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Most animals move intermittently, pausing or slowing down for short moments and short moves, and darting away towards a new location where to hover again. This pattern occurs at a range of spatial and temporal scales (thence, resembling 'scale-free'), from the quick inspection of local areas to the sum of all movements performed from birth to death. While this pattern has been extensively described, its proximate drivers remain open to debate. A current hypothesis states that underlying proximate generative mechanisms of intermittent movement of animals are linked to external stimuli, e.g., interactions with the abiotic environment, resources, and other individuals. Here we investigated a prediction from this hypothesis, using termites as a biological model. We verified whether the social background in which a termite is inserted will modify the parameters of its intermittent scale-free spatial displacement. This relates to the hypothesis because it inspects how do external stimuli coming from intraspecifics can affect this type of movement. We tracked the trajectories of a focal termite confined along its nestmates in experimental clueless arenas, every 0.5 s along about six hours. Arenas varied in group size and comprised 22 distinct caste compositions, yielding 75 trackings (> 400 h) and more than two million Cartesian coordinates. Most of these trajectories (96% or 72/75) were classified as intermittent scale free (Lévy-like), indicating prevalence of this type of movement over non-Lévy-like ones (P=1.62×10-15). Moreover, intermittent scale-free movements performed by the focal termite (i) did arise outside the foraging-searching framework, and (ii) were modified by the social context while remaining within the limits of Lévy-walk realms. That is, some limits seem to exist along with the necessary plasticity to provide room for natural selection. Moreover, by arising outside the foraging framework, Lévy-like movements are shown to have broader relevance. Studies on processes that depend on social context and movement (e.g., collective behaviour, the spread of diseases) may, hence, profit from such concepts.

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Metalliferous soils can selectively shape plant species' physiology towards tolerance of high metal concentrations that are usually toxic to organisms. Some adapted plant species tolerate and accumulate metal in their tissues. These metals can serve as an elemental defence but can also decrease growth. Our investigation explored the capacity of natural metal accumulation in a tropical tree species, Eremanthus erythropappus (Asteraceae) and the effects of such bioaccumulation on plant responses to herbivory. Seedlings of E. erythropappus were grown in a glasshouse on soils that represented a metal concentration gradient (Al, Cu, Fe, Mn and Zn), and then the exposed plants were fed to the herbivores in a natural habitat. The effect of herbivory on plant growth was significantly mediated by foliar metal ion concentrations. The results suggest that herbivory effects on these plants change from negative to positive depending on soil metal concentration. Hence, these results provide quantitative evidence for a previously unsuspected interaction between herbivory and metal bioaccumulation on plant growth.

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As the number or density of interacting individuals in a social group increases, a transition can develop from uncorrelated and disordered behavior of the individuals to a collective coherent pattern. We expand this observation by exploring the fine details of termite movement patterns to demonstrate that the value of the scaling exponent µ of a power law describing the Lévy walk of an individual is modified collectively as the density of animals in the group changes. This effect is absent when termites interact with inert obstacles. We also show that the network of encounters and interactions among specific individuals is selective, resembling a preferential attachment mechanism that is important for social networking. Our data strongly suggest that preferential attachments, a phenomenon not reported previously, and favorite interactions with a limited number of acquaintances are responsible for the generation of Lévy movement patterns in these social insects.

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Structural and functional traits of organisms are known to be related to the size of individuals and to the size of their colonies when they belong to one. Among such traits, propensity to inquilinism in termites is known to relate positively to colony size. Larger termitaria hold larger diversity of facultative inquilines than smaller nests, whereas obligate inquilines seem unable to settle in nests smaller than a threshold volume. Respective underlying mechanisms, however, remain hypothetical. Here we test one of such hypotheses, namely, that nest defence correlates negatively to nest volume in Constrictotermes cyphergaster termites (Termitidae: Nasutitermitinae). As a surrogate to defence, we used 'patrolling rate', i.e., the number of termite individuals attending per unit time an experimentally damaged spot on the outer wall of their termitaria. We found that patrolling rate decayed allometrically with increasing nest size. Conspicuously higher patrolling rates occurred in smaller nests, while conspicuously lower rates occurred in larger nests presenting volumes in the vicinity of the threshold value for the establishment of inquilinism. This could be proven adaptive for the host and guest. At younger nest age, host colonies are smaller and presumably more vulnerable and unstable. Enhanced defence rates may, hence, prevent eventual risks to hosts from inquilinism at the same time that it prevents inquilines to settle in a still unstable nest. Conversely, when colonies grow and maturate enough to stand threats, they would invest in priorities other than active defence, opening an opportunity for inquilines to settle in nests which are more suitable or less risky. Under this two-fold process, cohabitation between host and inquiline could readily stabilize.

