Cristiano Menezes

A morphologically specialized soldier caste improves colony defense in a neotropical eusocial bee

Division of labor among workers is common in insect societies and is thought to be important in their ecological success. In most species, division of labor is based on age (temporal castes), but workers in some ants and termites show morphological specialization for particular tasks (physical castes). Large-headed soldier ants and termites are well-known examples of this specialization. However, until now there has been no equivalent example of physical worker subcastes in social bees or wasps. Here we provide evidence for a physical soldier subcaste in a bee. In the neotropical stingless bee Tetragonisca angustula, nest defense is performed by two groups of guards, one hovering near the nest entrance and the other standing on the wax entrance tube. We show that both types of guards are 30% heavier than foragers and of different shape; foragers have relatively larger heads, whereas guards have larger legs. Low variation within each subcaste results in negligible size overlap between guards and foragers, further indicating that they are distinct physical castes. In addition, workers that remove garbage from the nest are of intermediate size, suggesting that they might represent another unrecognized caste. Guards or soldiers are reared in low but sufficient numbers (1–2% of emerging workers), considering that <1% usually perform this task. When challenged by the obligate robber bee Lestrimelitta limao, an important natural enemy, larger workers were able to fight for longer before being defeated by the much larger robber. This discovery opens up opportunities for the comparative study of physical castes in social insects, including the question of why soldiers appear to be so much rarer in bees than in ants or termites.

Bees for development: Brazilian survey reveals how to optimize stingless beekeeping.

Stingless bees are an important asset to assure plant biodiversity in many natural ecosystems, and fulfill the growing agricultural demand for pollination. However, across developing countries stingless beekeeping remains an essentially informal activity, technical knowledge is scarce, and management practices lack standardization. Here we profited from the large diversity of stingless beekeepers found in Brazil to assess the impact of particular management practices on productivity and economic revenues from the commercialization of stingless bee products. Our study represents the first large-scale effort aiming at optimizing stingless beekeeping for honey/colony production based on quantitative data. Survey data from 251 beekeepers scattered across 20 Brazilian States revealed the influence of specific management practices and other confounding factors over productivity and income indicators. Specifically, our results highlight the importance of teaching beekeepers how to inspect and feed their colonies, how to multiply them and keep track of genetic lineages, how to harvest and preserve the honey, how to use vinegar traps to control infestation by parasitic flies, and how to add value by labeling honey containers. Furthermore, beekeeping experience and the network of known beekeepers were found to be key factors influencing productivity and income. Our work provides clear guidelines to optimize stingless beekeeping and help transform the activity into a powerful tool for sustainable development.

Pollination by Sexual Mimicry in Mormolyca ringens: A Floral Chemistry that Remarkably Matches the Pheromones of Virgin Queens of Scaptotrigona sp.

The chemical composition of some volatile (2-heptanol) and nonvolatile constituents (a homologous 9-alkene/alkane series) of Mormolyca ringens flowers and Scaptotrigona sp. queen waxes (homologous 9-alkene/alkane series) and cephalic extracts (homologous series of 2-alkanols, including 2-heptanol) involved with the pseudocopulation or sexual mimicry in Orchidaceae pollination is compared. The similarity in chemical composition of flowers and insects is assigned to the chemically induced copulatory activity in Scaptotrigona males.

The role of wax and resin in the nestmate recognition system of a stingless bee, Tetragonisca angustula

Recent research has shown that entrance guards of the stingless bee Tetragonisca angustula make less errors in distinguishing nestmates from non-nestmates than all other bee species studied to date, but how they achieve this is unknown. We performed four experiments to investigate nestmate recognition by entrance guards in T. angustula. We first investigated the effect of colony odours on acceptance. Nestmates that acquired odour from non-nestmate workers were 63% more likely to be rejected while the acceptance rate of non-nestmates treated with nestmate odour increased by only 7%. We further hypothesised that guards standing on the wax entrance tube might use the tube as an odour referent. However, our findings showed that there was no difference in the acceptance of non-nestmates by guards standing on their own colony’s entrance tube versus the non-nestmate’s entrance tube. Moreover, treatment of bees with nestmate and non-nestmate resin or wax had a negative effect on acceptance rates of up to 65%, regardless of the origin of the wax or resin. The role of resin as a source of recognition cues was further investigated by unidirectionally transferring resin stores between colonies. Acceptance rates of nestmates declined by 37% for hives that donated resin, contrasting with resin donor hives where acceptance of non-nestmates increased by 21%. Overall, our results confirm the accuracy of nestmate recognition in T. angustula and reject the hypothesis that this high level of accuracy is due to the use of the wax entrance tubes as a referent for colony odour. Our findings also suggest that odours directly acquired from resin serve no primary function as nestmate recognition cues. The lack of consistency among colonies plus the complex results of the third and fourth experiments highlight the need for further research on the role of nest materials and cuticular profiles in understanding nestmate recognition in T. angustula.

