Ce travail est dédié à l'étude du comportement agrégatif chez la fourmi Lasius niger afin de caractériser le phénomène au niveau collectif, par l'étude de la dynamique et de la structure agrégative, et au niveau des mécanismes sous-tendant le phénomène par l’analyse des comportements individuels des fourmis. Nous avons montré expérimentalement et vérifié par la modélisation que l’agrégation est essentiellement liée à un phénomène amplificateur : plus l’agrégat est de grande taille, plus les fourmis y restent longtemps. Nos résultats indiquent que le niveau d’agrégation et la structure formée sont dépendants de plusieurs facteurs comme la densité et la surface disponible : une évolution de la structure agrégative des nourrices est observée, passant d’un grand agrégat stable pour les petites densité-surface à plusieurs agrégats à hiérarchie de taille moins marquée pour les grandes densité-surface. L’agrégation est aussi influencée par la caste éthologique des fourmis, les nourrices s’agrégeant en un agrégat stable de grande taille, les fourrageuses en quelques petits agrégats instables. Cette différence s’explique par une probabilité plus faible des fourrageuses à rester dans l’agrégat. Dans les groupes mixtes, les fourmis gardent les caractères propres à leur caste, ne semblant pas influencées par la caste de l’individu rencontré. Enfin, l’agrégation diffère quantitativement mais non qualitativement selon l’espèce utilisée : nos études sur Crematogaster scutellaris, Atta sexdens-rubropilosa, Solenopsis invicta, Pheidole pallidula, Linepithema humile, Myrmica rubra et M. ruginodis montrent une grande variété de réponses, en nombre et en taille d’agrégats, qui est aussi fonction de la caste de fourmis utilisée. Une constance, cependant, apparaît dans nos résultats : les nourrices paraissent mieux s’agréger que les fourrageuses. Ces résultats sont discutés en fonction de leur valeur adaptative pour la colonie et d’un lien possible avec la distribution spatiale des individus à l’intérieur du nid./This work is dedicated to the study of the aggregative behaviour in the ant Lasius niger in order to characterize the phenomenon at the collective level by a study of the dynamic and the collective structure, and at the individual level to understand the mechanisms underlying the phenomenon. We demonstrated experimentally and verified by a model that aggregation is essentially due to an amplificatory phenomenon: the greater the ant numbers in a cluster, the greater the time spent by an ant inside this cluster. Our results indicate that the aggregation level and the form of the collective structure depend on different factors such as the density and the surface: for brood-tenders, an evolution of the aggregative structure is observed shifting from a large stable aggregate for low density-surface to several smaller clusters with a less pronounced hierarchical size for the greater density-surface. Aggregation is also influenced by the ethological caste of the ant: the brood-tenders aggregate in a big stable cluster and the foragers in some unstable clusters. This difference is explained by a smaller probability of foragers to stay inside the cluster. In mixed groups, ants keep their own characteristics, not appearing to be influenced by the caste of the individual encountered. Finally, aggregation is influenced by the ant species: our studies on Crematogaster scutellaris, Atta sexdens-rubropilosa, Solenopsis invicta, Pheidole pallidula, Linepithema humile, Myrmica rubra and M. ruginodis show us a large variety of responses, in the number and the size of the clusters, which is also a function of the caste of ants which is used. A constant result, nevertheless, appears in our results: brood-tenders seem to aggregate better than foragers. These results are discussed in term of their adaptive value for the colony and a possible link with the spatial distribution of ants inside the nest.

