Month-wise floral calendar of Tetragonula iridipennis (Smith, 1854) at Agriculture Research Station,Gangavathi,Karnataka, India

Introduction

Stingless bees (Hymenoptera: Apidae; tribe Meliponini) are the most species-rich group of social bees and are ecologically important pollinators across tropical and subtropical ecosystems worldwide (Engel et al., 2023; Wille, 1983) [1,2] . In peninsular India, Tetragonula iridipennis (Smith, 1854), commonly known as the Dammar bee, is the most widely distributed and commercially reared meliponine species. Meliponiculture has gained considerable momentum in Karnataka, Tamil Nadu and Kerala owing to the high medicinal and nutraceutical value of its honey (Rasmussen, 2013; Sabatina et al., 2024; Slaa et al., 2006) [3,4,5] . The foraging behaviour of T. iridipennis is governed by the availability, diversity and phenological succession of floral resources within its effective foraging radius, typically constrained to 500 m in small-bodied meliponines (Bisui et al., 2019; Layek et al., 2018; Layek et al., 2024) [6,7,8] . A detailed knowledge of the local bee pasture is therefore a prerequisite for productive meliponiculture and for scheduling colony management interventions such as supplementary feeding, colony splitting and honey extraction (Sabatina et al., 2024; Sabatina et al., 2025; Sheetal et al., 2025) [4,9,10] . Pollen and floral calendars are tabular or graphical representations integrating field-observed flowering phenology to depict the temporal availability of pollen and nectar for bees across the annual cycle. Such calendars have been employed in apicultural research to identify honey flow and dearth periods, to guide migratory beekeeping and to plan bee pasture improvement (Nalini et al., 2024; Rani et al., 2026; Waykar et al., 2015) [11,12,13] . However, species-specific calendars for T. iridipennis remain sparse for the semi-arid agroecological conditions of northern Karnataka (Moulya et al., 2023; Sheetal et al., 2025; Vamshikrishna et al., 2021) [14,10,15] . The Agricultural Research Station (ARS), Gangavathi, maintained by the University of Agricultural Sciences, Raichur, hosts an active meliponiculture programme, making it an ideal site for systematic bee pasture documentation. The present study was designed to (1) enumerate and identify plant species visited by T. iridipennis foragers within the 500 m apiary radius; (2) characterise seasonal foraging patterns and construct a month-wise pollen and floral calendar; and (3) delineate honey flow and dearth periods to support evidence-based colony management.

Materials and methods

Study site: The study was conducted at Agriculture Research Station (ARS), Gangavathi (15°25'N, 76°31'E; ~385 m asl), Koppal district, Karnataka, India. The site experiences a semi-arid climate with mean annual rainfall of approximately 580-620 mm distributed across two monsoon seasons. Temperatures range from 15-22 °C in December-January to 36-42 °C in April-May. The apiary housed colonies of T. iridipennis in traditional clay pots and wooden log hives. The landscape within a 500 m radius comprised experimental crop plots, avenue plantations, kitchen gardens, ornamental beds and patches of scrub vegetation.

Study period and seasonal coverage

Floral resource surveys and corbicular pollen sampling were carried out continuously from 1 November 2025 to 31 March 2026 (151 days), spanning the cool-dry phase (November 2025-January 2026) and the transitional phase (February-March 2026). Field survey design: A roving observation survey was conducted within a 500 m radius of the apiary (Bisui et al., 2019; Layek et al., 2024) [6,8] . Surveys were undertaken twice per week, yielding approximately 43 survey events. Observations were carried out on rainfree days with calm to light wind conditions, between 08:00 and 17:00 h, with concentrated effort during the two documented foraging peaks of T. iridipennis: 10:00-12:00 h and 14:00-16:00 h (Bharath et al., 2020) [16] . A plant species was scored as a bee forage plant only when at least three foragers were observed simultaneously visiting its flowers within a 10-minute observation window (Waykar et al., 2015) [13] .

Plant identification

All plants visited by foragers were identified to species level by consulting a resident botanist and cross-referencing regional floristic literature, authenticated pictorial field guides and online databases including the Botanical Survey of India and Digital Flora of Karnataka. Nomenclature follows the World (Flora Online) [17] . [18,13] . Honey flow and dearth periods were delineated based on monthly peak-bloom species count (Kumar et al., 2013; Waykar et al., 2015) [19,13] .