The Role of Useful Microorganisms to Stingless Bees and Stingless Beekeeping

Bacteria, molds, and yeasts associated with bees have been studied for a long period. Although they seem to play an important role for bee nutrition and protection against harmful microorganisms, few studies have focused on their function and this subject is still very controversial. Although stingless bees (Apidae: Meliponini) share many similarities with Apis mellifera, this diverse group still conceals many particularities that have not been explored at all. In this chapter, we discuss the role of non-pathogenic microorganisms from stingless bee colonies and we focus on their applicability to stingless bee keeping. Our aim is to stimulate studies on functional aspects of microorganisms from stingless bees and their products where upon microorganisms are involved.

First discovery of a rare polygyne colony in the stingless bee Melipona quadrifasciata (Apidae, Meliponini)

1 Laboratorio de Abelhas, Departamento de Ecologia, IB, Universidade de Sao Paulo, Rua do Matao Trav. 14, 321, 05508-090 Sao Paulo, Sao Paulo, Brasil 2 Laboratorio de Abelhas, Departamento de Biologia, FFCLRP, Universidade de Sao Paulo, Av. Bandeirantes, 3900, 14040-901, Ribeirao Preto, Sao Paulo, Brasil 3 Laboratory of Entomology, Zoological Institute, Catholic University of Leuven, Naamsestraat 59, 3000 Leuven, Belgium

Repeated evolution of soldier sub-castes suggests parasitism drives social complexity in stingless bees

The differentiation of workers into morphological castes represents an important evolutionary innovation that is thought to improve division of labor in insect societies. Given the potential benefits of task-related worker differentiation, it is puzzling that physical worker castes, such as soldiers, are extremely rare in social bees and absent in wasps. Following the recent discovery of soldiers in a stingless bee, we studied the occurrence of worker differentiation in 28 stingless bee species from Brazil and found that several species have specialized soldiers for colony defence. Our results reveal that worker differentiation evolved repeatedly during the last ~ 25 million years and coincided with the emergence of parasitic robber bees, a major threat to many stingless bee species. Furthermore, our data suggest that these robbers are a driving force behind the evolution of worker differentiation as targets of robber bees are four times more likely to have nest guards of increased size than non-targets. These findings reveal unexpected diversity in the social organization of stingless bees.Although common in ants and termites, worker differentiation into physical castes is rare in social bees and unknown in wasps. Here, Grüter and colleagues find a guard caste in ten species of stingless bees and show that the evolution of the guard caste is associated with parasitization by robber bees.

Soldiers in a Stingless Bee

The differentiation of workers into morphological subcastes (e.g., soldiers) represents an important evolutionary transition and is thought to improve division of labor in social insects. Soldiers occur in many ant and termite species, where they make up a small proportion of the workforce. A common assumption of worker caste evolution is that soldiers are behavioral specialists. Here, we report the first test of the “rare specialist” hypothesis in a eusocial bee. Colonies of the stingless bee Tetragonisca angustula are defended by a small group of morphologically differentiated soldiers. Contrary to the rare specialist hypothesis, we found that soldiers worked more (+34%–41%) and performed a greater variety of tasks (+23%–34%) than other workers, particularly early in life. Our results suggest a “rare elite” function of soldiers in T. angustula, that is, that they perform a disproportionately large amount of the work. Division of labor was based on a combination of temporal and physical castes, but soldiers transitioned faster from one task to the next. We discuss why the rare specialist assumption might not hold in species with a moderate degree of worker differentiation.

The bigger, the smaller: relationship between body size and food stores in the stingless bee Melipona flavolineata

Worker body size is a key feature for stingless bee biology, being related with the foraging range of colonies. We correlated the intertegular span, corbicular area, head width, and interocular distance, as well as the fresh weight, from workers of Melipona flavolineata, a species from the Amazonian Region, with the stored reserves of honey and pollen. The food reserves decreased with the increase of rainfall, and there was a significant correlation between intertegular span, corbicular area, and food stores. The corbiculae was inversely correlated with food reserves, while the width of thorax was positively related. We consider the allometric variation of thorax width and corbicular area as a mechanism to adjust colonial food collection, since larger corbiculae would maximize the pollen-gathering during the rainy, dearth periods, and when the resource supply increases, the workers increase in the width of thorax, being able to explore larger areas and replenish the colonial food stores.

Seasonal availability of floral resources and ambient temperature shape stingless bee foraging behavior (Scaptotrigona aff. depilis)

The foraging success of a bee species is related to a combination of climatic factors and resource availability. Here, we analyzed how food storage by the stingless bee Scaptotrigona aff. depilis relates to the seasonal variation in floral resources availability in a tropical environment with two well-defined seasons. We found a positive relationship between the amount of food stored and resource availability, suggesting that colonies intensify food collection in the season with higher food availability (rainy season). This ensures the perennial state of stingless bee colonies during the dry season (food scarcity and lower ambient temperatures). Bees collected pollen from at least 60 plant species, but food pots were dominated by just nine plants. Additionally, S. aff depilis attempted to unevenly use the plant species for food storage in the rainy season, which indicates that the colonies maximize their food intake as soon as resources are available.