The tropics and subtropics are home to thousands of different types of bees. One bee group that frequently calls an observer’s attention are the stingless bees or Meliponini. In the Neotropics, for example, about half of all bees that one is likely to see on flowers belongs to this group (Chap. 9). Stingless bees can be smaller than a fruit fly or as large as the giant honey bee Apis dorsata. Like honey bees (Apini), stingless bees live in colonies and produce honey. They are potential pollinators of thousands of plant species and play important roles in human cultures. Like many other animals, stingless bees face new challenges in an increasingly human-modified world, including large-scale habitat loss, the widespread use of agrochemicals, climate change and introduced species, all of which put pressure on stingless bee populations (see Sect. 1.9).

Stingless Bees: An Overview

Antennae are the primary sensory organs in insects, where a variety of sensilla are distributed for the perception of the chemical environment. In eusocial insects, colony function is maintained by a division of labor between reproductive and non-reproductive castes, and chemosensation is essential for regulating their specialized social activities. Several social species in Hymenoptera display caste-specific characteristics in antennal morphology and diversity of sensilla, reflecting their differential tasks. In termites, however, little is known about how the division of labor is associated with chemosensory morphology among castes. Using light and scanning electron microscopy, we performed antennal morphometry and characterized the organization of sensilla in reproductive (female and male alates) and non-reproductive (worker and soldier) castes in the Formosan subterranean termite, Coptotermes formosanus Shiraki. Here, we show that the antennal sensilla in alates are twice as abundant as in workers and soldiers, along with the greater number of antennal segments and antennal length in alates. However, all castes exhibit the same types of antennal sensilla, including basiconicum, campaniformium, capitulum, chaeticum I, chaeticum II, chaeticum III, marginal, trichodeum I, and trichodeum I. The quantitative composition of sensilla diverges between reproductive and non-reproductive castes, but not between female and male alates or between worker and soldier castes. The sensilla display spatial-specific distribution, with basiconicum exclusively and capitulum predominantly found on the ventral side of antennae. In addition, the abundance of chemosensilla increases toward the distal end of antennae in each caste. This research provides morphological signatures of chemosensation and their implications for the division of labor, and suggests future neurophysiological and molecular studies to address the mechanisms of chemical communication in termites.

https://www.mdpi.com/2075-4450/12/7/576/pdf

Comparative Antennal Morphometry and Sensilla Organization in the Reproductive and Non-Reproductive Castes of the Formosan Subterranean Termite.

Stingless bee nests contain valuable resources, such as honey, pollen, cerumen, batumen, resin, larval food and finally, the cavity and the bees themselves (Chap. 3). It is, therefore, unsurprising that other animals attempt to gain access to these resources. This, in turn, can lead to substantial predation-related mortality of stingless bee colonies. In Uganda, for instance, 12% of colonies from five species died from predation per year (Kajobe and Roubik 2006) and in a Costa Rican habitat, ~40% of all mortality was caused by predation (Slaa 2006). In an Indonesian population of Tetragonula minangkabau, 47% of all colonies died from either predation or parasitism (Inoue et al. 1993). Eltz et al. (2002), on the other hand, found that predation was rarely a cause for colony death in a Malaysian habitat.

Enemies, Dangers and Colony Defence

The focus of bee neuroscience has for a long time been on only a handful of social honeybee and bumblebee species, out of thousands of bees species that have been described. On the other hand, information about the chemical ecology of bees is much more abundant. Here we attempted to compile the scarce information about olfactory systems of bees across species. We also review the major categories of intra- and inter-specific olfactory behaviors of bees, with specific focus on recent literature. We finish by discussing the most promising avenues for bee olfactory research in the near future. 

The neuroecology of olfaction in bees.

Abstract Social wasps have a widespread Neotropical distribution and are important pollinators and biological control agents for pest insects. The foraging activity of wasps is influenced by biotic and abiotic factors that are detected by the antennal sensilla that vary according to species, sex, caste, and environmental conditions. This study compares the types and quantities of antennal sensilla with a scanning electron microscope between the nocturnal Apoica flavissima and the diurnal Polistes simillimus wasps. Six types of sensilla were found in the antennae of both species: placoid, coeloconic, basiconic-type 1, basiconic-type 2, trichoid-type 1, and trichoid-type 2. Sensilla chaetica were found only in the scape and pedicel of A. flavissima. In the nocturnal wasp, there are 19,132.27 ± 1,247.72 sensilla in the left and 17,746.46 ± 1,477.46 in the right antennae, whereas in the diurnal wasp 14,936.72 ± 1,271.69 in the left and 16,090.82 ± 1,345.3 in the right antennae. A. flavissima has a longer antennal length and number of sensilla than P. simillimus. The higher number of antennal sensilla in the nocturnal wasp is not linked with the antennal size. The association of antennal sensilla functions with ecological and behavioral factors of A. flavissima and P. simillimus are discussed.

S. Veiga Ravaiano

Papers

Morphological assessment of the sensilla of the antennal flagellum in different castes of the stingless bee Tetragonisca fiebrigi