate preferences of the stingless bee species revealed a high degree of adaptability, with colonies established across a range of natural and anthropogenic structures, including tree trunks, walls, poles, rock crevices, and agricultural ridges. Among these, tree trunks and walls were the most frequently selected substrates, suggesting that both natural habitats and semi-modified environments play critical roles in sustaining their populations. From a conservative perspective, safeguarding natural substrates (e.g., tree trunks via integrating tree planting into reforestation and agroforestry programmes) and simultaneously promoting artificial nesting options in human-dominated landscapes will ensure long-term nesting availability. As a nesting substrate for stingless bees, several researchers have noted the use of tree cavities [43,44] and wall cavities [29,36,45]. Nest substrate selection for stingless bees may depend on the availability of nesting places, which in turn are related to local land use patterns. A variety of tree species supported nest establishment, with Butea monosperma, Tectona grandis, Ficus benghalensis, and Ficus religiosa being the most commonly utilised hosts. This suggests that these tree species provide favourable structural features, such as appropriate cavity sizes, bark texture, and microclimatic conditions, that are conducive to nesting. However, the selection of tree species as a substrate for stingless bees varies across regions and stingless bee species [23,46]. The tree trunks hosting the nests were predominantly living. This observation aligns with findings from other studies (e.g., Vossler [43]; Macedo et al. [46]). Living substrates offer a more durable structure and safer nesting sites for the bees. The selected trunks were medium to large in size (dbh: 0.32 to 2.44 m), offering sufficient space and stability for nest establishment. Similar preferences for host trees have also been reported for other stingless bee species by Kajobe [32]. In human-modified environments, stingless bees often utilised earthen walls, particularly those made of mud, mud mixed with stones, or mud combined with bricks. Basanna and Rajanand [35] reported a predominance of stone walls as nesting substrates for stingless bee species. Such wall types are likely more common in rural areas and may offer more suitable conditions for nesting.

4.3. External Nest Characteristics

Nests were found at elevations ranging from ground level up to 13.46 m, although the majority were located below 2 m. This behaviour underscores the importance of conserving near-ground vegetation, which may facilitate easy foraging, access to floral resources, and easy nest maintenance. Most stingless bees prefer to construct their nests at lower elevations [46]; however, higher nest elevations have been observed in some species, such as Melipona bacandei Spinola and Melipona nebulata Smith [32]. Nest entrances were oriented in all cardinal and intercardinal directions, with a higher frequency towards the north and northeast, and the lowest towards the south. A predominance of north-facing nest entrances has also been reported for other Indian stingless bee species (e.g., Tetragonula iridipennis [47]). This directional preference may reflect behavioural adaptations to optimise microclimatic conditions, such as temperature and light exposure, at the nest entrance. A considerable number of nests exhibited external tunnels, which were more frequently observed in tree-trunk nests than in those built within walls or on poles. The presence of external tunnels has also been reported for other stingless bee species by various researchers (e.g., Roopa et al. [48]; Miharja et al. [49]). These tunnels may offer protection against environmental factors (particularly rainfall) and potential predators. In Tetragonula pagdeni, the external tunnel was short to medium in length, ranging from 13 to 84 mm. Tunnel length varies between species and also depends on the nesting substrate. Similar tunnel lengths have been reported for some stingless bees (e.g., Tetragonula laeviceps [49]), while shorter tubes have been documented in species such as Trigona gribodei Margretti [50], and longer tubes in others, such as Lepidotrigona terminata Smith [49]. The entrance openings varied in shape (e.g., circular, oval, slit-like, or irregular), with circular and oval openings being the most common. The circular and oval shape of the nest opening may make it easier for foragers to exit and enter the nests. Entrance size also varied, with the longest axis measuring 6–17 mm. These entrance traits, including shape and size, may influence colony ventilation, predator exclusion, and internal environmental stability.

