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LD2668 .T4 1954 M8 / Master of Science

The influence of foraging ants on the insect fauna within the canopy of the tree species Terminalia sericea, Burkea africana and Ochna pulchra was studied in an area of typical South African savanna, over a two year period. The number of individual insects and their species composition was compared on unbanded, ant-infested plants and on banded plants where ants had been excluded. Differences in the level of herbivory recorded on banded and unbanded trees were related to the guild composition of insects within the canopy, and the results are discussed in terms of plant protection as a consequence of ant - insect interactions. Twenty-six ant species were recorded on the study trees at Nylsvley, with individuals belonging to the genus Crematogaster being numerically abundant and dominant within the canopy of each species of tree. These dominant ant species influenced the insect fauna by their strong dependence on honeydew, encouraging a build up in numbers of Homoptera on the branches and leaves of foraged trees, and supporting homopterous populations within the confines of their nest compartments . The exclusion of ants from trees led to fewer "mobile" homopterans (Aphididae, Membracidae, Psyllidae and Cicadellidae) and "sessile" homopterans (mainly Coccidae but also Pseudococcidae). Pyrethrum spraying showed that the guild composition of non-homopterous insects was similar on banded and unbanded trees. Differences in the level of herbivory on banded and unbanded trees suggested that, although slight, foraged trees were protected from some damage by the presence of ant species within the canopy. A trend did exist towards a greater number of insect individuals and species on unbanded trees, and it is postulated that during the period 1982 1984 when drought conditions prevailed over Nylsvley, ants do not reduce insect numbers through predation or disturbance but simply deter phyllophagous feeding. A separate experiment showed that Crematogaster constructor would feed on the eggs and early instar larvae of the saturnid moth, Cirina forda, but low numbers of lepidopterous larvae on the trees may have forced ants to seek honeydew. The negative impact of large homopterous populations on foraged trees was only seen in an isolated field observation where Polyrachis schistacea was found to associate with the lac insect Tachardina sp . . In conclusion it can be said that where homopterans are not the dominant phyllophages, plants do benefit from foraging populations of ants in that damage to the leaves is reduced.

As flower visitors, ants rarely benefit a plant, commonly disrupting pollination by deterring other flower visitors, or stealing nectar. This thesis examines three aspects of ant-flower interactions, focusing on the occurrence of floral traits that prevent disruption of pollination and a novel means by which ants may influence pollinator behaviour. To assess which types of plant species possess ant-repelling floral traits I carried out a survey of 49 Neotropical plant species. Around a third of these species were repellent to the common generalist ant Camponotus novograndensis (Formicinae). This repellence was positively correlated with large nectar volumes within individual flowers. It appears that there has been selection for floral ant-repellence as a defence against ant thieves in plant species that invest in large volumes of nectar. In some cases these repellent traits were effective against a wide range of ant species. However, in no plant species were predacious ants particularly repelled, indicating that there may be little selective pressure on non-ant-plants to defend potential pollinators from aggressive ants. To investigate the importance of coevolution in determining the effectiveness of ant-repellents, a small but diverse range of Mediterranean plant species were tested with the invasive nectar thieving ant Linepithema humile (Dolichoderinae) and the native but non-nectar thieving ant Messor bouvieri (Myrmecinae). Responses of both ant species to floral traits were very similar. The ability of some plants to restrict access to ant species with which they have no evolutionary history may help to reduce the impact invasive species, as nectar thieves, have on plant-pollinator interactions. It is reported that flowers recently visited by bees and hoverflies may be rejected for a period of time by subsequent bee visitors through the detection of scent-marks. Nectar-thieving ants could potentially influence the foraging decisions of bees in a similar way if they come to associate ant trail pheromones or footprint hydrocarbons with poor reward levels. However, my empirical work found no differences were found in bee visitation behaviour between flowers of Digitalis pupurea (Plantaginaceae), Bupleurum fruticosum (Apiaceae) or Brassica juncea (Brassicaceae) that had been in contact with ants and control flowers. Ant-attendance at flowers of these species may not reduce reward levels sufficiently to make it worthwhile for bees to incorporate ant scent-marks into foraging decisions. Investigations like these into the interactions between ants, flowers and other flower visitors are essential if we hope to understand the part ants play in pollination ecology, and determine how ants have helped shape floral evolution.

