Tetragonula laeviceps (Hymenoptera: Apidae: Meliponini): Morphology, Morphometric, and Nest Structure

Article history: Received: 17 Apr 2020 Accepted: 02 Des 2020 Published: 31 Des 2020 Background: Stingless bees is one group of eusocial insects living together in the hive. There are around 46 species of stingless bee in Indonesia with different morphological, morphometric and hive structure characteristics. This study aimed to describe the morphological, morphometric and beehives structure of Tetragonula laeviceps from Yogyakarta. Methods: Survey method is used by taking three sampling points of bamboo, house building and livestock crates in Bantul Regency. Sampling points determined by Purposive sampling method. An XSZ-107 BN binocular microscope analyzed samples of T. laeviceps with Optilab viewer and Image Raster software. Results: The results showed morphological characters of T. laeviceps are dominated shiny-black body, brownish-yellow antennas, klipeus on a head covered by fine silver hair, brownish-yellow mandible with two teeth, mesonotum in thorax covered by brownish to black hair, scutellum extended to propodeum, the ribbon of hair on the dorsal thorax is not very clear, and the hind tibia is rather hairy. Morphometric of T. laeviceps included body length between 3.44 3.76 mm, head width 1.55 1.70 mm, front wing length with tegula 3.76 4.37 mm, length of rear limbs tibia 1.371.57 mm, and the number of hamuli as many as 5. The beehive structure consisted of oval-shaped entrance formed funnel and varying internal hive in terms of the number of saplings, pollen cells, and honey cells. Conclusions: T. laeviceps have morphological, morphometric and hive structure characteristics that are different from other species and variated compared to similar species from other regions.


Introduction
Stingless bees are a eusocial insect that lives together in a colony and has many important life roles. These bees are classified in Apidae, subfamily Apinae, and tribe Meliponini (Borror, D. Triplehorn, C., & Johnson 1992;Michener 1944;Trianto, M., Kaini, Saliyem, Warsih, E. 2020). Stingless bees include bees with a large number of genera, which is about 55 genera divided into 61 sub-genera with different morphological, morphometric, and nest structure characters for each species (Rasmussen 2008;Trianto, M., Kaini, Saliyem, Warsih, E. 2020). One species of stingless bees is Tetragonula laeviceps, spread across in island, one of them in Java to be precise in Bantul Regency, Special Region of Yogyakarta Province.
Tetragonula laeviceps is one species of stingless bees. The morphological characteristics of T. laeviceps is the body predominantly shiny black, mesoscutum black and fully covered with yellowish setae in posterior. The number of hamuli 5 per hindwing (Cockerell 1911;Smith 2012;Trianto, M., & Purwanto 2020). In nature, this bee has a morphometric size that varies from region to region. These bees can also be found in almost all habitats or locations ranging from dead tree trunks, bamboo, and house buildings with a distance of about 1-5 m from the ground. The nest structure consists of the nest entrance in a tube surrounded by a blackish resin. The hive is mouth can be in the form of internal and external tubes as a way for bees to enter and exit the hive internall (Chinh et al., 2005).
In the identification process of stingless bees, based on morphological characteristics, morphometric, and nest structure need to be known because they can help determine the type of stingless bees themselves. This information can be also used as initial information before carrying out the cultivation or conservation process of stingless bees.
Research on the morphological characteristics, morphometric, and nest structure of T. laeviceps it's very lacking. Currently, research on these species is still limited to diversity (Suriawanto, Atmowidi, and Kahono 2017;Trianto, M., Kaini, Saliyem, Warsih, E. 2020), description of the entrance to the nest and source of food (Rizka, 2016). This study described morphological characteristics, morphometric, and nest structure of T. laeviceps from Bantul Regency, Special Region of Yogyakarta Province.
Determination of sampling sites using a roaming method. Total of 3 colonies of T. laeviceps was used as a sample. The specimens collected (15 individuals of each colony) were put into a bottle with 96% ethanol. Next, perform the pining process by an insect needle into the mesoscutum. Samples are dried in the oven at 35 degree Celsius for 24 hrs.
Observations of the entrance and internal structure of the nest were carried out at three stingless bee colonies. The entrance to the nest was observed for the shape, colour and surface texture. The internal structures of the hives that were observed were tiller cells, pollen cells, and honey cells (Suriawanto et al., 2017) (Figure 2).

Data analysis
Data analysis was performed by calculating the minimum and maximum length (mm) of the measurement of the morphometric characters of the stingless bee, namely body length (BL), head width (HW), length of forewing including tegula (WL1), the distance between M-Cu bifurcation (WL2), and hind tibia length (HTL). Calculate the percentage area of the stingless bee nest composition, namely nest area / total nest area x 100%.