4.4. Internal Nest Characteristics

The nests featured an internal tunnel connecting the nest cavity to the exterior of the substrate, with lengths ranging from 93 to 287 mm. This observation is consistent with findings from other studies on stingless bees (e.g., Gajanan et al. [45]; Danaraddi et al. [29]). The length of the internal tunnel may vary depending on the cavity’s position within the substrate. The nest volume (here, cavity dimensions) also varied, indicating flexibility in nest construction within available substrates. Nest volume is influenced by various factors, including the age of the colony, the available space within the substrate, resource availability, environmental conditions, and the bee species involved [51]. Internally, nest architecture was consistently organised with a brood zone surrounded by food storage zones. A similar organisation has also been reported for this stingless bee species [11], as well as for other stingless bee species (e.g., Meliponula (Axestotrigona) ferruginea Cockerell [27]; Tetragonula iridipennis [29,45]). This spatial arrangement likely facilitates efficient colony functioning, allowing ease of access to food reserves while maintaining optimal brood rearing conditions. Brood cells were ellipsoid, light brown, and tightly clustered, while food pots (for honey and pollen) were light to dark brown, highly variable in shape, and less densely arranged. This pattern is common in many other stingless bees (e.g., Meliponula bocandei Spinola [25]; Tetragonula iridipennis [29]). However, the dome-shaped upper portions of some pollen pots observed in this stingless bee species may be characteristic of the species. The higher density of brood cells suggests the use of space-efficient brood rearing strategies. Nest supporting structures, such as involucra and pillars, were present in all nests and have also been reported in many other stingless bee species (e.g., Meliponula bocandei [25]; Meliponula (Axestotrigona) ferruginea [27]), although their forms may vary by species. In Tetragonula pagdeni nests, the involucra were light to dark brown, thin, and flat, with the attachment point to the substrate often forming a narrow, cylindrical shape. The pillars were slender and cylindrical. These elements help anchor various nest components and contribute to overall structural stability. Therefore, to ensure long-term colony stability, management strategies should aim to minimise disturbances such as logging, pruning, or vibrations near nesting sites. Additionally, encouraging the retention of durable nest substrates (e.g., old trees and other hardy nest-hosting structures) can provide long-lasting nesting opportunities.

5. Conclusions

Tetragonula pagdeni occurred across a range of landscapes, with nest density highest in rural areas characterised by dense mixed vegetation and human settlements, and lowest in urban areas with sparse vegetation and high levels of anthropogenic disturbance. The stingless bee colonies were eusocial, perennial, and cavity-nesting. They nested in cavities within tree trunks, building walls, rock crevices, electric poles, and field ridges, with tree trunks and walls being most common. Wild nests were predominantly found at low elevations, typically within 2 m of the ground. Nest entrances varied in shape (circular, oval, slit-like, or irregular), averaged 10.50 ± 2.94 mm across the longest axis, and faced various directions. Internally, brood zones were surrounded by honey and pollen pots, and supported by involucra and pillars. Brood cells were light brown, oval, and compactly clustered; worker and drone cells were similar, while queen cells were larger. Honey and pollen pots ranged from light to dark brown and varied in shape. Involucra were thin, flat sheets; pillars were short, narrow, and thread-like. These observations enhance understanding of the species’ distribution, nesting habits, and nest architecture, aiding its conservation and sustainable use. Collectively, these observations indicated that stingless bees exhibit a high degree of plasticity in nesting behaviour, which likely contributes to their ecological success and informs the importance of conserving both natural and semi-natural habitats to support their populations.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/conservation5040063/s1, Table S1. Information about tree trunks and walls utilised as nesting substrates by Tetragonula pagdeni in West Bengal, India.

Author Contributions

Conceptualization: U.L. and P.K.; methodology: U.L.; formal analysis: U.L. and P.K.; investigation: U.L.; data curation: U.L.; writing—original draft: U.L.; writing—review and editing: P.K.; visualization: U.L.; supervision: P.K.; All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data were available within the article and supplementary files.

Acknowledgments

The authors sincerely thank the authorities of Rampurhat College and Vidyasagar University, West Bengal, India, for their support. They are grateful to Sourabh Bisui (Department of Botany and Forestry, Vidyasagar University) and Suman Kumar De (Department of Botany and Forestry, Vidyasagar University) for their assistance in data collection. Special thanks are also extended to Shashidhar Virakamath (Department of Entomology, University of Agricultural Sciences, Bengaluru, Karnataka), who helped us with the identification of the stingless bee species.