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Alarm signalling is of paramount importance to communication in all social insects. In termites, vibroacoustic and chemical alarm signalling are bound to operate synergistically but have never been studied simultaneously in a single species. Here, we inspected the functional significance of both communication channels in Constrictotermes cyphergaster (Termitidae: Nasutitermitinae), confirming the hypothesis that these are not exclusive, but rather complementary processes. In natural situations, the alarm predominantly attracts soldiers, which actively search for the source of a disturbance. Laboratory testing revealed that the frontal gland of soldiers produces a rich mixture of terpenoid compounds including an alarm pheromone. Extensive testing led to identification of the alarm pheromone being composed of abundant monoterpene hydrocarbons (1S)-α-pinene and myrcene, along with a minor component, (E)-ß-ocimene. The vibratory alarm signalling consists of vibratory movements evidenced as bursts; a series of beats produced predominantly by soldiers. Exposing termite groups to various mixtures containing the alarm pheromone (crushed soldier heads, frontal gland extracts, mixture of all monoterpenes, and the alarm pheromone mixture made of standards) resulted in significantly higher activity in the tested groups and also increased intensity of the vibratory alarm communication, with the responses clearly dose-dependent. Lower doses of the pheromone provoked higher numbers of vibratory signals compared to higher doses. Higher doses induced long-term running of all termites without stops necessary to perform vibratory behaviour. Surprisingly, even crushed worker heads led to low (but significant) increases in the alarm responses, suggesting that other unknown compound in the worker's head is perceived and answered by termites. Our results demonstrate the existence of different alarm levels in termites, with lower levels being communicated through vibratory signals, and higher levels causing general alarm or retreat being communicated through the alarm pheromone.

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Animal movements have been related to optimal foraging strategies where self-similar trajectories are central. Most of the experimental studies done so far have focused mainly on fitting statistical models to data in order to test for movement patterns described by power-laws. Here we show by analyzing over half a million movement displacements that isolated termite workers actually exhibit a range of very interesting dynamical properties--including Lévy flights--in their exploratory behaviour. Going beyond the current trend of statistical model fitting alone, our study analyses anomalous diffusion and structure functions to estimate values of the scaling exponents describing displacement statistics. We evince the fractal nature of the movement patterns and show how the scaling exponents describing termite space exploration intriguingly comply with mathematical relations found in the physics of transport phenomena. By doing this, we rescue a rich variety of physical and biological phenomenology that can be potentially important and meaningful for the study of complex animal behavior and, in particular, for the study of how patterns of exploratory behaviour of individual social insects may impact not only their feeding demands but also nestmate encounter patterns and, hence, their dynamics at the social scale.

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How do termite inquilines manage to cohabit termitaria along with the termite builder species? With this in mind, we analysed one of the several strategies that inquilines could use to circumvent conflicts with their hosts, namely, the use of distinct diets. We inspected overlapping patterns for the diets of several cohabiting Neotropical termite species, as inferred from carbon and nitrogen isotopic signatures for termite individuals. Cohabitant communities from distinct termitaria presented overlapping diet spaces, indicating that they exploited similar diets at the regional scale. When such communities were split into their components, full diet segregation could be observed between builders and inquilines, at regional (environment-wide) and local (termitarium) scales. Additionally, diet segregation among inquilines themselves was also observed in the vast majority of inspected termitaria. Inquiline species distribution among termitaria was not random. Environmental-wide diet similarity, coupled with local diet segregation and deterministic inquiline distribution, could denounce interactions for feeding resources. However, inquilines and builders not sharing the same termitarium, and thus not subject to potential conflicts, still exhibited distinct diets. Moreover, the areas of the builder's diet space and that of its inquilines did not correlate negatively. Accordingly, the diet areas of builders which hosted inquilines were in average as large as the areas of builders hosting no inquilines. Such results indicate the possibility that dietary partitioning by these cohabiting termites was not majorly driven by current interactive constraints. Rather, it seems to be a result of traits previously fixed in the evolutionary past of cohabitants.

