Showing papers on "Ant colony published in 2001"

Individual versus social complexity, with particular reference to ant colonies

Abstract: Insect societies – colonies of ants, bees, wasps and termites – vary enormously in their social complexity. Social complexity is a broadly used term that encompasses many individual and colony-level traits and characteristics such as colony size, polymorphism and foraging strategy. A number of earlier studies have considered the relationships among various correlates of social complexity in insect societies; in this review, we build upon those studies by proposing additional correlates and show how all correlates can be integrated in a common explanatory framework. The various correlates are divided among four broad categories (sections). Under ‘polyphenism’ we consider the differences among individuals, in particular focusing upon ‘caste’ and specialization of individuals. This is followed by a section on ‘totipotency’ in which we consider the autonomy and subjugation of individuals. Under this heading we consider various aspects such as intracolony conflict, worker reproductive potential and physiological or morphological restrictions which limit individuals’ capacities to perform a range of tasks or functions. A section entitled ‘organization of work’ considers a variety of aspects, e.g. the ability to tackle group, team or partitioned tasks, foraging strategies and colony reliability and efficiency. A final section,‘communication and functional integration’, considers how individual activity is coordinated to produce an integrated and adaptive colony. Within each section we use illustrative examples drawn from the social insect literature (mostly from ants, for which there is the best data) to illustrate concepts or trends and make a number of predictions concerning how a particular trait is expected to correlate with other aspects of social complexity. Within each section we also expand the scope of the arguments to consider these relationships in a much broader sense of'sociality’ by drawing parallels with other ‘social’ entities such as multicellular individuals, which can be understood as ‘societies’ of cells. The aim is to draw out any parallels and common causal relationships among the correlates. Two themes run through the study. The first is the role of colony size as an important factor affecting social complexity. The second is the complexity of individual workers in relation to the complexity of the colony. Consequently, this is an ideal opportunity to test a previously proposed hypothesis that ‘individuals of highly social ant species are less complex than individuals from simple ant species’ in light of numerous social correlates. Our findings support this hypothesis. In summary, we conclude that, in general, complex societies are characterized by large colony size, worker polymorphism, strong behavioural specialization and loss of totipotency in its workers, low individual complexity, decentralized colony control and high system redundancy, low individual competence, a high degree of worker cooperation when tackling tasks, group foraging strategies, high tempo, multi-chambered tailor-made nests, high functional integration, relatively greater use of cues and modulatory signals to coordinate individuals and heterogeneous patterns of worker-worker interaction. Key words: Ants, insect societies, individual complexity, social complexity, polyphenism, totitpotency, work organization, functional integration, sociality.

Colony dispersal and the evolution of queen morphology in social Hymenoptera.

Abstract: ▪ Abstract Social Hymenoptera show two contrasting strategies of colony reproduction. A reproductive female can raise the first generation of brood alone (independent foundation), or a colony can divide into autonomous parts in which the reproductive female is helped by sterile relatives (fission, budding, swarming). In independent-founding ants, queens can histolize their flight muscles after dispersal; in many species, large flight muscles and metabolic reserves reduce or eliminate the need for risky foraging trips during the vulnerable solitary stage. Colony division is a derived strategy, and we review the selective pressures leading to its occurrence in the different social taxa. In various ants, fission coexists with independent foundation, and alate queens are retained. However, in ants exhibiting obligate fission (e.g. all army ants and many Ponerinae), queens are permanently wingless (ergatoid), or the queen caste is missing altogether. When reproductive females are flightless, dispersal distance...

Enhancement of Hydroelectric Generation Scheduling Using Ant Colony System-Based Optimization Approaches

Abstract: In this paper, an ant colony system (ACS) based optimization approach is proposed for the enhancement of hydroelectric generation scheduling. To apply the method to solve this problem, the search space of multi-stage scheduling is first determined. Through a collection of cooperative agents called ants, the near-optimal solution to the scheduling problem can be effectively achieved. In the algorithm, the state transition rule, local pheromone-updating rule, and global pheromone-updating rule are all added to facilitate the computation. Because this method can operate the population of agents simultaneously, the process stagnation can be better prevented. The optimization capability can be thus significantly enhanced. The proposed approach has been tested on Taiwan Power System (Taipower) through the utility data. Test results demonstrated the feasibility and effectiveness of the method for the application considered.

Automatically tracking and analyzing the behavior of live insect colonies

Abstract: We introduce the study of {\it live} social insect colonies as a relevant and exciting domain for the development and application of multi-agent systems modeling tools. Social insects provide a rich source of {\it traceable} social behavior for testing multi-agent tracking, prediction and modeling algorithms. An additional benefit of this research is the potential for contributions to experimental biology --- the principled techniques developed for analyzing artificial multi-agent systems can be applied to advance the state of knowledge of insect behavior. We contribute a novel machine vision system that addresses the challenge of tracking hundreds of small animals simultaneously. Fast color-based tracking is combined with movement-based tracking to locate ants in a real-time video stream. We also introduce new methods for analyzing the spatial activity of ant colonies. The system was validated in experiments with laboratory colonies of {\it Camponotus festinatus} and several example analyses of the colonies' spatial behavior are provided.

An ant colony based system for data mining: applications to medical data

Abstract: This work describes an algorithm for rule discovery in databases called AntMiner The objective of the algorithm is the extraction of classification rules to be applied to unseen data as a decision aid The algorithm used to discover such rules is inspired in the behavior of a real ant colony, as well as some concepts of information theory and data mining AntMiner was applied to medical databases to obtain classification rules

Optimisation techniques for electrical power systems. II. Heuristic optimisation methods

Abstract: For pt. I see ibid., vol.14, no.5, p.245-54 (2000). An introduction to mathematical programming based methods was given in the first tutorial of this three-part series. This second part covers major modern heuristic optimisation techniques and their integration and comparison with other methods. This paper discusses evolutionary algorithms; simulated annealing; tabu search; ant colony search; neural networks; and fuzzy programming.

Ant colony control for autonomous decentralized shop floor routing

Abstract: We introduce a new approach to autonomous decentralized shop floor routing. Our system, which we call Ant Colony Control (AC/sup 2/), applies the analogy of a colony of ants foraging for food to the problem of dynamic shop floor routing. In this system, artificial ants use only indirect communication to make all shop routing decisions by altering and reacting to their dynamically changing common environment through the use of simulated pheromone trails. For simple factory layouts, we show that the emergent behavior of the colony is comparable to using the optimal routing strategy. Furthermore, as the complexity of the factory layout is increased, we show that the adaptive behavior of AC/sup 2/ evolves local decision making policies that lead to near-optimal solutions from the standpoint of global performance.

A novel method for building regression tree models for QSAR based on artificial ant colony systems.

Abstract: Among the multitude of learning algorithms that can be employed for deriving quantitative structure-activity relationships, regression trees have the advantage of being able to handle large data sets, dynamically perform the key feature selection, and yield readily interpretable models. A conventional method of building a regression tree model is recursive partitioning, a fast greedy algorithm that works well in many, but not all, cases. This work introduces a novel method of data partitioning based on artificial ants. This method is shown to perform better than recursive partitioning on three well-studied data sets.

The phenology of a Neotropical ant assemblage: evidence for continuous and overlapping reproduction

Abstract: Reproductive phenologies reflect the interaction between the mating system of a taxon and the local environment. Ant colonies reproduce and disperse via the flights of winged alates. Few data exist on the reproductive phenologies of ant assemblages. Here we analyze the reproductive phenologies of 81 common ant species from 23,182 individuals collected over 3 years on Barro Colorado Island, Panama (BCI). Species ranged from highly synchronous to continuous fliers, but showed a median flight duration of at least 8 of 13 lunar months. In two statistical analyses (variance ratio test and Spearman rank correlations), 84% (16 of 19) of ant genera had species trending toward positively associated phenologies, more than expected by chance (P<0.00036 by a binomial test). Thus, there was little evidence for the hypothesis that competition for limiting resources staggers congeneric flights and ultimately promotes reproductive isolation. On the contrary, the timing of reproduction, and its synchrony, tended to be conserved within genera and subfamilies. These results closely match phenological studies of plant assemblages. The continuous reproduction and small colony size of many species in this study suggest that the female calling syndrome, a poorly documented mating system in ants, may be common on BCI.

Ant-nest distribution in a remnant of tropical rainforest in southeastern Brazil

Abstract: Ant communities are generally extremely interactive, and competition between ant species seems to be widespread. This characteristic of ant communities tends to produce a uniform pattern of nest distribution. In this study, we aimed to test the nest distribution pattern, putting forward hypotheses to explain the pattern. Nest mapping was carried out by delimiting ten one-square-meter quadrats, randomly located in a remnant of tropical rainforest in Vicosa, Brazil. In each quadrat, the nests were surveyed in the litter and surface soil up to 3 cm deep. A total of 295 nests from 41 ant species were collected in the ten quadrats. The pattern of nest distribution in the whole forest was aggregated, while the species showed a random distribution. The pattern of nest distribution inside each quadrat was also aggregated. The presence of species, such as Brachymyrmex sp.1 and Hypoponera sp.4 , with high nest densities suggests the occurrence of nest budding. This may be the reason for the aggregated nest distribution. Another explanation for this apparent aggregation is species specialization in a patchily distributed habitat. The results suggest that competition is not an important process in the regulation of soil and litter ants distribution and, consequently, in the regulation of species richness in the studied area.

Nutrient availability and indirect (biotic) defence in a Malaysian ant-plant

Abstract: Tropical plants of different genera defend themselves via symbiotic ant colonies, which are housed and often nourished by their host plant. Many studies deal with the defensive effects of the ants, but none has linked the plants' investment in this type of defence to the size and defensive efficacy of the symbiotic ant colony. We show here that ant-food production by the obligate myrmecophyte, Macaranga triloba, is limited by nutrient supply. The colony size of the ants in untreated plants (which had not been affected by experiments in advance of colony collection and determination of food body production) was significantly correlated with the amount of food produced by their hosts, and the plants' level of leaf damage was significantly and negatively correlated with the number of inhabiting ant workers. Our study provides the first field data that show that nutrient availability can directly influence a myrmecophyte's investment in its ants. Further studies are needed to evaluate whether soil nutrient contents in general can be a factor that limits the ability of myrmecophytes to defend themselves indirectly by nourishing symbiotic ants.

An Experimental Study of the Simple Ant Colony Optimization Algorithm

Abstract: Ant Colony Optimization (ACO) is a recently proposed metaheuristic inspired by the foraging behavior of ant colonies. Although it has been experimentally shown to be highly effective on a number of static and dynamic discrete optimization problems, only limited knowledge is available to explain why the metaheuristic is so successful. In this paper we propose a simple framework that allows the investigation of some basic properties of ACO and we report about some experiments and what we learned from them. Key-Words: Ant Colony Optimization, Simple-ACO algorithm, shortest path problem

Ant defence system: A mechanism organizing individual responses into efficient collective behavior

Abstract: A colony of social insects is an excellent model for investigating the organization of responses of subunits (i.e. colony members) with limited skills into sophisticated collective behavior. The defence system of Lasius niger ant colonies is well organized in a context-dependent way. The proportion of fighting ants to fleeing ants changes gradually according to the importance of the area being defended, and was higher where ants tended honeydew-rich aphids and on trails for foraging with heavy traffic, than where ants were walking alone or on trails with light traffic. Although there were intrinsic differences in aggressiveness between individual ants, the differences in aggressive responses between defended areas was not due to the presence of highly aggressive or timid individuals in each area. Instead, it was due to a change in aggressiveness of individuals in response to external conditions. The cue that altered individual aggressiveness was the presence of surrounding nest-mates, rather than the presence of aphids. We concluded that the defence system of this ant species consists of three processes: (i) a recruiting system that allocates more workers to more valuable resources; (ii) individual ants following a simple decision rule to become more aggressive in response to increased numbers of nest-mates nearby (hence aggressive behavior reflecting the importance of each area to the colony); and (iii) variability in individual responses causing a gradual change in the proportion of fighting ants responding to a threat.

Reproductive allocation within a polygyne, polydomous colony of the ant Myrmica rubra

Abstract: Summary 1. Ant colonies commonly have multiple egg-laying queens (secondary polygyny). Polygyny is frequently associated with polydomy (single colonies occupy multiple nest sites) and restricted dispersal of females. The production dynamics and reproductive allocation patterns within a population comprising one polygyne, polydomous colony of the red ant Myrmica rubra were studied. 2. Queen number per nest increased with nest density and the number of adult workers increased with the number of resident queens and with nest density. This suggests that nest site limitation promotes polygyny and that workers accumulate in nest units incapable of budding. 3. Nest productivity increased with the number of adult workers and production per queen was independent of queen number. Productivity increased with nest density, suggesting local resource enhancement. This shows that productivity can be a linear function of queen numbers and that the limiting factor is not the egg-laying capacity of queens. 4. The total and per capita production of reproductives decreased towards the periphery of the colony, suggesting that the spatial location of nest units affects sexual production. Thus nests at the periphery of the colony invested more heavily in new workers. This is consistent with earlier observations in plants and could either represent investment in future budding or increased defence. 5. The colony produced only five new queens and 2071 males, hence the sex ratio was extremely male biased.

Cooperative Ant Colonies for Optimizing Resource Allocation in Transportation

Abstract: In this paper we propose an ACO approach, where two colonies of ants aim to optimize total costs in a transportation network. This main objective consists of two sub goals, namely fleet size minimization and minimization of the vehicle movement costs, which are conflicting for some regions of the solution space. Thus, our two ant colonies optimize one of these sub-goals each and communicate information concerning solution quality. Our results show the potential of the proposed method.

Effects of food rewards offered by ant–plant Macaranga on the colony size of ants

Abstract: Myrmecophytes (ant‐plants) have special hollow structures (domatia) in which obligate ant partners nest. As the ants live only on the plants and feed exclusively on plant food bodies, sap-sucking homopterans in the domatia, and/or the homopteran’s honeydew, they are suitable for the study of colony size regulation by food. We examined factors regulating ant colony size in four myrmecophytic Macaranga species, which have strictly species-specific association with Crematogaster symbiont ants. Intra- and interspecific comparison of the plants showed that the ant biomass per unit food biomass was constant irrespective of plant developmental stage and plant species, suggesting that the ant colony size is limited by food supply. The primary food offered by the plants to the ants was different among Macaranga species. Ants in Macaranga beccariana and Macaranga bancana relied on homopterans rather than food bodies, and appeared to regulate the homopteran biomass and, as a consequence, regulate the ants’ own biomass. In contrast, ants in Macaranga winkleri and Macaranga trachyphylla relied primarily on food bodies rather than homopterans, and the plants appeared to manipulate the ant colony size. Per capita plant investment in ants (ant dry weight plant dry weight ‐1 ) was different among the four Macaranga species. The homoptera-dependent M. beccariana and M. bancana harbored lower biomass of ants than the food-body dependent M. winkleri, suggesting that energy loss is involved in the homoptera-interposing symbiotic system which has one additional trophic level. The plants’ investment ratio to the ants generally decreased as plants grew. The evolution of the plant reward-offering system in ant‐plant‐homopteran symbioses is discussed with an emphasis on the role of homopterans.

Optimal structural design by ant colony optimization

Abstract: Ant colony optimization (ACO) is a relatively new heuristic combinatorial optimization algorithm in which the search process is a stochastic procedure that incorporates positive feedback of accumulated information. The positive feedback (;i.e., autocatalysis) facility is a feature of ACO which gives an emergent search procedure such that the (common) problem of algorithm termination at local optima may be avoided and search for a global optimum is possible. The ACO algorithm is motivated by analogy with natural phenomena, in particular, the ability of a colony of ants to ‘optimize’ their collective endeavours. In this paper the biological background for ACO is explained and its computational implementation is presented in a structural design context. The particular implementation of ACO makes use of a tabu search (TS) local improvement phase to give a computationally enhanced algorithm (ACOTS). In this paper ACOTS is applied to the optimal structural design, in terms of weight minimization, of a ...

Bivouac checking, a novel behavior distinguishing obligate from opportunistic species of army-ant-following birds

Abstract: As swarms of the army ant Eciton burchelli forage across forest floors of the lowland Neotropics, birds gather to eat arthropods flushed by the advancing ants. Past efforts to distinguish members of the obligate ant-following bird guild from the many species that forage opportunistically with army ants have been inadequate. Obligate ant-followers track the locations of multiple nomadic ant colonies in order to maintain a consistent food supply. Each morning, they visit the bivouac site of each colony they are monitoring to assess the ants' activity. Only species dependent upon foraging with army ants exhibit this specialized bivouac checking behavior. This paper proposes a new method for distinguishing between obligate and opportunistic ant-following birds by observing which species check bivouacs. Verificacion de Vivaques, un Comportamiento Nuevo que Distingue a Especies Obligatorias de Especies Oportunistas Rastreadores de Hormigas-Ejercito Resumen. Cuando enjambres de la hormiga ejercito Ecito...

Ant Algorithms Solve Difficult Optimization Problems

Abstract: The ant algorithms research field builds on the idea that the study of the behavior of ant colonies or other social insects is interesting for computer scientists, because it provides models of distributed organization that can be used as a source of inspiration for the design of optimization and distributed control algorithms. In this paper we overview this growing research field, giving particular attention to ant colony optimization, the currently most successful example of ant algorithms, as well as to some other promising directions such as ant algorithms inspired by labor division and brood sorting.

The accumulated experience ant colony for the travelling salesman problem

Abstract: Ant colony optimisation techniques are usually guided by pheromone and heuristic cost information when choosing the next element to add to a solution. However, while an individual element may be attractive, usually its long term consequences are neither known nor considered. For instance, a short link in a TSP may be incorporated into an ant's solution, yet, as a consequence of this link, the rest of the path may be longer than if another link was chosen. The Accumulated Experience Ant Colony uses the previous experiences of the colony to guide in the choice of elements. This is in addition to the normal pheromone and heuristic costs. The results indicate that on some problems this helps to find improved solutions to the travelling salesman problem.

Ant Colony Optimisation for Bin Packing and Cutting Stock Problems

Abstract: The bin packing and the cutting stock problems are two well-known NP-hard combinatorial optimisation problems. Only very small instances can be solved exactly, so for real-world problems we have to rely on heuristic solution methods. In recent years, researchers have started to apply evolutionary approaches to these problems, including genetic algorithms and evolutionary programming. In this dissertation, I try to solve the bin packing and the cutting stock problem using ant colony optimisation, a new class of meta-heuristics introduced by Dorigo in 1992. This meta-heuristic is inspired by the path-finding abilities of real ant colonies. It combines an artificial pheromone trail with simple heuristic information to stochastically build new solutions. I show that this approach gives good results, especially when combined with local search, and that it can outperform existing evolutionary approaches. A disadvantage of the method is that it is quite sensitive to the relative weighing of the heuristic information as opposed to the pheromone trail information.

Phe-Q: A Pheromone Based Q-Learning

Abstract: Biological systems have often provided inspiration for the design of artificial systems. On such example of a natural system that has inspired researchers is the ant colony. In this paper an algorithm for multi-agent reinforcement learning, a modified Q-learning, is proposed. The algorithm is inspired by the natural behaviour of ants, which deposit pheromones in the environment to communicate. The benefit besides simulating ant behaviour in a colony is to design complex multi-agent systems. Complex behaviour can emerge from relatively simple interacting agents. The proposed Q-learning update equation includes a belief factor. The belief factor reflects the confidence the agent has in the pheromone detected in its environment. Agents communicate implicitly to co-operate in learning to solve a path-planning problem. The results indicate that combining synthetic pheromone with standard Q-learning speeds up the learning process. It will be shown that the agents can be biased towards a preferred solution by adjusting the pheromone deposit and evaporation rates.