Nesting behavior and habitats of the stingless bee Trigona iridipennis Smith in Kerala

Table of contents

Table of figures

Table of tables

List of abbreviations

Abstract

1. Introduction

2. Hypothesis

3. Materials and Methods
3.1 Study area
3.2 Study design and data collection
3.3 Statistical analysis

4. Results
4.1 Nest architecture and characteristics
4.2 Anthropogenic habitats
4.3 Domesticated habitats
4.4 Different types of nests

5. Discussion

6. Conclusions

Acknowledgements

References

Table of figures

Figure 1. Mean monthly rainfall (mm), maximum and minimum temperatures (°C) in Kerala, India (1871-2005; Krishnakumar et al., 2009)

Figure 2. Map of Kerala showing various sample collection points marked as a star symbol during the study (Authors own image)

Figure 3. Stingless bee a) worker foraging on euphorbia flower; b) drone (top) and worker (bottom); c) brood with queen cell; d) entrance tube with fresh resin at the tip; e) food pots (honey) and pollen pots intermingled (Authors own image)

Figure 4. Different types of bee nests a) hives placed on the stand; b) PVC pipe nest; c) earthen pot nest; d) nest in coconut shell; e) bamboo pole nest; f) earthen bowl nest exposed; g) log nest; h) nest in garden pot; i) two tier earthen bowl nest (Authors own image)

Figure 5. Various types of nests and nest entrance among stingless bees a) upward directional entrance tube; b), c) and d) entrance tube on stone walls; e) entrance tube on scooter engine ; f) exposed mud wall nest; g) guard bees near the entrance tube (Authors own image)

Figure 6. Schematic representation of stingless bees in differ habitats a) bamboo pole; b) wooden box; c) inside a tree cavity

Figure 7. Preference of farmers (n=15) for the cultivation of stingless bees in Kerala using different materials.

Table of tables

Table 1. Resin sources for Trigona iridipennis Smith in Kerala

Table 2. Internal structure of the nest of Trigona iridipennis Smith

Table 3. Trees harboring nests of Trigona iridipennis Smith in Kerala

Table 4. Site description of the selected locations (W1-W21) across Kerala, India for nesting behavioural study during 2011-2013.

List of abbreviations

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Nesting behavior and habitats of stingless bees ( Trigona iridipennis Smith) in Kerala: current status of knowledge

Prem Jose Vazhacharickal1* and Sajan Jose K2

* premjosev@gmail.com

1 Department of Biotechnology, Mar Augusthinose College, Ramapuram, Kerala, India-686576

2 Department of Zoology, St. Joseph’s College, Moolamattom, Kerala, India-685591

Abstract

Stingless bees are highly social insects which populated the tropical earth 65 million years ago longer than honey bees. They are limited to tropics and subtropics lacking venom apparatus and cannot sting. Impacts of anthropogenic influences on honey bees were already reported. Recent studies also showed that the nesting behaviour of Trigona iridipennis Smith in natural habitat also vary due to interaction, pheromones and environmental stimulus. A little is reported so far about the various natural and domesticated nesting of the Trigona iridipennis Smith in Kerala. Based on these back ground, our objectives of this study were to 1) to characterize the Meliponiculture 2) to identify the various natural habitats and domestication materials for nest construction and different types of nests used across Kerala. Various beekeeping methods preferred by farmers across Kerala for the cultivation of Trigona iridipennis Smith. Each nest has its own advantage and disadvantage. During the survey, the most preferred one’s were wooden box. Even then according to the easy availability and production cost different nests like earthen pot, bamboo nodes, coconut shell, PVC pipes etc were used. The most preferred natural nesting sites by Trigona iridipennis Smith were mud/stone walls in our study. Being a social insect, Trigona iridipennis Smith shows great diversity in nesting pattern in natural habitats as well as anthropogenic habitats. The shift towards anthropogenic habitats than natural ones may be due to destruction of natural habitats as well as the availability of manmade habitats.

Keywords: Trigona iridipennis Smith; Anthropogenic habitats; Entrance tube; Meliponiculture.

1. Introduction

Stingless bees are highly social (eusocial) insects which populated the tropical earth 65 million years ago longer than honey bees (Camargo and Pedro, 1992). They are limited to tropics and subtropics lacking venom apparatus and cannot sting. They have well developed mandibles using which they can bite and keep away intruders. Vestigial sting, presence of penicillum (a bunch of stiff setae on the outer apical margin of hind tibia), reduction and weakness of wing venation are the three major characters of stingless bees. The stingless bee found in Kerala is Trigona iridipennis Smith also called ‘dammer bees’ as they collect a kind of resin from plants to construct their nest. They are locally known as ‘Cherutheneecha’ in Malayalam has also called mosquito bees and are found all over India (Singh, 2013). The name Trigona refers to their triangular abdomen and ‘ iridipennis ’ refers to their iridescent wings. Stingless bees are small to medium sized with vestigial stings, shows social level of organization and pollinators of flowering plants in the tropics (Ramanujam et al., 1993; Heard, 1999; Amano et al., 2000; Raju et al., 2009). The Trigona iridipennis Smith is considered as highly eusocial bees living as perennial colonies. They belong to the family Apidae and subfamily Meliponinae capable of domesticating in hives can moved from places with non-stinging characteristics (Amano et al., 2000; Franck et al., 2004, Rasmussen, 2013).