Conflicts of Interest

The authors declare that they have no conflicts of interest to disclose.

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Figure 1. Nest densities of stingless bees (Tetragonula pagdeni) in different vegetation zones. Different letters indicate statistically significant differences (Kruskal–Wallis H test and Dunn’s post hoc test at the 0.05 level).
Figure 1. Nest densities of stingless bees (Tetragonula pagdeni) in different vegetation zones. Different letters indicate statistically significant differences (Kruskal–Wallis H test and Dunn’s post hoc test at the 0.05 level).
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Figure 2. Nests of stingless bees (Tetragonula pagdeni). (A) Nest with an external tunnel and (B) nest without an external tunnel.
Figure 2. Nests of stingless bees (Tetragonula pagdeni). (A) Nest with an external tunnel and (B) nest without an external tunnel.
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Figure 3. Internal structures of nests of stingless bees (Tetragonula pagdeni). (A) Early stage of colony growth, and (B) fully grown colony.
Figure 3. Internal structures of nests of stingless bees (Tetragonula pagdeni). (A) Early stage of colony growth, and (B) fully grown colony.
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Figure 4. Brood cells and food pots of the nest of stingless bees (Tetragonula pagdeni). (A) Brood cells for workers and drones, (B) developing queen cells (showing by yellow arrows), (C) mature queen cells (showing by yellow arrows), (D) dark brown honey pots, (E) light brown honey pots, (F) a developing pollen pot, and (G) showing intermingled honey and pollen pots (h—honey pot, p—pollen pot). Scale bars = 10 mm.
Figure 4. Brood cells and food pots of the nest of stingless bees (Tetragonula pagdeni). (A) Brood cells for workers and drones, (B) developing queen cells (showing by yellow arrows), (C) mature queen cells (showing by yellow arrows), (D) dark brown honey pots, (E) light brown honey pots, (F) a developing pollen pot, and (G) showing intermingled honey and pollen pots (h—honey pot, p—pollen pot). Scale bars = 10 mm.
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Figure 5. Nest-supporting structures of stingless bees (Tetragonula pagdeni). (A–C) Involuca. (A) Dark brown involucre, (B) light brown involucre, (C) involucre with thin, flat attachment region. (D–F) Pillars. (D,E) Light brown pillars, (F) dark brown pillars. Scale bars = 10 mm.
Figure 5. Nest-supporting structures of stingless bees (Tetragonula pagdeni). (A–C) Involuca. (A) Dark brown involucre, (B) light brown involucre, (C) involucre with thin, flat attachment region. (D–F) Pillars. (D,E) Light brown pillars, (F) dark brown pillars. Scale bars = 10 mm.
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Table 1. Nesting substrates and occurrence of nests of Tetragonula pagdeni in West Bengal, India.
Table 1. Nesting substrates and occurrence of nests of Tetragonula pagdeni in West Bengal, India.
SubstratesOccurrence of Nests (%)
Agricultural AreasForest AreasRural AreasSemi-Urban AreasUrban AreasOverall
Tree trunks8586.6740.4731.584052.13
Walls0058.3364.916042.18
Rock crevices013.330002.84
Agricultural ridges1500001.42
Poles001.193.5101.42
Table 2. External characteristics of nests of Tetragonula pagdeni in West Bengal, India.
Table 2. External characteristics of nests of Tetragonula pagdeni in West Bengal, India.
ParametersAvailable Information
Elevation from ground level
  • Height from ground level (m)
Range: 0–13.46; 2.81 ± 3.17 (mean ± SD)
  • Occurrence of nests at different height classes (%)
