**2.2 Caste and colony function**

*Modern Beekeeping - Bases for Sustainable Production*

key characteristics [4, 13].

pollen baskets [4].

and reproductive organs [4, 14].

three main segments: the head, thorax, and abdomen.

mono-tone (clear white entire of wing), as shown in **Figure 5A**.

color, pattern of wing venation, and size and shape of the corbiculate [4]. However, all stingless bee species have the same basic morphological body patterns as other Hymenopterans (**Figure 4**). Thus, the body of stingless bees can be separated into

On the head or prosoma of a single bee, the main organs are eyes (compound eyes and dorsal ocelli), antennae, and mouth parts. All structures on the prosoma are used to interact with their environment. For stingless bee identification, the size, shape, and number of teeth on the mandibles have been used as the primary

On the thorax or mesosoma, two pairs of wings and three pairs of legs are attached and are involved in the locomotion of the bee. These appendages are moved by groups of thorax muscles [14]. Two types of forewing can be observed in Indo-Malayan stingless bee, two-tone (darker at base and clear white at apex) and

In worker bees, hind legs which are modified for pollen collection are called pollen baskets or corbicula (**Figure 5B**). The tibia is broadly expanded and slightly concave with curved hairs along the edge for keeping the pollen load. Moreover, the inner surface of the hind basitarsus segment is covered with short bristles that are used for grooming the pollen from the body and transferring the pollen to the

The abdomen or metasoma of adult stingless bees consists of nine segments, but only second–seventh segments are externally visible [14]. Unlike honey bees, wax glands located on the tergites (dorsal plates) of the abdomen are active and produce wax in younger adult workers. Most internal organs and systems are found in this body part, including digestive organs, ventral nervous system, circulatory system,

*External morphology of* Homotrigona fimbriata *(Smith, 1857) worker: (1) antennae, (2) proboscis, (3) mandible, (4) malar space, (5) compound eye, (6) ocelli, (7) pronotum, (8) tegula, (9) scutellum, (10) propodium, (11) forewing, (12) hind wing, (13) hind tibia, (14) pollen basket or corbicula, (15) hind* 

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**Figure 4.**

*basitarsus, and (16) hamuli on hind wing.*

In social hymenopteran colonies, there is a division of labor between females of the colony [15]. Two castes (queen and worker) are found in a colony of stingless bees. Like other corbiculate bees, stingless bee colonies consist of two sexes (female and male), which are different in size and shape of external morphology (**Figure 6**). A haplodiploid sex determination system has been described to explain how female and male are produced in all stingless bees [4]. Both the female queen and the worker, called diploid females, develop from fertilized eggs laid by the mother queen, so they have two sets of chromosomes. In contrast, stingless bee males are produced from unfertilized eggs which is known as arrhenotokous parthenogenesis [16], meaning they carry only the mother's genetic materials [4].

A stingless bee colony consists of a single female queen (fertile female), several hundred to several thousand unfertile female workers, and a few hundred males [17]. Similar to the honey bee of the genus *Apis*, stingless bee workers perform most activities both inside and outside the nest, including cell construction, taking care of the queen and larvae, defending the nest, as well as foraging for food and other

#### **Figure 5.**

*(A) Fore and hind wings of two Indo-Malayan stingless bee species,* Tetragonilla collina *and* Lophotrigona canifrons*, show the color tone of forewing. (B) Outer and inner views of hind leg of* Tetrigona apicalis *worker showing pollen basket on the tibia.*

**Figure 6.** *Sexual dimorphism in* Tetrigona apicalis*.*

colony needed materials [17, 18]. Interestingly, the progression of different duties of worker bees corresponds to age after adulthood, known as age polyethism [19]. This phenomenon is also seen in honey bees [19, 20].

Generally, five major stingless bee worker activities are recognized, namely, (1) cleaning blood chambers and feeding larvae, (2) constructing the nest, (3) receiving and processing nectar, (4) guarding in front of the nest entrance, and (5) foraging for food sources and other materials [21, 22]. Similar to *Apis*, young stingless bee workers work inside the nest. They have active wax glands on the tergites, and their main roles are constructing brood cells and cleaning the brood area. After 2 weeks, the ovaries of workers become active, and they produce trophic eggs [4] for feeding the mother queen. They also receive the nectar from foragers and dehydrate it to become honey. Older workers (3–4 weeks old) perform activities related to guarding. At this age, the workers perform short-distance flights for nest orientation [4]. In the final stage (about 1 month old), the worker becomes a forager. However, age polyethism in stingless bees is flexible, meaning that workers can continue or revert across different activities, depending on colony needs [4, 23].