Morphological characteristics of T. laeviceps
The body of T. laeviceps predominantly shiny black. Compound eyes reddish, ocelli blackish and large. Clypeus blackhead and fully covered with fine white hairs. Antennal has 11 flagellomeres, scape yellowish-brown, and pedicel brown. Mandible has two teeth and the colour brown and slightly black in basal. Mesoscutum black and fully covered with yellowish setae in posterior. Tegula is brown. Hind tibiae short, corbicula pear shape, sparsely covered with long setae in apical but short in basal, entirely black and basitarsi is wholly black. First to five gastral tergites are fully dark brown in dorsal-the number of hamuli 5 per hindwing ( Figure 3).

Nest structure of T. laeviceps
Three colonies of T. laeviceps were observed in bamboo cavities ( Figure 5), building cavities ( Figure 6) and beekeeping (Figure 7). Overall, the entrance to the nests in colonies 1, 2 and 3 is in the form of oval holes, with shortlong tubes, yellow to brownish-black, and the texture of the entrance to the nest is soft or not hard (Figure 5-7).
In the colony, honey cells can be distinguished from pollen cells and brood cells. Honey cells are blackishbrown, and pollen cells are brown. Brood cells are smaller than honey cells and light brown. Also, in the nest, there aral visible rocks surrounding (Figure 8). The composition nest of T. laeviceps is brood cells (51.44%), honey cells (20.49%), pollen cells (16.28%), and batumen (11.79%) (

Morphological and morphometric characteristics of T. laeviceps
The morphological characters of the T. laeviceps from this study are the body predominantly shiny black. Compound eyes reddish, ocelli blackish and large. Clypeus blackhead and fully covered with fine white hairs. Antennal has 11 flagellomeres, scape yellowish-brown, and pedicel brown. Mandible has two teeth and the colour brown and slightly black in basal. Mesoscutum black and fully covered with yellowish setae in posterior. Tegula is brown. Hind tibiae short, corbicula pear shape, sparsely covered with long setae in apical but short in basal, entirely black and basitarsi is wholly black. First to five gastral tergites are fully dark brown in dorsal. The number of hamuli 5 per hindwing. The morphological characters following the description of Efin, A., Atmowidi, T., & Prawasti (2019), Karimah (2017). Manarudin (2019), Sakagami, S. F., Inoue, T., , Sakagami (1978), Smith (2012), .
Furthermore, T. laeviceps specimen in this study have a body size (3.44-3.76 mm), shorter than the specimen described by Sakagami (1978) that was using a specimen from Sri Lanka and Asia (4.00-4.60 mm) and specimen from Banten (4.31-4.58 mm) (Efin et al. 2019). Meanwhile, when compared with the specimen by Michener, (1944) and Smith, (2012), who used specimen from Singapore (3.50 mm) and who used specimen from Sulawesi (3.40-3.43 mm) (Suriawanto et al. 2017), who used samples from Special Region of Yogyakarta (3.64-3.68 mm), the specimen in this study had a longer body size .
The workers' bees of T. laeviceps of this study have different sizes, but not too significant. In contrast, the specimen's morphometry has variation in size compared to the same species reported from other areas. The differences in the size of the worker bees are a morphological adaptation to different environmental conditions. Gaston, (2008) and Novita et al. (2013) concluded that changes in temperature or environmental conditions would cause living things to adapt morphologically to adjust to the environment flight and foraging activities. Also, this variation is supported by Roubik, (2006) and Ruttner, (1987) that the body size of worker bees is generally considered form of adaptation in foraging activities and exploiting flower resources. Furthermore, the result of this study similar to research by Novita et al. (2013) and Raffiudin et al. (1999) using the honey bee samples (Apis cerana).

Nest structure of T. laeviceps
The nest structure of the T. laeviceps from this study consists of the nest entrance, honey cells, brood cells, pollen cells, and batumen. The nest structure described in this study, similar to the description of Karimah, (2017). Batumen is made from a mixture of wax and resin called cerumen (Michener, 1944). Batumen is a layer of cerumen that covers the entire surface of the nest. However, some stingless bees use mud as a mixture to form stone (Michener, 1944;Salmah et al., 1990).
Furthermore, Kelly et al. (2014) reported that the entrance to the T. laeviceps in Kelantan, Malaysia namely funnel-shaped, black, and rigid with a smooth and rough surface. Meanwhile, the entrance to the hives of stingless bees colonies 1 to 3 in this study is similar to data by Chinh et al. (2005). Also , Sakagami, (1978) reported that there were variations at the entrance to T. laeviceps nests, namely entrances with extended channels, nests without channels at the entrance but with rain protection (raintight) around them, and nests without channels and protection. According to Sakagami, (1978), there are variations in the stingless bees' entrance due to the hive's environmental conditions. Continuous nest entrances will be built in line with the growth of the stingless bee colony. The construction of the entrance to the nest decreases as the population in the colony decreases. Over time, a decrease in population causes a decrease in foraging activity and a narrowing of the nest entrance. Roubik, (2006) adds that the inlet's extension in the hive is caused by the age of the hive, genetic factors of bees and environmental conditions such as predators, parasites, symbionts, rain, wind and sun.

Declaration statement
The authors reported no potential conflict of interest.