≤2 m (59.24%), >2–4 m (24.17%), >4–6 m (7.11%), >6–8 m (5.21%), >8–10 m (3.32%), >10 m (0.95%)
Orientation of nest entranceEast (13.74%), west (13.27%), north (18.48%), south (4.27%), northeast (17.54%), northwest (11.37%), southeast (10.90%), southwest (10.43%)
External tunnel
  • Occurrence (%)
Tree trunks (58.18%), walls (8.99%), rock crevices (16.67%), agricultural ridges (33.33%), pole (0%); overall (35.07%)
  • Length (mm)
Range: 13–84; 64.21 ± 14.61 (mean ± SD)
Nest entrance
  • Shape of outline
Circular (54.98%), oval (39.34%), slit-like (4.27%), irregular (1.42%)
  • Size (length of longest axis in mm)
Range: 6–17; 10.50 ± 2.94 (mean ± SD)
  • Size (diameter of circular entrances in mm)
Range: 6–10; 8.12 ± 1.02 (mean ± SD)
SD—standard deviation.
Table 3. Internal characteristics of nests of Tetragonula pagdeni in West Bengal, India.
Table 3. Internal characteristics of nests of Tetragonula pagdeni in West Bengal, India.
ParametersAvailable Information
Internal tunnel length (in mm, n = 10)Range: 93–287; 177.20 ± 57.62 (mean ± SD)
Cavity dimensions
  • Length (in mm, n = 10)
Range: 136–432; 198.31 ± 86.36 (mean ± SD)
  • Width (in mm, n = 10)
Range: 124–181; 142.73 ± 17.28 (mean ± SD)
Brood cells for workers & drones
  • Colour
Light brown
  • Length (in mm, n = 50)
Range: 2.50–3.00; 2.86 ± 0.23 (mean ± SD)
  • Width (in mm, n = 50)
Range: 1.50–2.00; 1.95 ± 0.15 (mean ± SD)
  • Density (cells/inch3, n = 10)
Range: 48–71; 59.20 ± 7.43 (mean ± SD)
Brood cells for queens
  • Colour
Light brown
  • Length (in mm, n = 10)
Range: 3.50–4.50; 4.10 ± 0.32 (mean ± SD)
  • Width (in mm, n = 10)
Range: 2.50–3.50; 2.90 ± 0.39 (mean ± SD)
Honey pots
  • Colour
Light brown, dark brown
  • Length (in mm, n = 50)
Range: 6.00–7.50; 6.87 ± 0.52 (mean ± SD)
  • Width (in mm, n = 50)
Range: 5.00–6.50; 5.70 ± 0.44 (mean ± SD)
  • Density (cells/inch3, n = 10)
Range: 6–12; 9.00 ± 1.83 (mean ± SD)
Pollen pots
  • Colour
Light brown, dark brown
  • Length (in mm, n = 50)
Range: 5.00–6.50; 5.94 ± 0.63 (mean ± SD)
  • Width (in mm, n = 50)
Range: 4.00–5.50; 4.92 ± 0.48 (mean ± SD)
  • Density (cells/inch3, n = 10)
Range: 12–20; 16.20 ± 2.66 (mean ± SD)
Supporting elements
  • Involucra
Light brown and dark brown, flat, broad, attachment portion with substrate mostly narrow and cylindrical, sometimes flat
  • Pillars
Light brown and dark brown, flat, broad, attachment portion with substrate mostly narrow and cylindrical, sometimes flat
SD—standard deviation.
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Layek, U.; Karmakar, P. Distribution Patterns, Nesting Ecology and Nest Characteristics of the Stingless Bees (Tetragonula pagdeni Schwarz) in West Bengal, India. Conservation 2025, 5, 63. https://doi.org/10.3390/conservation5040063

AMA Style

Layek U, Karmakar P. Distribution Patterns, Nesting Ecology and Nest Characteristics of the Stingless Bees (Tetragonula pagdeni Schwarz) in West Bengal, India. Conservation. 2025; 5(4):63. https://doi.org/10.3390/conservation5040063

Chicago/Turabian Style

Layek, Ujjwal, and Prakash Karmakar. 2025. "Distribution Patterns, Nesting Ecology and Nest Characteristics of the Stingless Bees (Tetragonula pagdeni Schwarz) in West Bengal, India" Conservation 5, no. 4: 63. https://doi.org/10.3390/conservation5040063

APA Style

Layek, U., & Karmakar, P. (2025). Distribution Patterns, Nesting Ecology and Nest Characteristics of the Stingless Bees (Tetragonula pagdeni Schwarz) in West Bengal, India. Conservation, 5(4), 63. https://doi.org/10.3390/conservation5040063

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