by Xu Haoyu. / Thesis submitted in: July 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 89-95). / Abstracts in English and Chinese. / Acknowledgement --- p.i / Abstract --- p.ii / 摘要 --- p.iii / Contents --- p.iv / List of Abbreviations --- p.vii / List of Tables --- p.viii / List of Figures --- p.ix / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.1.1 --- Routing --- p.2 / Chapter 1.1.2 --- Ant Colony Optimization --- p.6 / Chapter 1.2 --- Research Statement --- p.8 / Chapter 1.3 --- Main Contributions --- p.10 / Chapter 1.4 --- Thesis Organization --- p.11 / Chapter Chapter 2 --- Ant Colony Optimization Routing --- p.12 / Chapter 2.1 --- ACO Routing Algorithms --- p.13 / Chapter 2.1.1 --- ACO Routing Algorithms in Circuit-Switched Networks --- p.13 / Chapter 2.1.2 --- ACO Routing Approaches in Packet-Switched Networks --- p.16 / Chapter 2.2 --- ACO Routing and Traditional Routing Algorithms --- p.23 / Chapter 2.3 --- ACO Routing and Optimal Routing Algorithms --- p.26 / Chapter Chapter 3 --- Reactive Ant Colony Optimization --- p.31 / Chapter 3.1 --- Problem Model --- p.31 / Chapter 3.2 --- RACO Routing Approach --- p.35 / Chapter 3.2.1. --- Node and Probabilistic Routing Table --- p.36 / Chapter 3.2.2. --- Ants --- p.38 / Chapter 3.2.3 --- Detailed Description of RACO routing approach --- p.43 / Chapter Chapter 4 --- Simulation Results --- p.45 / Chapter 4.1 --- Experiment Design --- p.45 / Chapter 4.1.1 --- Topology --- p.46 / Chapter 4.1.2 --- Network Layers --- p.48 / Chapter 4.2 --- Results --- p.50 / Chapter 4.2.1 --- NSFNET --- p.50 / Chapter 4.2.2 --- ARPANET --- p.52 / Chapter 4.3 --- Discussion --- p.53 / Chapter Chapter 5 --- Convergence Analysis --- p.58 / Chapter 5.1. --- Related Work --- p.59 / Chapter 5.2 --- "Two-Node, Two-Path Model" --- p.61 / Chapter 5.3 --- The Recursive Pheromone Values --- p.64 / Chapter 5.4 --- Pheromone Convergence --- p.70 / Chapter 5.5 --- General Models --- p.81 / Chapter 5.5.1 --- "Two - Node, N - Path Model" --- p.81 / Chapter 5.5.2 --- "M- Node, N(i.j) - Path Model" --- p.83 / Chapter 5.6. --- Conclusion and Discussion --- p.84 / Chapter Chapter 6 --- Conclusion and Future Work --- p.86 / Chapter 6.1 --- Conclusion --- p.86 / Chapter 6.2 --- Future Work --- p.87 / Reference --- p.89 / Appendices --- p.96 / "Appendix 1 The Detailed Form of P = f1（a,b) and Q = f2（a,b)" --- p.96 / "Appendix 2 To Validate Whether f1（a,b) in the Domain of (0,1)" --- p.102

Orientador: Luiz Carlos Forti / Coorientador: Juliane Floriano Lopes Santos / Banca: Pedro Leite Ribeiro / Banca: Vânia Maria Ramos / Banca: Roberto da Silva Camargo / Banca: Ivone Paschoal Garcia / Resumo: Não disponível / Abstract: Not available / Doutor

Ants are fascinating creatures - not so much because they are intelligent on their own, but because as a group they display compelling emergent behaviour (the extent to which one observes features in a swarm which cannot be traced back to the actions of swarm members). What does each swarm member do which allows deliberate engineering of emergent behaviour? We investigate the development of a language for programming swarms of ant agents towards desired emergent behaviour. Five aspects of stigmergic (pheromone sensitive computational devices in which a non-symbolic form of communication that is indirectly mediated via the environment arises) and message passing ant agents (computational devices which rely on implicit communication spaces in which direction vectors are shared one-on-one) are studied. First, we investigate the primitive behaviours which characterize ant agents' discrete actions at individual levels. Ten such primitive behaviours are identified as candidate building blocks of the ant agent language sought. We then study mechanisms in which primitive behaviours are put together into XSets (collection of primitive behaviours, parameter values, and meta information which spells out how and when primitive behaviours are used). Various permutations of XSets are possible which define the search space for best performer XSets for particular tasks. Genetic programming principles are proposed as a search strategy for best performer XSets that would allow particular emergent behaviour to occur. XSets in the search space are evolved over various genetic generations and tested for abilities to allow path finding (as proof of concept). XSets are ranked according to the indices of merit (fitness measures which indicate how well XSets allow particular emergent behaviour to occur) they achieve. Best performer XSets for the path finding task are identifed and reported. We validate the results yield when best performer XSets are used with regard to normality, correlation, similarities in variation, and similarities between mean performances over time. Commonly, the simulation results yield pass most statistical tests. The last aspect we study is the application of best performer XSets to different problem tasks. Five experiments are administered in this regard. The first experiment assesses XSets' abilities to allow multiple targets location (ant agents' abilities to locate continuous regions of targets), and found out that best performer XSets are problem independent. However both categories of XSets are sensitive to changes in agent density. We test the influences of individual primitive behaviours and the effects of the sequences of primitive behaviours to the indices of merit of XSets and found out that most primitive behaviours are indispensable, especially when specific sequences are prescribed. The effects of pheromone dissipation to the indices of merit of stigmergic XSets are also scrutinized. Precisely, dissipation is not causal. Rather, it enhances convergence. Overall, this work successfully identify the discrete primitive behaviours of stigmergic and message passing ant-like devices. It successfully put these primitive behaviours together into XSets which characterize a language for programming ant-like devices towards desired emergent behaviour. This XSets approach is a new ant language representation with which a wider domain of emergent tasks can be resolved.

