abstract: The coordination of group behavior in the social insects is representative of a broader phenomenon in nature, emergent biological complexity. In such systems, it is believed that large-scale patterns result from the interaction of relatively simple subunits. This dissertation involved the study of one such system: the social foraging of the ant Temnothorax rugatulus. Physically tiny with small population sizes, these cavity-dwelling ants provide a good model system to explore the mechanisms and ultimate origins of collective behavior in insect societies. My studies showed that colonies robustly exploit sugar water. Given a choice between feeders unequal in quality, colonies allocate more foragers to the better feeder. If the feeders change in quality, colonies are able to reallocate their foragers to the new location of the better feeder. These qualities of flexibility and allocation could be explained by the nature of positive feedback (tandem run recruitment) that these ants use. By observing foraging colonies with paint-marked ants, I was able to determine the `rules' that individuals follow: foragers recruit more and give up less when they find a better food source. By altering the nutritional condition of colonies, I found that these rules are flexible - attuned to the colony state. In starved colonies, individual ants are more likely to explore and recruit to food sources than in well-fed colonies. Similar to honeybees, Temmnothorax foragers appear to modulate their exploitation and recruitment behavior in response to environmental and social cues. Finally, I explored the influence of ecology (resource distribution) on the foraging success of colonies. Larger colonies showed increased consistency and a greater rate of harvest than smaller colonies, but this advantage was mediated by the distribution of resources. While patchy or rare food sources exaggerated the relative success of large colonies, regularly (or easily found) distributions leveled the playing field for smaller colonies. Social foraging in ant societies can best be understood when we view the colony as a single organism and the phenotype - group size, communication, and individual behavior - as integrated components of a homeostatic unit. / Dissertation/Thesis / Ph.D. Biology 2014

The 1883 discovery, research into generic life histories and taxonomic investigations into the aphytophagous butterfly Thestor brachycerus brachycerus (the Knysna Skolly) from Knysna, South Africa are described. Its slide towards extinction through loss and degradation of habitat in the late 20th century left only one known colony by 2009 leading to it being assessed as Critically Endangered in the 2013 South African Red List and Atlas. During searches for more populations in 2011, a second T. b. brachycerus colony was found which differed markedly with respect to aspect, altitude and vegetation. Study areas were defined around the original colony on the Pezula Golf Estate (Pezula) and the newly discovered coastal colony east of Coney Glen (Coastal site). An assessment is made of the ecological differences and similarities between the two sites. The extent and size of the two known populations was measured; the Extent of Occupancy was found to be 7.5 km2 and the Area of Occupancy as 1.05 x 10-3 km2. During observations over 5 seasons in December and January 2009 – 2014 the average number of butterflies observed at the original Pezula colony varied from 1 – 8 males and 0 – 3 females per survey, compared with 1 – 6 males and 1 – 3 females observed over 3 seasons from 2011 to 2014 at the Coastal colony. The mating, territoriality, oviposition and predation avoidance behaviour of the adult T. b. brachycerus butterflies was studied by direct observation. Males were found to exhibit territorial behaviour, spending long periods of time perched in one spot, particularly in areas where the vegetation was open or low. Oviposition was rapid and no preference was shown by females for any particular plant. Between the two colonies, oviposition was observed on a total of 16 different plants. The vegetation composition at the two study sites was analysed using Braun–Blanquet methodology. Only one plant, Tarchonanthus littoralis, was found to be common to both. There appeared to be no correlation between floristic composition and the occurrence of T. b. brachycerus. All the Thestor species so far studied by other workers have been found to be myrmecophilous, having an association with the pugnacious ant Anoplolepis custodiens. Ant communities were sampled by employing pitfall traps and direct sampling by hand. At both the Pezula and Coastal sites A. custodiens was the most ubiquitous ant species. The insights gained have enabled implementation of a habitat management plan. Experimental management methods are recommended at the Pezula site which include small scale burning and selective cutting of vegetation. Search for more colonies is ongoing, using the improved ecological knowledge of the butterfly. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The 1883 discovery, research into generic life histories and taxonomic investigations into the aphytophagous butterfly Thestor brachycerus brachycerus (the Knysna Skolly) from Knysna, South Africa are described. Its slide towards extinction through loss and degradation of habitat in the late 20th century left only one known colony by 2009 leading to it being assessed as Critically Endangered in the 2013 South African Red List and Atlas. During searches for more populations in 2011, a second T. b. brachycerus colony was found which differed markedly with respect to aspect, altitude and vegetation. Study areas were defined around the original colony on the Pezula Golf Estate (Pezula) and the newly discovered coastal colony east of Coney Glen (Coastal site). An assessment is made of the ecological differences and similarities between the two sites. The extent and size of the two known populations was measured; the Extent of Occupancy was found to be 7.5 km2 and the Area of Occupancy as 1.05 x 10-3 km2. During observations over 5 seasons in December and January 2009 – 2014 the average number of butterflies observed at the original Pezula colony varied from 1 – 8 males and 0 – 3 females per survey, compared with 1 – 6 males and 1 – 3 females observed over 3 seasons from 2011 to 2014 at the Coastal colony. The mating, territoriality, oviposition and predation avoidance behaviour of the adult T. b. brachycerus butterflies was studied by direct observation. Males were found to exhibit territorial behaviour, spending long periods of time perched in one spot, particularly in areas where the vegetation was open or low. Oviposition was rapid and no preference was shown by females for any particular plant. Between the two colonies, oviposition was observed on a total of 16 different plants. The vegetation composition at the two study sites was analysed using Braun–Blanquet methodology. Only one plant, Tarchonanthus littoralis, was found to be common to both. There appeared to be no correlation between floristic composition and the occurrence of T. b. brachycerus. All the Thestor species so far studied by other workers have been found to be myrmecophilous, having an association with the pugnacious ant Anoplolepis custodiens. Ant communities were sampled by employing pitfall traps and direct sampling by hand. At both the Pezula and Coastal sites A. custodiens was the most ubiquitous ant species. The insights gained have enabled implementation of a habitat management plan. Experimental management methods are recommended at the Pezula site which include small scale burning and selective cutting of vegetation. Search for more colonies is ongoing, using the improved ecological knowledge of the butterfly. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The distribution of resources is vital to any system or society. This is particularly true of social insect colonies where independent access to resources is not available to all members. Only a fraction of individuals are responsible for obtaining food for the colony from outside the nest. Surprisingly little is known about how this food is subsequently distributed to members inside the nest. The work in this thesis is focused around a set of food distribution experiments conducted using four colonies of the ant Temnothorax albipennis. The study applies a well-used technique in a new way to investigate the distribution of food under two different scenarios: feeding under normal conditions and famine relief feeding after a period of starvation. All ants in each colony are marked and then individually tracked recording every feeding interaction to obtain a complete network of food transmission. This work has shown that all four colonies efficiently relieved the famine within 30 minutes of introducing new food. This process was facilitated by workers abandoning their spatial structure and expanding their space use; feeding multiple recipients from a single donor; and simultaneously spreading stored food and new food. Recruitment of foragers did not play a major role in relieving the famine but foragers were responsible for most of the first round of feeding. The study revealed that not all members received the same amount of food and most ants received food in multiple feeding interactions. The transmission pathways used to distribute the food present an opportunity for harmful substances to spread. The pathways are explored in this context to see whether the colonies might aim to minimize the spread by partitioning the pathways or maximise spread by mixing to promote social immunity. The study reveals behavioural differences between the four colonies which are likely to result from the inherent variation in demographic and geometric properties. These differences highlight the flexibility of ant colonies during problem solving under different conditions.

No description available.

Les interactions entre individus sont un socle vital pour l’organisation des colonies d’abeilles, en particulier lors du recrutement pour le butinage. Outre la communication de la localisation d’une source de nourriture par la fameuse danse, les abeilles recrutées apprennent les caractéristiques de l’odeur des fleurs butinées au cours de transferts de nectar (trophallaxie). Les mécanismes de cet apprentissage ne sont pas encore éclaircis car il est parfois effectif sans aucun transfert de nectar, suggérant que d’autres mécanismes, comme par exemple d’apprentissage social, sont impliqués. Nous avons reproduit cette interaction en laboratoire, suivant un protocole basé sur le conditionnement olfactif appétitif de la réponse d’extension du proboscis (REP). Ici, un composé odorant initialement neutre (Stimulus conditionnel) était associé à un contact avec une congénère (Stimulus Inconditionnel social), sans récompense sucrée. Nos expériences montrent que ce simple contact social entre congénères peut constituer un renforcement pour les abeilles. A la suite de cette association, celles-ci montrent donc des REP à l’odeur préalablement associée au contact social. Nos expériences montrent de plus que des contacts antennaires entre les abeilles sont indispensables à l’efficacité de cet apprentissage social, représentant un indice social tactile. Nous avons alors développé un dispositif permettant d’enregistrer les mouvements des antennes de manière précise et à haute vitesse (90 hz) et étudié les différents facteurs modulant les mouvements antennaires des abeilles. Les abeilles montrent des réponses contrastées et reproductibles à des odeurs de valeurs biologiques différentes. De plus, le couplage de ces enregistrements à des expériences de conditionnement associatif montre que ces réponses antennaires sont plastiques et modifiées par l’expérience des individus. Ce travail a permis de mettre en lumière un nouveau type d’apprentissage social chez les insectes et d’approfondir l’étude des mouvements antennaires comme indicateurs de l’état motivationnel, attentionnel et physiologique des abeilles ainsi que de la valence des stimuli perçus. / In honeybees, interactions between individuals are cornerstones for the organization of the colony, especially during recruitment for foraging. Besides learning the location of a food source thanks to the well-known dance, the recruited bees learn the characteristics of odors of foraged flowers through nectar transfer (trophallaxis). The underlying mechanisms are still unclear because this learning can occur without any nectar transfer, suggesting that other, probably social, learning mechanisms are involved. We reproduced this interaction in the lab, using a protocol based on the appetitive olfactory conditioning of the proboscis extension response (PER). Here, an initially neutral odorant (conditioned stimulus) was associated with a contact with a nestmate (social unconditioned stimulus), without any sugar reward. Our experiments show that this simple social contact between workers can act as a reinforcement for bees. As a result, they show PER to the odor previously associated with a social contact. We further demonstrate that antenna contacts are essential for the effectiveness of this social learning, representing a tactile social cue. We thus developed a system allowing to record bees’ antennal movements accurately and at high frequency (90 hz). We then determined the factors modulating bees’ antennal movements. First, we show that bees display contrasted and reproducible responses to odors of different biological values. Second, the coupling of these recordings with associative conditioning experiments shows that these antennal responses are plastic and modified by individual experience. This work has shed light on a new type of social learning in insects and has furthered our understanding of antennal movements as indicators of the motivational, attentional and physiological state of bees and of the valence of perceived stimuli.