Robin Michael Crewe

University of Pretoria | UP · Department of Zoology and Entomology

SIGNIFICANCE: • The laying workers of the Cape honey bee continue to negatively affect the South African beekeeping industry, with more losses suffered in the northern regions of the country • The reproductive parasites enter susceptible host colonies, activate their ovaries, and lay diploid eggs, leading to colony dwindling and collapse. • Diploid...

Cohesion in social insect colonies is maintained by use of chemical signals produced by the queen, workers, and brood. In honey bees in particular, signals from the queen and brood are crucial for the regulation of reproductive division of labor, ensuring that the only reproductive female individual in the colony is the queen, whereas the workers r...

Social insect societies are characterized by a high level of organization exemplified by strict division of reproductive labor and worker division of labor based on age polyethism. This order is mediated through the use of a remarkably complex array of pheromonal signals produced by all members of the colony and regulated by social contexts. In thi...

Visual and olfactory communication are vital for coordinated group hunting in most animals. To hunt for prey, the group raiding termite specialist ant Megaponera analis, which lacks good vision must first confirm the presence or absence of conspecific raiders. Here we show that, M. analis uses olfactory cues for intra-specific communication and sho...

Following a Workshop on the Ethics of Scholarly Publishing on 11 April 2018, and with the collective goal of advancing research integrity in South Africa, the Academy of Science of South Africa (ASSAf), the Council for Higher Education (CHE), the National Research Foundation (NRF), the Department of Higher Education and Training (DHET) and Universi...

Colony losses due to social parasitism in the form of reproductive workers of the Apis mellifera capensis clones results from the production of queen-like pheromonal signals coupled with ovarian activation in these socially parasitic honey bees. While the behavioral attributes of these social parasites have been described, their genetic attributes...

Recent studies have emphasized the role of the western honey bee, Apis mellifera, as a managed agricultural species worldwide, but also as a potential threat to endangered wild pollinators. This has resulted in the suggestion that honey bees should be regulated in natural areas to conserve wild pollinators. We argue that this perspective fails to a...

The primer and releaser effects of dominant honey bee workers’ tergal gland pheromones are not known under queenless conditions. The Cape honey bee, Apis mellifera capensis, is the ideal model to investigate such question since workers normally reproductively dominate workers of all other subspecies. We determined the effects that short- and long-t...

Social cohesion in social insect colonies can be achieved through the use of chemical signals whose production is caste-specific and regulated by social contexts. In honey bees, queen mandibular gland pheromones (QMP) maintain reproductive dominance by inhibiting ovary activation and production of queen-like mandibular gland signals in workers. We...

One of the responses that honey bee workers can make in the event of queen loss is to develop into false queens. False queens are workers that exhibit both behavioural and physiological traits similar to those of a true queen. However, the presence of more than one false queen in a colony distorts the established hierarchies. As transformation into...

The honeybee queen’s mandibular gland pheromones (QMP) are essential for the suppression of worker reproduction. Worker ovary activation is regulated by alternative splicing of a CP2-transcription factor named gemini. Since workers with activated ovaries also produce QMP in their mandibular glands, we tested whether alternative splicing of gemini a...

Pheromonal control by the honey bee queen is achieved through the use of secretions from diverse glandular sources, but the use of pheromones from a variety of glandular sources by reproductively dominant workers, has not previously been explored. Using the social parasite, Apis mellifera capensis clonal worker, we studied the diversity of glandula...

1. Increasing global human populations and climate change not only increase the demand for food but require it to be supplied in sustainable quantities. One crucial aspect for sustainability is to ensure pollinator services for crop production and ecosystem services. 2. The global distribution of universal bee pollinators and the different degrees...

Scholarly academies have been in existence for about 350 years, with the oldest being those that were established in Europe in the 17th century. These institutions consist of groups of individuals who are elected by their peers to be members (often called fellows); since the middle of the 19th century, election to the august ranks of most academies...

The history of scholarly journal publishing is generally dated from the appearance of the Philosophical Transactions of the Royal Society of London in 1665.1 The notable features of this publication are that it is the property of a learned society, and at the time of its inception reflected the deliberations of the scholars of the day from across E...

Varroa destructor is considered the most damaging parasite affecting honeybees (Apis mellifera L.). However, some honeybee populations such as the savannah honeybee (Apis mellifera scutellata) can survive mite infestation without treatment. It is unclear if survival is due to resistance mechanisms decreasing parasite reproduction or to tolerance me...

Some parasites of social insects are able to exploit the exchange of food between nestmates via trophallaxis, because they are chemically disguised as nestmates. However, a few parasites succeed in trophallactic solicitation although they are attacked by workers. The underlying mechanisms are not well understood. The small hive beetle (=SHB), Aethi...

Secretions from tergal glands are part of a queen’s pheromonal control of worker reproduction in honey bees. However, in queenless honey bee colonies, workers compete to gain pheromonal, and hence reproductive dominance, over nestmates with ontogenetic changes in their glandular secretions that affect the behavioral or physiological responses of ot...

Abstract – Secretions from the mandibular glands of honeybees have been studied extensively, with those of queens dominated by ώ-9 fatty acids and ώ-10 fatty acids dominating those of non-laying workers. Apis mellifera adansonii (Latreille) is one of the widely distributed subspecies of African honeybees. However, its mandibular gland pheromones ha...

Murray Sheldon Blum, of Athens, Georgia, beloved husband, father, and grandfather, pioneering scientist and explorer of the natural world, exuberant lover of life, family, friends, good jokes and bad puns, bright colors, operatic arias, and insects of all varieties, died peacefully at home on Sunday, 22 March 2015. He was 85 years old. Born in Phi...

The devastating effects of Varroa destructor Anderson & Trueman on European honeybee colonies (Apis mellifera L.) have been well documented. Not only do these mites cause physical damage to parasitised individuals when they feed on them, they also transmit viruses and other pathogens, weaken colonies and can ultimately cause their death. Neverthele...

The African termite-raiding ant Pachycondyla analis Latreille (Hymenoptera: Formicidae) organizes group raids on termites of the sub-family Macrotermitinae. Termites and ants occupy and share similar habitats, resulting in a co-evolutionary arms race between termites as prey and ants as predators. The present study explored whether P. analis uses s...

This study reports honey bee, Apis mellifera L., colony losses that occurred in South Africa over two consecutive years. The total losses were 29.6% (95% CI: 22.8-37.5) in 2009-2010 and 46.2% (95% CI: 37.3-55.0) in 2010-2011. Furthermore, the study shows that the capensis worker social parasite, a problem unique to southern Africa, is the main perc...

Termite raiding behaviour of the African poneromorph ant Pachycondyla analis was studied at Mpala, Kenya. In all, 330 raids were observed with the raiding activity showing peaks in the morning and evening. Time spent at the termite source was positively correlated with the numbers of termites taken. The sizes of foraging parties, number of termites...

The loss of Apis mellifera L. colonies in recent years has, in many regions of the world, been alarmingly high. No single cause has been identified for these losses, but the interactions between several factors (mostly pathogens and parasites) have been held responsible. Work in the Americas on honeybees originating mainly from South Africa indicat...

Pachycondyla analis Latreille (Hymenoptera: Formicidae) is a common African Ponerine ant that organizes group raids on termites considered a huge burden to agriculture. This ant has been the subject of various entomological and natural history studies aimed at understanding their group raiding behaviour and impact on the ecosystem as well as the ro...

The ant genus Cardiocondyla is characterized by a pronounced male diphenism with wingless fighter males and winged disperser males. Winged males have been lost convergently in at least two species-rich clades. Here, we describe the morphological variability of males of Cardiocondyla venustula from uThukela valley, South Africa. Winged males appear...

The loss of Apis mellifera L. colonies in recent years has, in many regions of the world, been alarmingly high. No single cause has been identified for these losses, but the interactions between several factors (mostly pathogens and parasites) have been held responsible. Work in the Americas on honeybees originating mainly from South Africa indicat...

Laying workers of the Cape honeybee parthenogenetically produce female offspring, whereas queens typically produce males. Beekman et al. confirm this observation, which has repeatedly been reported over the last 100 years including the notion that natural selection should favor asexual reproduction in Apis mellifera capensis. They attempt to suppor...

The state of knowledge on the pheromones of Asian honeybees is discussed. The queen mandibular pheromone is known to elicit short- (retinue formation, swarm stabilisation and drone attraction) and long-term (inhibition of queen rearing) behaviours. The primer pheromones produced by the mandibular and Dufour’s glands and the releaser ones associated...

In eusocial insects the production of daughters is generally restricted to mated queens, and unmated workers are functionally sterile. The evolution of this worker sterility has been plausibly explained by kin selection theory [Hamilton W (1964) J Theor Biol 7:1-52], and many traits have evolved to prevent conflict over reproduction among the femal...

Honey bee colonies are characterised by well-developed reproductive division of labour between the queen and workers. Here, we test whether this reproductive division of labour is evident in both the socially parasitic workers that invade a colony as well as in their offspring generation. We infected six Apis mellifera scutellata host colonies with...

Sustaining apiculture worldwide has been threatened by bee diseases and unexplained colony losses. African honeybee populations seem healthier and no major losses have been reported despite the presence of all the major pests and diseases. The scattered colonies in the large wild population of the continent might ensure slow pathogen spread and thu...

Sustaining apiculture worldwide has been threatened by bee diseases and unexplained colony losses. African honeybee populations seem healthier and no major losses have been reported despite the presence of all the major pests and diseases. The scattered colonies in the large wild population of the continent might ensure slow pathogen spread and thu...

Determining the extent and causes of barriers to gene flow is essential for understanding sympatric speciation, but the practical difficulties of quantifying reproductive isolation remain an obstacle to analysing this process. Social parasites are common in eusocial insects and tend to be close phylogenetic relatives of their hosts (= Emery's rule)...

The nutritional needs of bees are supplied by nectar carbohydrates and by protein and other nutrients in pollen but little is known of how bees achieve nutritional balance. Using newly emerged caged worker honeybees (Apis mellifera scutellata), we investigated whether bees maintain their intake target when confined to pairs of imbalanced complement...

Small hive beetles, Aethina tumida Murray, (Coleoptera: Nitidulidae) are native to subSaharan Africa where they parasitize honey bee (Apis mellifera L) colonies (Lundie 1940). Small hive beetles feed on pollen, brood and honey inside honey bee hives (Lundie 1940). Pupation occurs in the soil and the transitions from larvae to pupae to adult are vul...

In honeybees, worker reproduction is mainly regulated by pheromones produced by the brood and the queen. The source of one of the queen pheromones influencing worker reproduction has been located in the mandibular glands. In nonlaying workers, this gland’s profile is dominated by fatty acids that are incorporated into the food given to the brood an...

The combination of polygyny and natural queenlessness is uncommon in ants. The ponerine ant Leptogenys schwabi Forel 1913 has no morphologically or anatomically distinct reproductive castes and several mated workers in each colony, providing a model for the study of the effect(s) of polygyny on the social organization of a naturally queenless speci...

Cuticular hydrocarbons (CHCs) are used for chemical communication among nestmates in many ant species, and they may play a role in the discrimination of nestmates and non-nestmates. Using the mandible opening response (MOR) bioassay, we tested the response of the African termite raiding ant, Pachycondyla analis, to CHC extracts of nestmates and non...

Adverse environmental conditions can be evaded, tolerated or modified in order for an organism to survive. During their development, some insect larvae spin cocoons which, in addition to protecting their occupants against predators, modify microclimatic conditions, thus facilitating thermoregulation or reducing evaporative water loss. Silk cocoons...

The 10 fatty acid ester components of brood pheromone were extracted from larvae of different populations of USA and South African honey bees and subjected to gas chromatography-mass spectrometry quantitative analysis. Extractable amounts of brood pheromone were not significantly different by larval population; however, differences in the proportio...

To explore reasons for the unusually high rates of worker ovary activation in Apis cerana, we investigated the reproductive physiology of workers in conspecific and mixed-species colonies of A. cerana and its sibling species Apis mellifera under queenright and queenless conditions. In both queenless and queenright conspecific colonies, the proporti...

Although pollinator declines are a global biodiversity threat, the demography of the western honeybee (Apis mellifera) has not been considered by conservationists because it is biased by the activity of beekeepers. To fill this gap in pollinator decline censuses and to provide a broad picture of the current status of honeybees across their natural...

Honeybees are native to Africa and Europe but have been spread worldwide as the basis for an apicultural industry. To date, large and diverse wild populations only remain in Africa. On this continent the beekeeping industry is relatively undeveloped and relies on trapping swarms from wild populations to constitute the managed stocks. Bee breeding i...

The mating system of the honeybee (Apis mellifera) has been regarded as one of the most panmictic in the animal kingdom, with thousands of males aggregating in drone congregation areas (DCAs) that virgin queens visit to mate with tens of partners. Although males from many colonies gather at such congregations, the temporal changes in the colonies c...