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Orientadores: Paulo Sergio Moreira Carvalho de Oliveira, Andre Victor Lucci Freitas / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T07:47:45Z (GMT). No. of bitstreams: 1 Moraes_AliceRamosde_M.pdf: 978814 bytes, checksum: c7ab335564cf485af296179b41d1ca80 (MD5) Previous issue date: 2006 / Resumo: 1. O presente trabalho investiga aspectos comportamentais e de história natural de duas espécies de lepidópteros que se alimentam de Urera baccifera (Urticaceae), uma planta visitada por 22 espécies de formigas. Ambas as espécies, Pleuroptya silicalis (Lepidoptera: Crambidae) e Urbanus esmeraldus (Lepidoptera: Hesperiidae), constróem abrigos foliares e apresentam diferentes mecanismos de defesa contra predação. Por exemplo, quando perturbadas, larvas de P. silicalis sacodem o corpo violentamente, jogam-se da folha, mordem e regurgitam. Larvas de U. esmeraldus mordem e regurgitam, apenas. Ambas as espécies preferem folhas maduras, passam por cinco estádios de desenvolvimento e apresentam características comuns a outros membros de suas famílias. 2. Pleuroptya silicalis constrói abrigos foliares em forma de tubo, enchendo-os com seda e fezes, sendo comum encontrar vários indivíduos no mesmo abrigo. Já Urbanus esmeraldus constrói dois tipos de abrigos foliares ao longo de seu desenvolvimento e apenas uma larva é encontrada em cada abrigo. 3. Abrigos foliares artificiais, similares aos abrigos de P. silicalis (porém sem fezes ou seda dentro) não fornecem proteção a cupins, usados como herbívoros simulados. As fezes também não provocam mudanças de comportamento em formigas no laboratório, não as atraindo aos abrigos ou repelindo dos mesmos. As fezes podem, entretanto, funcionar como barreira mecânica, dificultando o acesso ao interior do abrigo. 4. Urbanus esmeraldus lança suas fezes a grandes distâncias. Experimentos demonstraram que fezes no chão induzem formigas a subirem na planta hospedeira. Por outro lado, fezes arremessadas longe da base da planta não produzem o mesmo efeito. Além disso, larvas de 5º estádio cortam o pecíolo das folhas em que descansam, e das quais se alimentam, tornando-as murchas precocemente. Uma vez que formigas conseguem transpor o pecíolo cortado, este comportamento pode estar relacionado à redução de predação por aves, já que estas podem utilizar sinais visuais indicativos de presença e/ou atividade de lagartas no forrageamento. O corte do pecíolo pode ainda reduzir o parasitismo das larvas (prejudicando a transmissão de vibrações provenientes da lagarta e dificultando a ação de parasitóides que dependam deste tipo de sinal para localização do hospedeiro), ou mesmo acelerar a eliminação de compostos secundários da planta. Tais hipóteses, entretanto, precisariam ser testadas. 5. Durante o ano de 2006, a presença de formigas não foi suficiente para diminuir a infestação por todas as espécies de lepidópteros de Urera baccifera, ao contrário do observado em anos anteriores (2003 e 2004). Esta variação temporal pode ser explicada por uma diferença na abundância dos herbívoros (mais abundantes em 2006), determinando assim o nível de sucesso das formigas na proteção à planta / Abstract: 1. This work investigates the biology and behaviour of two lepidopteran species that feed on the nettle Urera baccifera (Urticaceae). The plant is visited by 22 ant species, which are attracted by the nettle's fleshy fruits and pearl bodies. Larvae of both species build leaf shelters: Pleuroptya silicalis (Crambidae: Pyraustinae) makes leaf rolls, and Urbanus esmeraldus (Hesperiidae: Pyrginae) builds two different kinds of shelters (peaked-roof shelters and leaf folds). Both species have 5 instars of development and present morphological and behavioural similarities to other members in each of their families. 2. Larvae of P. silicalis fill the leaf rolls with silk and faeces (frass). Artificial rolls, very similar in shape and size, but without silk or frass, did not prevent termite workers glued on the inside from being preyed by ants. Although frass did not alter the behaviour of ant foragers in the laboratory, faecal pellets could play an important role against predators and parasitoids by mechanically preventing them from entering the roll. 3. Larvae of Urbanus esmeraldus throw their faecal pellets at great distances. We experimentally demonstrated that frass located near the base of an artificial shrub induce foraging ants to climb on the plant in greater numbers than faecal pellets 30 cm away from the plant. Thus frass ejection influences directly larval vulnerability to ants. 4. Fifth-instar larvae of U. esmeraldus cut the petiole of the leaves they rest and feed. Ants, however, are not deterred by the cut petiole and it is suggested that this larval behaviour could be related with avian predation pressure. Because the cut leaves soon wither, the visual effect can be deceptive for insectivorous birds that tend to forage more often on healthy leaves. Alternatively, cutting the leaf could reduce the plant¿s secondary compounds, or decrease attack by parasitoids that use leafborne vibrations to locate their hosts. 5. In 2006 ant presence did not affect infestation by lepidopteran larvae on U.baccifera shrubs. Although ants have been reported by other authors to decrease caterpillar infestation in previous years, at increased herbivore abundance ant visitation may not be sufficient to suppress caterpillars on hostplants / Mestrado / Mestre em Ecologia