O desempenho das atividades na colônia de abelhas Apis mellifera está relacionado com o funcionamento do sistema de glândulas que as abelhas possuem. No entanto, a presença de patógenos na população pode causar alterações comportamentais que prejudicam o bom desenvolvimento da colônia. O trabalho objetivou verificar se há relação entre a secreção proteica glandular e cerebral nas diferentes atividades desempenhadas por operárias adultas, em A. m. scutellata (Africanizada) e A. m. ligustica (Europeia), e como o vírus deformador de asas (DWV) poderia interferir no desempenho dessas atividades. Foram realizados: testes de proteínas pelo método Bradford no cérebro e nas glândulas salivar torácica, salivar cefálica, mandibular e hipofaríngea de abelhas Africanizadas e Europeias com idades de 0 (recém-emergidas), 5, 10, 15, 20, 25 e 30 dias; medição da área dos acinos das glândulas salivar cefálica e hipofaríngea dessas abelhas; avaliação do desenvolvimento de atividade realizada pelas abelhas e reversão do processo de oviposição por operárias em abelhas Africanizadas; teste para a presença do DWV por PCR em tempo real, em abelhas Africanizadas e em cérebro e glândulas salivar torácica, salivar cefálica, mandibular e hipofaríngea em abelhas Europeias com 5 e 30 dias de idade; e avaliação morfológica dos danos causados pela infecção aguda do DWV no cérebro e glândulas estudadas. As abelhas Africanizadas e Europeias apresentaram teores estatisticamente significativos de proteínas (p>0,05) para todas as estruturas e idades estudadas. As áreas dos acinos das glândulas salivar cefálica e hipofaríngea apresentaram alterações de acordo com o desenvolvimento dessas glândulas nas diferentes idades estudadas. Foi observado que enxames de abelhas de mesma idade são capazes de executar diferentes atividades necessárias para a sobrevivência de sua colônia, sendo que a principal atividade, desempenhada nas diferentes idades estudadas, era indicada pelos teores significativos de proteínas encontrados (p>0,05). As abelhas Europeias de mesma idade apresentaram desenvolvimento dos acinos da glândula salivar cefálica superior ao dos acinos da hipofaríngea nas idades iniciais avaliadas, diferindo da área dos acinos das mesmas glândulas quando comparadas com abelhas que tiveram o seu desenvolvimento em colônia normal. As operárias podem controlar o estado zanganeiro da colônia. As abelhas Africanizadas e Europeias apresentaram resultados positivos para o vírus DWV, resultado também observado nas glândulas salivar torácica e mandibular das abelhas com cinco dias de idade. Foi observado que a infecção aguda do DWV causa alterações morfológicas nas glândulas das abelhas,as quais apresentam plasticidade no desenvolvimento das atividades, não sendo estas restritas a uma determinada idade. Além disso, a infecção pelo vírus DWV não é limitante em abelhas Africanizadas, mas é em Europeias. / The performance of tasks in the Apis mellifera colony is related to the functioning of their gland system. However, the presence of pathogens in the population may lead to behavior modifications that can harm the proper development of the colony. This work aimed to verify whether there is relation between gland and brain protein secretion for the different tasks performed by the adult worker honeybees, in A. m. scutellata (Africanized) and A. m. ligustica (European), and how the deformed wing virus (DWV) could interfere with the performance of these tasks. The following analysis were carried out: protein tests (Bradford method) in the brain and in mandibular, hypopharyngeal, and thoracic and cephalic salivary glands, in Africanized and European honeybees at the ages of 0 (newborn), 5, 10, 15, 20, 25 and 30 days; measurements of the acini area of cephalic salivary and hypopharyngeal glands in those honeybees; evaluation of the development of tasks performed by honeybees and reversion of the laying workers of Africanized honeybees; test to detect DWV using real-time PCR in Africanized honeybees and in the brain and in mandibular, hypopharyngeal, and thoracic and cephalic salivary glands of European honeybees at the ages of 5 and 30 days; and morphological evaluation of the damages caused by the DWV acute infection in the brain and in the studied glands. Africanized and European honeybees showed statistically significant protein contents (p>0.05) for all the structures and ages studied. The acini areas of cephalic salivary and hypopharyngeal glands showed modifications according to the development of those glands at the different studied ages. It was observed that the swarms of bees with the same age are capable to perform different tasks needed to the survival of their colony, being the principal task, performed at the different studied ages, indicated by the significant protein contents found (p>0.05). The European honeybees at the same age showed higher acini development in the cephalic salivary gland than in the hypopharyngeal one at the initial studied ages, differing from the acini area in the same glands of honeybees grown in a regular colony. The worker honeybees can control the laying workers of the colony. Africanized and European honeybees showed positive results for DWV, which was also observed in thoracic salivary and mandibular glands in five-day-old honeybees. It was observed that the acute DWV infection causes morphological modifications in the honeybees glands, which show plasticity in the performance of tasks, not being them restricted to a particular age. Moreover, the DWV infection is not limiting for Africanized honeybees, but it is for the European ones.

A formação, recrutamento e manutenção de trilhas em formigas cortadeiras do gênero Atta é controlada quimicamente e envolve a participação de diferentes castas. Todavia, são escassos os estudos sobre a dinâmica das castas sob diferentes fontes de estímulos para a colônia, e como isso interfere na deposição de trilhas químicas. O presente trabalho visou compreender a influência de diferentes fontes de estímulos no padrão químico de deposição das trilhas, bem como no comportamento de recrutamento, forrageamento e defesa das operárias em Atta sexdens rubropilosa (Hymenoptera: Formicidae). Os resultados indicaram que houve variação do perfil etológico e alocação de tarefas desempenhadas pelos indivíduos presentes na colônia, de acordo com a fonte de estímulo. Neste caso foram oferecidos uma fonte de estímulo atrativa (\"pétalas de rosas\") e outra de agressividade (\"rainha de outra colônia\"). Além disso, os perfis químicos observados nas trilhas variaram qualitativamente e quantitativamente de acordo com os estímulos oferecidos. Estes dados sugerem que as operárias de A. sexdens rubropilosa seriam capazes de manejar quimicamente seu feromônio de trilha para informar e alterar o comportamento de suas companheiras de ninho, de acordo com a fonte de estímulo em que foram expostas. / Formation, recruitment and maintenance of trail in Atta leaf-cutting ants are chemically controlled and involve participation of different castes. Nevertheless, studies on caste dynamic under different stimuli to the colony are scarce, and how it interferes in the chemical deposition of the trail. This investigation aimed to understand how different source of stimuli influence the chemical pattern of trail marking as well as the recruitment, foraging and defense behavior by workers in Atta sexdens rubropilosa (Hymenoptera: Formicidae). Results indicate variation in the ethological profile and task allocation performed by the colony individuals, according to the stimuli source. In this case, it was offered an attractive stimulus source (\"rose petals\") and an aggressive one (\"other colony queen\"). Moreover, the chemical profiles of the trail varied qualitatively and quantitatively in response to the stimuli they were exposed. These data suggest that A. sexdens rubropilosa workers would be able to chemically manipulate their trail pheromone with aim to inform and alter their nestmate behavior in response to the exposed stimuli source.

O desempenho das atividades na colônia de abelhas Apis mellifera está relacionado com o funcionamento do sistema de glândulas que as abelhas possuem. No entanto, a presença de patógenos na população pode causar alterações comportamentais que prejudicam o bom desenvolvimento da colônia. O trabalho objetivou verificar se há relação entre a secreção proteica glandular e cerebral nas diferentes atividades desempenhadas por operárias adultas, em A. m. scutellata (Africanizada) e A. m. ligustica (Europeia), e como o vírus deformador de asas (DWV) poderia interferir no desempenho dessas atividades. Foram realizados: testes de proteínas pelo método Bradford no cérebro e nas glândulas salivar torácica, salivar cefálica, mandibular e hipofaríngea de abelhas Africanizadas e Europeias com idades de 0 (recém-emergidas), 5, 10, 15, 20, 25 e 30 dias; medição da área dos acinos das glândulas salivar cefálica e hipofaríngea dessas abelhas; avaliação do desenvolvimento de atividade realizada pelas abelhas e reversão do processo de oviposição por operárias em abelhas Africanizadas; teste para a presença do DWV por PCR em tempo real, em abelhas Africanizadas e em cérebro e glândulas salivar torácica, salivar cefálica, mandibular e hipofaríngea em abelhas Europeias com 5 e 30 dias de idade; e avaliação morfológica dos danos causados pela infecção aguda do DWV no cérebro e glândulas estudadas. As abelhas Africanizadas e Europeias apresentaram teores estatisticamente significativos de proteínas (p>0,05) para todas as estruturas e idades estudadas. As áreas dos acinos das glândulas salivar cefálica e hipofaríngea apresentaram alterações de acordo com o desenvolvimento dessas glândulas nas diferentes idades estudadas. Foi observado que enxames de abelhas de mesma idade são capazes de executar diferentes atividades necessárias para a sobrevivência de sua colônia, sendo que a principal atividade, desempenhada nas diferentes idades estudadas, era indicada pelos teores significativos de proteínas encontrados (p>0,05). As abelhas Europeias de mesma idade apresentaram desenvolvimento dos acinos da glândula salivar cefálica superior ao dos acinos da hipofaríngea nas idades iniciais avaliadas, diferindo da área dos acinos das mesmas glândulas quando comparadas com abelhas que tiveram o seu desenvolvimento em colônia normal. As operárias podem controlar o estado zanganeiro da colônia. As abelhas Africanizadas e Europeias apresentaram resultados positivos para o vírus DWV, resultado também observado nas glândulas salivar torácica e mandibular das abelhas com cinco dias de idade. Foi observado que a infecção aguda do DWV causa alterações morfológicas nas glândulas das abelhas,as quais apresentam plasticidade no desenvolvimento das atividades, não sendo estas restritas a uma determinada idade. Além disso, a infecção pelo vírus DWV não é limitante em abelhas Africanizadas, mas é em Europeias. / The performance of tasks in the Apis mellifera colony is related to the functioning of their gland system. However, the presence of pathogens in the population may lead to behavior modifications that can harm the proper development of the colony. This work aimed to verify whether there is relation between gland and brain protein secretion for the different tasks performed by the adult worker honeybees, in A. m. scutellata (Africanized) and A. m. ligustica (European), and how the deformed wing virus (DWV) could interfere with the performance of these tasks. The following analysis were carried out: protein tests (Bradford method) in the brain and in mandibular, hypopharyngeal, and thoracic and cephalic salivary glands, in Africanized and European honeybees at the ages of 0 (newborn), 5, 10, 15, 20, 25 and 30 days; measurements of the acini area of cephalic salivary and hypopharyngeal glands in those honeybees; evaluation of the development of tasks performed by honeybees and reversion of the laying workers of Africanized honeybees; test to detect DWV using real-time PCR in Africanized honeybees and in the brain and in mandibular, hypopharyngeal, and thoracic and cephalic salivary glands of European honeybees at the ages of 5 and 30 days; and morphological evaluation of the damages caused by the DWV acute infection in the brain and in the studied glands. Africanized and European honeybees showed statistically significant protein contents (p>0.05) for all the structures and ages studied. The acini areas of cephalic salivary and hypopharyngeal glands showed modifications according to the development of those glands at the different studied ages. It was observed that the swarms of bees with the same age are capable to perform different tasks needed to the survival of their colony, being the principal task, performed at the different studied ages, indicated by the significant protein contents found (p>0.05). The European honeybees at the same age showed higher acini development in the cephalic salivary gland than in the hypopharyngeal one at the initial studied ages, differing from the acini area in the same glands of honeybees grown in a regular colony. The worker honeybees can control the laying workers of the colony. Africanized and European honeybees showed positive results for DWV, which was also observed in thoracic salivary and mandibular glands in five-day-old honeybees. It was observed that the acute DWV infection causes morphological modifications in the honeybees glands, which show plasticity in the performance of tasks, not being them restricted to a particular age. Moreover, the DWV infection is not limiting for Africanized honeybees, but it is for the European ones.

A formação, recrutamento e manutenção de trilhas em formigas cortadeiras do gênero Atta é controlada quimicamente e envolve a participação de diferentes castas. Todavia, são escassos os estudos sobre a dinâmica das castas sob diferentes fontes de estímulos para a colônia, e como isso interfere na deposição de trilhas químicas. O presente trabalho visou compreender a influência de diferentes fontes de estímulos no padrão químico de deposição das trilhas, bem como no comportamento de recrutamento, forrageamento e defesa das operárias em Atta sexdens rubropilosa (Hymenoptera: Formicidae). Os resultados indicaram que houve variação do perfil etológico e alocação de tarefas desempenhadas pelos indivíduos presentes na colônia, de acordo com a fonte de estímulo. Neste caso foram oferecidos uma fonte de estímulo atrativa (\"pétalas de rosas\") e outra de agressividade (\"rainha de outra colônia\"). Além disso, os perfis químicos observados nas trilhas variaram qualitativamente e quantitativamente de acordo com os estímulos oferecidos. Estes dados sugerem que as operárias de A. sexdens rubropilosa seriam capazes de manejar quimicamente seu feromônio de trilha para informar e alterar o comportamento de suas companheiras de ninho, de acordo com a fonte de estímulo em que foram expostas. / Formation, recruitment and maintenance of trail in Atta leaf-cutting ants are chemically controlled and involve participation of different castes. Nevertheless, studies on caste dynamic under different stimuli to the colony are scarce, and how it interferes in the chemical deposition of the trail. This investigation aimed to understand how different source of stimuli influence the chemical pattern of trail marking as well as the recruitment, foraging and defense behavior by workers in Atta sexdens rubropilosa (Hymenoptera: Formicidae). Results indicate variation in the ethological profile and task allocation performed by the colony individuals, according to the stimuli source. In this case, it was offered an attractive stimulus source (\"rose petals\") and an aggressive one (\"other colony queen\"). Moreover, the chemical profiles of the trail varied qualitatively and quantitatively in response to the stimuli they were exposed. These data suggest that A. sexdens rubropilosa workers would be able to chemically manipulate their trail pheromone with aim to inform and alter their nestmate behavior in response to the exposed stimuli source.

The presence of soldier caste is an important synapomorphy of group Isoptera. The adaptation of this caste to defense tasks is more than obvious and some of their morphological or even behavioral adaptations can be quite impressive. The polyethism in termites is relatively well known inbetween rather worker caste. If there are such a studies pointing at polyethism in soldiers, they are connected with soldier polymorphism. The morphological differences are of course important stimulus to role separation. The goal of this thesis was to examine the polyethism in the species of the termite with monomorphic soldiers - Prorhinotermes simplex. I did behavioral experiments with it in enclosed arenas, recorded on specific days. The data shows, that there are differences inbetween individuals and it would be benefical to invest further time to subsequent studies. The thesis bring out new point of view to defensive behaviour of termites and suggests, that even termite species without polymorphic species may have soldiers with different tasks. Besides I managed to map ontogeny of soldier behaviour in the first two weeks after moulting from presoldier instar. Key words: Isoptera, polyethism, soldiers, ontogeny, defensive behaviour Powered by TCPDF (www.tcpdf.org)

In this paper we study the dynamics of task division in threshold reinforcement models of social insect societies. Our work extends other models in order to include several factors that influence the behavior of real insect colonies. Main extensions of our model are variable demands for work, age-dependent thresholds and finite life span of the individuals. It is shown how these factors influence the degree of task specialization of the individuals in a colony. Moreover, we show that the introduction of a threshold-dependent competition process between the individuals during task selection leads to the occurrence of specialists and differentiation between individuals as an emergent phenomenon that depends on the colony size. This result can help to explain the proximate mechanisms that lead to specialization in large insect colonies. Our results have implications for the fields of multi-agent systems, robotics, and nature inspired scheduling where threshold response models are used for control and regulation tasks.

The daily patterns of task performance in honey bee colonies during behavioral development were studied to determine the role of circadian rhythmicity in age-related division of labor. Although it is well known that foragers exhibit robust circadian patterns of activity in both field and laboratory settings, we report that many in-hive tasks are not allocated according to a daily rhythm but rather are performed 24 h per day. Around-the-clock activity at the colony level is accomplished through the performance of some tasks by individual workers randomly with respect to time of day. Bees are initially arrhythmic with respect to task performance but develop diel rhythmicity, by increasing the occurrence of inactivity at night, prior to becoming foragers. There are genotypic differences for age at onset of rhythmicity and our results suggest that these differences are correlated with genotypic variation in rate of behavioral development: genotypes of bees that progressed through the age polyethism schedule faster also acquired behavioral rhythmicity at an earlier age. The ontogeny of circadian rhythmicity in honey bee workers ensures that essential in-hive behaviors are performed around the clock but also allows the circadian clock to be engaged before the onset of foraging.