Although tropical forest conservation is a top priority for human and environmental health, deforestation persists, mainly because of food and economic needs. No community will totally give up economic activities for the sake of ecological integrity, unless it is given alternative economic activities from which to draw its livelihood. Beekeeping in...

Estimating the population size of social bee colonies in the wild is often difficult because nests are highly cryptic. Because of the honeybee (Apis mellifera) mating behaviour, which is characterized by multiple mating of queens at drone congregation areas (DCA), it is possible to use genotypes of drones caught at these areas to infer the number o...

Terrestrial organisms need to limit evaporation from their bodies in order to maintain a homeostatic water balance. Owing to a large surface to volume ratio, arthropods are particularly susceptible to desiccation and have evolved behavioural and physiological mechanisms to conserve water. In social insects, water balance is also affected by the int...

Queen pheromones interfere with worker reproduction in social insects. However, there is still an unresolved question as to whether this pheromone acts as an “honest” signal for workers, giving a reliable indication of the queen’s reproductive value, or as a suppressive agent, inhibiting worker reproduction independent of the queen’s reproductive c...

The three Leptogenys species L.nitida, L.schwabi and L.attenuata coexist in the coastal forests of South Africa and exhibit an array of foraging strategies ranging from individual foraging to group raiding. To determine whether there is a physiological basis for these strategies, the energetic cost of locomotion of individuals in these three specie...

Contests mediate access to reproductive opportunities in almost all species of animals. An important aspect of the evolution of contests is the reduction of the costs incurred during intra-specific encounters to a minimum. However, escalated fights are commonly lethal in some species like the honeybee, Apis mellifera. By experimentally reducing hon...

The density of wild honeybee colonies (Apis mellifera) in the African dry highland savannahs was estimated in three Nature Reserves in Gauteng, South Africa (Ezemvelo, Leeuwfontein, Suikerbosrand) based on the genotypes of drones which were caught at drone congregation areas. Densities were estimated to range between 12.4 and 17.6 colonies per squa...

Differentiation into castes and reproductive division of labour are a characteristics of eusocial insects. Caste determination occurs at an early stage of larval development in social bees and is achieved via differential nutrition irrespective of the genotype. Workers are usually subordinate to the queen and altruistically refrain from reproductio...

The recent invasion by self-replicating socially parasitic Cape honeybee workers, Apis mellifera capensis, of colonies of the neighbouring African subspecies Apis mellifera scutellata represents an opportunity to study evolution of intraspecific parasitism in real time. As honeybee workers compete pheromonally for reproductive dominance, and as A....

Social parasites exploit their host’s communication system to usurp resources and reproduce. In the honeybee, Apis mellifera, worker reproduction is regulated by pheromones produced by the queen and the brood. Workers usually reproduce when the queen is removed and young brood is absent. However, Cape honeybee workers, Apis mellifera capensis, are...

Honeybee workers, Apis mellifera, can reproduce in queenless colonies. The production of queen-like pheromones may be associated with their reproductive activity and induce nestmates to respond by feeding them. Such frequent trophallaxis could supply their protein needs for oogenesis, constituting a social pathway to worker reproduction. However, s...

In colonies of the queenless ant Streblognathus peetersi, dominance interactions produce a reproductive hierarchy in which one individual, the alpha, is capable of producing offspring while her subordinates remain infertile. Based on differences between behaviour and cuticular hydrocarbon profiles, the subordinates can be further divided into high...

A single clonal lineage of socially parasitic Cape honeybee workers, Apis mellifera capensis, has caused dramatic losses in managed populations of A. m. scutellata, raising concerns that wild populations might also be affected. We surveyed A. m. scutellata swarms at 27 localities in beekeeping areas (N = 87) and in nature reserves (N = 79). While e...

Nest and nestmate recognition cues were investigated in the primitively social South African allodapine bee, Allodape rufogastra. Nest owners were able to distinguish between resident and non-resident bees, and engaged in significantly more agonistic interactions with non-residents. Combined GC-MS analysis of extract of head extracts showed it to c...

Workers of the honey bee subspecies Apis mellifera capensis (Eschscholtz) produce female offspring by thelytokous parthenogenesis and can parasitize colonies of other subspecies. In 1990, translocation of 400 colonies of A. m. capensis into the distribution area of A. m. scutellata by a commercial beekeeper triggered a dramatic parasitic phenomenon...