L’exploitation collective de ressources par les sociétés animales repose sur la coopération et la coordination des membres du groupe. Selon la structure sociale des espèces envisagées, leurs comportements collectifs seront dictés par quelques individus imposant leurs choix ou au contraire impliqueront tous les membres du groupe. Chez la fourmi Tetramorium caespitum, la récolte de nourriture repose à la fois sur le dépôt d’une piste de phéromone chimique commune lors du retour des ouvrières vers le nid et sur le recrutement de groupe de congénères guidés par des individus leaders jusqu’à la source de nourriture. Cette espèce nous donne donc l’opportunité d’étudier un système de recrutement couplant des mécanismes décentralisés à la présence d’individus leaders.<p>Nos observations montrent que le recrutement de groupe est lié à une forte motivation de certaines ouvrières à exploiter une source de nourriture découverte. Lorsqu’elles recrutent un groupe, elles passent peu de temps à l’intérieur du nid mais effectuent un taux élevé de contacts avec leurs congénères, principalement à l’entrée du nid, avant de repartir en direction de la nourriture, suivie par le peloton de fourrageuses. Durant le trajet, si une trajectoire rectiligne et une faible vitesse de déplacement favorisent la probabilité des recrutées d’atteindre la source, la perte de recrutées n’entraîne cependant aucune modification du comportement de la meneuse. Enfin, un suivi individualisé des fourrageuses au cours du recrutement montre que la probabilité d’être observée en tant que leader est répartie de manière homogène entre les individus découvrant la source de nourriture, sans influence du nombre de trajets qu’elles ont déjà effectués.<p>Par ailleurs, nous avons étudié l’influence des leaders sur les choix collectifs de la colonie. Les leaders modulent les caractéristiques du recrutement -­-fréquence des groupes, tailles des groupes-­- en fonction des caractéristiques de la source exploitée. Grâce à un modèle multi-­-agents, nous avons démontré que cette modulation du recrutement permet à la colonie entière de focaliser son effort d’affourragement sur la nourriture la plus avantageuse lorsque plusieurs sources sont disponibles dans l’environnement. Enfin, nous avons développé un modèle mathématique décrivant le couplage du recrutement de groupe et du dépôt d’une piste chimique. Grâce à l’étude des états stationnaires de ce modèle, nous avons démontré que la présence des leaders est un élément indispensable à l’initiation de l’exploitation collective d’une ressource chez T. caespitum. Ainsi, les leaders de groupe permettent d’atteindre plus aisément un nombre seuil d’ouvrières à la source qui soit suffisant pour permettre l’émergence d’une piste chimique commune assurant à elle seule un recrutement de masse. Les résultats de cette thèse placent dans une nouvelle perspective notre vision des phénomènes de leadership chez les insectes sociaux. A l’échelle individuelle, ils mettent en évidence le statut temporaire de ces leaders chez Tetramorium caespitum basé sur leur propre motivation et les conditions locales du recrutement ;à l’échelle collective, ils soulignent le rôle complémentaire et facilitateur des leaders qui vont permettre l’émergence de structures auto-­- organisées impliquant l’ensemble de la fourmilière. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished