Nest Architecture and Nesting Behaviour of the Large Carpenter Bee in Tamil Nadu, India

Introduction

Large carpenter bees belong to the family Apidae, tribe Xylocopini, and genus Xylocopa and they play a vital role in pollination of both cultivated and wild flora. Female bees gather pollen and nectar to provision their young ones. They exhibit specialized nesting behavior, constructing nests in wooden structures, hollow stems, and pithy stems of Calotropis procera (Hannan et al., 2012) [3] , as well as bamboo culms (Hongjamrassilp and Warrit, 2014) [7] . However, members of the subgenus Proxylocopa and Xylocopa xinjiangensis build their nests in soil (He and Zhu, 2018) [6] . Xylocopa ordinaria Smith relies on the availability of suitable wood for nesting substrates rather than taxonomic affinity (Bernardino and Ganglianone, 2008) [2] . Females construct linear nests with the help of powerful mandibles, creating a series of brood cells ranging from 14 to 20 mm in length. Each brood chamber is separated by partitions approximately 2 mm thick (Vicidomini, 1996) [14] . They collect pollen and nectar to form a pollen mass, which is provisioned inside the brood cell, where an egg is then laid (Prashantha and Belavadi, 2017) [10] . After oviposition, the brood cell is closed with sawdust. The brooding pattern includes two to four generations per annum, and the same nest is reused in the next season. Females remain at the nest entrance until brood emergence (Zafar and Raju, 2014) [15] . Carpenter bee nests are attacked by several types of natural enemies, including parasitoid wasps and flies, predatory wasps, blister beetles, ants, termites, and insectivorous birds (Tamar, 2010) [13] . Phoretic mites are housed in grooves or cavities, which are known as acarinariums. For instance, a number of bees and wasps have acarinaria on their mesosoma and metasoma (Okabe and Makino, 2002) [9] . In large carpenter bees of the Xylocopa species, one metasomal acarinarium on the first tergite of variable sizes and forms, and two comparatively small cavities on the mesosoma. Mutualisms may exist between carpenter bees with acarinaria and their associated mites, but most interactions are considered cleptoparasitism, with mites feeding on the host pollen loaf and faeces (Okabe et al., 2008) [8] .

Materials and Methods

Sample location: Nest samples were collected from college premises of Agricultural College and Research Institute, Madurai, Tamil Nadu Agricultural University, Nest of Xylocopa (K.) pubescens S. was located at Agricultural Research Station, Vellore (TNAU), and KVK Namakkal premises.

Nest Identification: The natural nests constructed by large carpenter bee, Xylocopa spp were located by the frequent visits made by the female bee round the nest entrance with a typical buzzing sound and presence of chewed up saw dust and pollen droppings at the nest entrance. The nests were found on the dried branches of trees like neem, Azadirachta indica L. and Jamun, Syzygium cumini L. with numerous entrance holes.

Nest Data Collection

The nests were brought to the laboratory and recorded the inner contents. Nest entrance was closed with the help of cello tape to allow the adult bees inside for further study. Knife was used to open the nest and recorded the inner content viz., size and shape of the nest entrance, length and width of the nest, number of brood cells per nest, thickness of partitions, number of adult bees per nest and direction of nest entrance. If any immature's present inside the nest was also recorded. The parasites associated with the large carpenter bees were collected and documented. The collected specimens were preserved in 70% ethanol and were later examined using a dissecting microscope. A few nests were collected from Syzyium cumini, Azadirachta indica and natural bamboo. The nest portion between bamboo joints was removed in the field, and 2 days later in the laboratory, the nest was opened by cutting it in half lengthwise. The diameter of each nested shoot was recorded. The investigation was carried out to document the foraging activity of large carpenter bees on flowering crops of cultivated and weed flora.