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Made available in DSpace on 2015-03-26T13:30:28Z (GMT). No. of bitstreams: 1 texto completo.pdf: 221617 bytes, checksum: 8dea1fe4e748dc72a9e46876a76c3606 (MD5) Previous issue date: 2010-02-12 / Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Age polyethism is the change in activities carried out by members of a colony during its life. Older individuals have lower future value to the colony, so it would be better for the colony if they could perform more dangerous tasks outside the nest and not return to its interior. Thus, the risk of bringing pathogens into the colony is reduced, protecting internal individuals and thereby increasing the life expectancy of the colony. The first hypothesis of this study is that external ants are older than internal ones and therefore die earlier. A complementary hypothesis is that external workers are weaker, having been previously selected by the colony to carry out dangerous tasks, since the losses would be less prejudicial to the colony. To test these hypotheses, internal e external workers of the leaf-cutter ant Atta laevigata (Smith) (Hymenoptera: Formicidae) were collected from nests in the field (Viçosa, Minas Gerais State, Brazil) and also from laboratory colonies. Ants of the same size were placed individually in Petri dishes and supplied with water and honey solution 1:1. To test the second hypothesis, ants were inoculated with the fungus Beauveria bassiana (Bals.) Vuill to compare their survival to controls. In both the field and laboratory experiments, the external workers died before the gardeners, suggesting that they are older, supporting the first hypothesis, that this species use age-dependent polyethism. In the experiment with ants from the field, there was no difference in the survival curves of external ants, inoculated or not. There was a difference in the laboratory ants. The first experiment indicates that external workers are not previously weaker, but the second suggests they are. This could be the difference betweennatural conditions (where they have more contact with pathogens so more susceptible individuals may be eliminated) and laboratory conditions (less pathogens). This study is the first step to test the conveyor belt model of Schmid-Hempel. Additional studies will be important to understand the intrinsic and extrinsic mechanisms mediating progression from internal to external activities, during aging. / O polietismo etário é a mudança nas atividades exercidas pelos membros de uma colônia ao longo da sua vida. Os indivíduos mais velhos teriam menor valor futuro para a colônia, seria então melhor se realizassem tarefas fora do ninho e não retornassem ao interior do mesmo. Isso diminuiria o risco de trazerem patógenos para dentro da colônia, o que consequentemente, aumentaria a expectativa de vida da colônia. A primeira hipótese desse trabalho é que as operárias de fora do ninho de formigas cortadeiras morrem antes das de dentro sugerindo que sejam mais velhas. Uma hipótese alternativa é que as formigas que forrageiam são operárias mais fracas, previamente escolhidas pela colônia, para realizarem tarefas mais perigosas, já que as perdas das mesmas não acarretariam tantos prejuízos. Para testá-las, operárias de dentro e fora do ninho da formiga cortadeira Atta laevigata (Smith) (Hymenoptera: Formicidae) foram coletadas de ninhos no campo (Viçosa, Minas Gerais, Brasil) e também de colônias provenientes de laboratório. Formigas de mesmo tamanho foram individualizadas em placas de Petri e supridas com água e solução de mel 1:1. Para testar a segunda hipótese, formigas foram inoculadas com o fungo Beauveria bassiana (Bals.) Vuill., com objetivo de comparar a sobrevivência dessas com formigas controle. As operárias de fora morreram antes das de dentro tanto no experimento de campo quanto no de laboratório. Isto sugere que sejam mais velhas, apoiando a primeira hipótese, que essa espécie utilize o polietismo dependente da idade. No experimento com formigas do campo, não houve diferença nas curvas de sobrevivência das de fora do ninho, inoculadas ou não; mas com as formigas de laboratório houve. O primeiro experimento indica que as formigas externas não são previamente mais fracas,mas o segundo indica que sim. Isso pode ter ocorrido pela diferença entre as condições naturais (onde têm mais contato com patógenos e indivíduos mais suscetíveis seriam eliminados) e as condições de laboratório (menos patógenos). Esse estudo foi o primeiro passo para se testar o modelo esteira de Schmid-Hempel. Estudos adicionais serão importantes para entender os mecanismos, extrínsecos e intrínsecos, mediadores das mudanças nas atividades internas ao ninho para atividades externas, com a passagem da idade.