Keeping of stingless bees is called Meliponiculture and Trigona iridipennis Smith are kept in India for centuries for the high medicinal value of honey as well as propolis and bee wax (Cortopassi-Laurino et al., 2006; Choudhari et al., 2012; Kumar et al., 2012; Andualem, 2013; Choudhari et al., 2013; Rasmussen, 2013; Virkar et al., 2014). The average of the honey ranges from 400-600 g per colony and fetch around 2000 INR (12 US$) per kilogram due to its less productivity as well as high demand from pharmaceutical sector (Kumar et al., 2012). Honey of the stingless bee, Trigona spp., is usually a highly praised apitherapeutic agent used as a panacea against dozens of ailments in Ethiopia. Among the most common uses of stingless bee honey are to treat stomach disturbance, cough, tonsillitis, sore throat, stomach and intestinal ulcers, cold, disease of the mouth, mucus membrane, and as a wound dressing due to its antimicrobial activity (Garedew, 2004; DeMera and Angert, 2004; Boorn et al., 2010).

Impact of anthropogenic influences on honey bees were already reported by Basavarajappa (2010). Recent studies also showed that the nesting behaviour of Trigona iridipennis Smith in natural habitat also vary due to interaction, pheromones and environmental stimulus (Basavarajappa, 2010; Pavithra et al., 2012). A little is reported so far about the various natural and domesticated nesting of the Trigona iridipennis Smith in Kerala.

According to Singh (2013) and Mohan and Devanesan (1999), the nest of Trigona iridipennis Smith consist of entrance, brood, food storage pots, resin dump, waste dump, pillars, connectives, involucrum, and batumen. Difference in the entrance depending on the species (Chinh et al., 2005; Bänziger et al., 2011; Pavithra et al., 2012; Danaraddi et al., 2012) as well as tree preference for building nest (Marisa and Salni, 2012). Worker bees secrete wax which are mixed with resin collected from various trees especially red wood, jackfruit, bread fruit forming a dark coloured sticky substance called cerumen (Nair and Nair, 2001; Nair, 2003; Marisa and Salni, 2012; Rasmussen, 2013; Singh, 2013). Usually the brood is in the form of cluster which contains larvae. Honey and pollen pots are larger than brood cells. The brood cells are oval in shape, arranged in clusters connected to each other by short pillars and connectives. The worker bees are a bit darker in colour with a mean body length of 4.07 mm. The queen have golden brown colour with a mean body length of 10.07 mm (Devanesan et al., 2009). Based on these back ground, our objectives of this study were to 1) to characterize the Meliponiculture 2) to identify the various natural habitats and domestication materials for nest construction and different types of nests used across Kerala.

2. Hypothesis

The current research work is based on the following hypothesis

1) The nesting behaviour and habitats of stingless bees in Kerala may vary across different locations

2) Farmers in Kerala grow stingless bees in conventional and non-conventional methods.

3. Materials and Methods

3.1 Study area

Kerala state covers an area of 38,863 km2 with a population density of 859 per km2 and spread across 14 districts. The climate is characterized by tropical wet and dry with average annual rainfall amounts to 2,817 ± 406 mm and mean annual temperature is 26.8°C (averages from 1871-2005; Krishnakumar et al., 2009). Maximum rainfall occurs from June to September mainly due to South West Monsoon and temperatures are highest in May and November (Figure 1).

3.2 Study design and data collection

Twenty five stingless bee samples were collected from twenty one locations in twelve districts across Kerala using information’s collected from various agricultural departments, farmers and beneficiaries (Figure 2). Few nests on wall and tree trunk were made exposed to learn the internal nest architecture. Hundred and twenty farmers engaged in Meliponiculture were interviewed and observed. A questionnaire was prepared and distributed among the farmers to learn their depth in Meliponiculture methods and techniques and to study the current status of Meliponiculture in Kerala. The plus and minus points of various Meliponiculture techniques were also mentioned.

3.3 Statistical analysis

The survey results were analyzed and descriptive statistics were done using SPSS 12.0 (SPSS Inc., an IBM Company, Chicago, USA) and graphs were generated using Sigma Plot 7 (Systat Software Inc., Chicago, USA).

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Figure 1. Mean monthly rainfall (mm), maximum and minimum temperatures (°C) in Kerala, India (1871-2005; Krishnakumar et al., 2009). Author’s own work.

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Figure 2. Map of Kerala showing various sample collection points marked as a star symbol during the study (Authors own image).

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Figure 3. Stingless bee a) worker foraging on euphorbia flower; b) drone (top) and worker (bottom); c) brood with queen cell; d) entrance tube with fresh resin at the tip; e) food pots (honey) and pollen pots intermingled (Authors own image).

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Figure 4. Different types of bee nests a) hives placed on the stand; b) PVC pipe nest; c) earthen pot nest; d) nest in coconut shell; e) bamboo pole nest; f) earthen bowl nest exposed; g) log nest; h) nest in garden pot; i) two tier earthen bowl nest (Authors own image).

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Figure 5. Various types of nests and nest entrance among stingless bees a) upward directional entrance tube; b), c) and d) entrance tube on stone walls; e) entrance tube on scooter engine ; f) exposed mud wall nest; g) guard bees near the entrance tube (Authors own image).

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Figure 6. Schematic representation of stingless bees in differ habitats a) bamboo pole; b) wooden box; c) inside a tree cavity.

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Figure 7. Preference of farmers (n=15) for the cultivation of stingless bees in Kerala using different materials. Authors own work.

4. Results

4.1 Nest architecture and characteristics

The nest is the central place from which stingless bees mate, forage and pass through life stages. Nests are immobile fixtures and potentially long live (Michener, 1974; Roubik, 1989). Wall cavities and tree cavities are the major nesting sites for Trigona iridipennis Smith. They also make their nests in switch boards, telephone posts, discarded pipes etc. Though rare they were also found construct their nest on lorry cabin and also in scooter engine box. One colony even made their nest in a rain coat which was hanged in the car-porch in the off season. They are highly anthropophilous and more active in vicinity of human surroundings. A conspicuous entrance tube is found in front of the nest (Figure 3).

4.1.1 Entrance tube

The stingless bee nest is always characterized by a nest cavity, typically provided with a very narrow opening facilitating defence (Kolmes and Sommeijer, 1992). The simplest stingless bee nest entrance protrudes slightly from the base of the entrance hole. Nest entrance is related to defence and foraging (Biesmeijer et al., 2005). It is made up of cerumen, a mixture of wax and resin. In addition to wax and resin foreign materials like grease, smoke particles, fibres, mud, dust particles etc may be seen on the entrance tube. In few colonies workers found to deposit particles of “Oil Mace” on the entrance tube. The length and width of the tube vary according to the strength of the colony and the location of the nest. There is no direct relation between the length of the tube and the age of the colony. The length of the entrance tube varies from 1.2 to 11 cm. The diameter of the entrance tube ranges from 0.7 to 2.4 cm. The wall of the tube is thin and fragile. The entrance tubes are usually directed downwards, but at our surprise one of the entrance tube was found directed upwards. The number of guard bees at the entrance varies according to the strength of the colony.

Entrance tube were absent in some colonies. The number of guard bees at entrance varies from two to sixteen. The shape of the entrance may be slit like, circular, oval or funnel like. Around the entrance tube resin deposit is found in some colonies. This deposit may be in definite patterns like concentric rings or may be irregular. The shape, size and direction of the entrance tube vary according to the nest site conditions. Outer surface of the entrance tube is usually rough and the inner surface is smooth. The recently built apical part of the entrance tube is softer and usually slightly sticky. Usually a single entrance is present at the tip of the entrance tube. Though rare in some cases more than one entrance is seen on the same entrance tube. In some nests two separate functional entrance tube were observed. Instead of opening directly into the nest the entrance tube opens into the nest through some tunnels called internal tunnel.

4.1.2 Internal tunnel

Internal tunnel are usually branched and are made of soft cerumen. The long internal tunnel helps the stingless bees to effectively defend the colony against intruders.

4.1.3 Resin dumb

The nests of stingless bees are made up of cerumen, a mixture of resin and wax which remains soft for an extended time and is more pliable than beeswax (Wille, 1983; Hepburn and Kurstjens, 1984). In addition to being used for constructing nest forms, cerumen may also be used for repairing nest damage. The resin is collected from resinous plants like Jack fruit, mango tree etc. and wax is secreted by the young worker bees. The chemistry of propolis depends on the diversity of plants from which the bees collect it (Pereira, 2003).

The resin is deposited in the nest at different places especially near the entrance. Guard bees use this resin to prevent invaders (Wille, 1983). In addition to being used for constructing nest forms, cerumen may be taken to make an emergency repair of natural enemy damage (Roubik, 2006). Cerumen is normally made freshly to construct brood cells, involucrum, nest entrance tubes, or storage pots. The wax is taken from a pure wax deposit and mixes it with fresh resin taken from a resin deposit. These may be in several positions near the nest entrance and brood cells; workers mix the materials with their mandibles (Sakagami, 1982). Melipona are keenly interested in returning to a damaged nest and collect resin from resin deposits, and also cerumen and honey, as do many stingless bee genera (Roubik, 2006). Inside the nest resin deposit can be seen at different places especially at the entrance. Three to eight deposits were seen in different nests. Nests with weak wall contain more resin deposit. In pot nest covered with cloth worker bees deposit large quantity of resin.

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