Floral calendar construction

Results

A total of 108 plant species distributed across 48 families were documented as bee pasture plants of T. iridipennis within the 500 m foraging radius at ARS, Gangavathi (Table 1

Discussion

The documentation of 108 plant species across 48 families as bee pasture resources of T. iridipennis at ARS, Gangavathi highlights the remarkable floral breadth exploited by this generalist forager in a semiarid agro-ecosystem. This species richness is comparable to figures from similar surveys for Apis species in subtropical India, where studies typically enumerate 60-130 bee forage species (Rani et al., 2026; Waykar et al., 2015) [12,13] and for stingless bees at other Karnataka sites (Moulya et al., 2023; Sheetal et al., 2025) [14,10] . The higherthan-expected richness at a semi-arid site is attributable to the mosaic land use of ARS, which juxtaposes experimental crop plots, plantation rows, ornamental gardens and natural scrub, each contributing complementary bloom windows (Bisui et al., 2021; Ponnuchamy et al., 2014) [20,21] . The dominance of Fabaceae is consistent with its ecological prominence in tropical and subtropical apicultural landscapes across India (Moulya et al., 2023; Rani et al., 2026; Sheetal et al., 2025) [14,12,10] . This family's diverse growth forms from large forest trees (Pongamia pinnata, Delonix regia) to annual crops (Cajanus cajan, Vigna spp.) ensure representation across habitats and seasons. The consistent foraging preference for Fabaceous species may reflect the protein-rich pollen of this family, which supports colony development and brood production in meliponines (Brodschneider et al., 2010; Slaa et al., 2006) [22,5] . The major honey flow period (October-February) has direct practical significance for meliponiculture management. Colony operations including expansion to new boxes, colony splitting and primary honey harvest should be scheduled within this window (Keller et al., 2005) [23] . The critical dearth period (mid-May to mid-August) demands proactive management: supplementary feeding should be initiated by mid-April (Brodschneider et al., 2010; Keller et al., 2005) [22,23] . The sixteen year-round bloomers particularly Muntingia calabura, Calotropis gigantea, Lantana camara, Hibiscus rosa-sinensis and Musa paradisiaca function as keystone forage anchors sustaining baseline colony survival during climatically unfavourable periods (Bharath et al., 2020; Sabatina et al., 2025) [16,9] . The comparative analysis with studies in Maharashtra (Waykar et al., 2015) [13] , Karnataka (Moulya et [14,11,10] and Uttar Pradesh (Rani et al., 2026) [12] reveals shared dominant families (Fabaceae, Asteraceae, Apocynaceae) pointing to pan-Indian patterns in stingless bee forage preferences (Ponnuchamy et al., 2014) [21] . The stronger contribution of Arecaceae (Cocos nucifera, Phoenix sylvestris, Roystonea regia) at the semi-arid Gangavathi site reflects the greater prevalence of palm cultivation in peninsular Karnataka (Vijayakumar et al., 2016) [24] . The 151-day survey window covers the primary foraging season. Future work should extend to a full twelve months, particularly covering the monsoon months (July-September) when crop-related floral resources bloom and when the actual foraging response of T. iridipennis to rain-interrupted conditions can be directly quantified. Palynological analysis of corbicular pollen loads would further refine species-specific forage preferences and enable construction of a quantitative seasonal pollen spectrum (Bisui et al., 2021; Ponnuchamy et al., 2014) [20,21] .

Conclusion

This study presents the first systematic month-wise pollen and floral calendar for Tetragonula iridipennis in the semi-arid agro-ecosystem of northern Karnataka, documenting 108 plant species across 48 fam-ilies as bee pasture resources at ARS, Gangavathi. Fabaceae (15.74%), Asteraceae (9.26%) and Solanaceae/Apocynaceae (4.63% each) dominate the bee pasture flora. Sixteen keystone year-round bloomers ensure perennial forage continuity. The major honey flow period spans October-February and a secondary flow occurs in March-April, representing the optimal windows for colony expansion and honey harvest. The critical dearth period (mid-May to mid-August) requires proactive supplementary feeding. Augmentation of bee pasture with year-round bloomers (Muntingia calabura, Callistemon lanceolatus, Hamelia patens, Turnera ulmifolia) within 200-300 m of apiaries is recommended to buffer dearth periods and enhance forage continuity.

Moringaceae

Acknowledgement

AcknowledgementsThe authors express sincere gratitude to the Centre of Excellence in Apiculture, CoA, Gangavathi funded by Dept. of IT and BT under VGST program, GoK for providing all the necessary facilities to conduct experiment. Authors are also grateful to the Department of Apiculture, University of Agricultural Sciences, GKVK, Bangalore for assistance in pollen identification studies. The authors declare no conflict of interest.

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30. How to cite this article: Manjunatha M, Yaligar R, Badariprasad P, Sreenivas A, Barkeer S. Month-wise floral calendar of Tetragonula iridipennis (Smith, 1854) at Agriculture Research Station, Gangavathi, Karnataka, India. International Journal of Advanced Biochemistry Research. 2026;SP 10(9):1465-1471. doi: https://www.doi.org/10.33545/26174693.2026.v10.i9Sr.1002