Results

All the observed nests were linear in shape with the circular nest entrance diameter of 1.25±0.25 cm. The total length and width of the nest were 23.37±9.67 cm and 1.5±0.24cm, respectively. Numerous brood cells were observed but without immature stages. Each brood cell was partitioned using the chewed-up fibrous material. The thickness of the partition was recorded to be 0.48± 0.29 cm with an average range of 0.3 to 1 cm, respectively. The number of adults during nest collection was 2.5±0.5, respectively. The Xylocopa spp nest was linear, simple, unbranched with single nest entrance (Table 1). Nest length was recorded as an average of 23.37±9.61 cm, the brood cells were recorded an average numbers as 5 numbers, whereas similar observations were recorded by Hongjamrassilp and Warrit, (2014) [7] in X. (Biluna) nasalis was 25.40±6.95 cm, brood cells was ranged 0-8 (Table 1). Xylocopa (Biluna) nasalis, X. fenestrate, X. (K.) pubescens, X. (P.) latipes, Xylocopa sp., prefer to forage on plants to collect pollen as well as nectar from both cultivated and uncultivated crops. Most preferred colour in descending order yellow> purple> white> pink (Table 2). In present investigation parasites associated with the solitary bees were collected and documented. As many as 45 first instars of Cissites sp. belonging to Meloidae family, Order: Coleoptera. Instars were golden brown in colour and clinging to the hairs of the both male and female large carpenter bee, X. (Platynopoda) latipes during roosting on the weed (Fig. 4) Phoretic mites belonging to the family Macrocheles sp. belonging to family Macrochelidae order Acarina were collected from female large carpenter bee X.(Koptortosoma) pubescence. Mites were whitish brown in colour and placed in acarinarium, which is placed at the thorasic region (Fig. 5)

Discussion

The nest of Xylocopa (K.) pubescens S. direction of nest entrance was horizontal towards the ground position, nest entrance was directed towards west. The present findings fall in line with the findings of Zafar and Raju (2014) [15] they also observed X. latipes and X. pubescence nests in the dead wood branches of S. cumini, C. siamea and Bamboo culms. Whereas, Batra (1984) [1] , observed the similar nesting behaviour of X. latipes and X. pubescence in dead woods. However, Xylocopa sp., utilized the availability of plant sources in the surrounding habitats, X. sulcatipes preferred C. procera as the nesting site (Hannan et al., 2012) [3] . The Xylocopa sp., nest was linear, simple, unbranched with single nest entrance. The present findings were accordance with the findings of Prashantha and Belvadi (2017) [10] , who reported the nesting behaviour of X. nasalis preferred the pithy stems nest architecture was simple and unbranched. However, few other species of Xylocopa, was reported to construct their nest both branching and unbranching type in dead woods (Rahman and Deka, 2011) [11] . In present investigation, Xylocopa sp. nests not observed in other materials other than woody substrates. But, He and Zhu, (2018) [6] they reported X. xinjiangensis constructed their nests in soil walls of mounds, gullies. Adult females of Xylocopa sp. was observed to excavate the inner content of the dried branches using strong mandibles, brood cell partition was made with the chewed straw. Hongjamrassilp and Warrit (2014) [7] reported similar findings in the nest architecture of X. (Biluna) nasalis in the Bamboo culms, constructed their nest linearly. Additionally, they recorded the nesting biology of the X. nasalis. Moreover, the results are in accordance with the publications of Prashantha and Belavadi (2017) [10] who recorded that X. nasalis mass brood cells were separated with the partitions, which were made by the excavated pithy straw. Nest length was recorded as an average of 23.37±9.61 cm, the brood cells were recorded an average numbers as 5 numbers, whereas similar observations were recorded by Hongjamrassilp and Warrit, (2014) [7] in X. (Biluna) nasalis was 25.40±6.95 cm, brood cells was ranged 0-8. Xylocopa sp. was abundant in Fabaceae and Pedaliaceae, Verbenaceae and Asteraceae, and the least preference was shown towards Bignoniaceae. Present investigation showed that large carpenter bee attracted more to yellow colour. Raju and Rao (2006) reported that large carpenter bees, X. latipes and X. pubescens mostly preferred yellow coloured flowers compared to bluish-white flowers for foraging. In present investigation, Cissites sp. was observed in X. latipes both male and female, Mite population was collected from the acarinarium of the X. (K.) pubescens According to Gerling et al. (1989) [4] phoretic mites were associated with Xylocopa sp. and transport to the nesting location of the large carpenter bee. Deutonumphs of three genera had without stigma act as phoretic viz., Sennertia, Horstia and Torotnia but other stages of the mites were feed on the brood feed of the Xylocopa sp. Dinogamasus mites were associated with large carpenter bee, Xylocopa (K.) sp. present in the abdominal pouches. Calotropis gigantea L.

Cajanus cajan

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