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The effects of increasing plant diversity on the population of the coffee leaf-miner Leucoptera coffeella (Guérin-Mèneville) were investigated in two organic coffee production systems. One system consisted of coffee intercropped with banana trees (shaded system) and the other one of coffee intercropped with pigeon pea (unshaded system). The increase in plant diversity on both systems was achieved via introduction of green manures such a perennial pea nut, sunn hemp and Brazilian lucerne. The population of L. coffeella, predation and parasitism of L. coffeella mines were biweekly evaluated during eight months. The increase in plant diversity on both systems did not affect the attack of L. coffeella on coffee leaves and the mine parasitism rate. However, there was a positive and significant relationship between increasing plant diversity and coffee leaf mine predation by wasps on unshaded coffee system and a negative relationship on shaded coffee system.

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The effects of increasing plant diversity on the population of the coffee leaf-miner Leucoptera coffeella (Guérin-Mèneville) were investigated in two organic coffee production systems. One system consisted of coffee intercropped with banana trees (shaded system) and the other one of coffee intercropped with pigeon pea (unshaded system). The increase in plant diversity on both systems was achieved via introduction of green manures such a perennial pea nut, sunn hemp and Brazilian lucerne. The population of L. coffeella, predation and parasitism of L. coffeella mines were biweekly evaluated during eight months. The increase in plant diversity on both systems did not affect the attack of L. coffeella on coffee leaves and the mine parasitism rate. However, there was a positive and significant relationship between increasing plant diversity and coffee leaf mine predation by wasps on unshaded coffee system and a negative relationship on shaded coffee system.

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This is the first published report concerning reproduction and survival using life table analyses of fertility and survival for Muscina stabulans maintained under laboratory conditions with artificial diets. The intrinsic rate of growth, reproduction rate and average generational time were obtained, suggesting a rapid population growth under these rearing conditions. These findings permitted the creation of time models of survival and oviposition, as well as a quantitative estimate of the adaptation capacity of this species.

Com o objetivo de apresentar um primeiro delineamento para a reprodução e sobrevivência da Muscina stabulans em condições de laboratório, foram desenvolvidas tabelas de vida em dieta artificial. A taxa intrínseca de crescimento natural, a taxa reprodutiva líquida e o tempo médio de uma geração foram estimados, além da análise do tempo de oviposição e da sobrevivência dos adultos dessa espécie. Os dados sugerem uma alta taxa de crescimento da população nas condições de criação. Esses resultados permitem a criação de modelos de sobrevivência e oviposição, bem como estimativas quantitativas da adaptabilidade dessa espécie.

RESUMO

This is the first published report concerning reproduction and survival using life table analyses of fertility and survival for Muscina stabulans maintained under laboratory conditions with artificial diets. The intrinsic rate of growth, reproduction rate and average generational time were obtained, suggesting a rapid population growth under these rearing conditions. These findings permitted the creation of time models of survival and oviposition, as well as a quantitative estimate of the adaptation capacity of this species.

Com o objetivo de apresentar um primeiro delineamento para a reprodução e sobrevivência da Muscina stabulans em condições de laboratório, foram desenvolvidas tabelas de vida em dieta artificial. A taxa intrínseca de crescimento natural, a taxa reprodutiva líquida e o tempo médio de uma geração foram estimados, além da análise do tempo de oviposição e da sobrevivência dos adultos dessa espécie. Os dados sugerem uma alta taxa de crescimento da população nas condições de criação. Esses resultados permitem a criação de modelos de sobrevivência e oviposição, bem como estimativas quantitativas da adaptabilidade dessa espécie.

RESUMO

This is the first published report concerning reproduction and survival using life table analyses of fertility and survival for Muscina stabulans maintained under laboratory conditions with artificial diets. The intrinsic rate of growth, reproduction rate and average generational time were obtained, suggesting a rapid population growth under these rearing conditions. These findings permitted the creation of time models of survival and oviposition, as well as a quantitative estimate of the adaptation capacity of this species.

Com o objetivo de apresentar um primeiro delineamento para a reprodução e sobrevivência da Muscina stabulans em condições de laboratório, foram desenvolvidas tabelas de vida em dieta artificial. A taxa intrínseca de crescimento natural, a taxa reprodutiva líquida e o tempo médio de uma geração foram estimados, além da análise do tempo de oviposição e da sobrevivência dos adultos dessa espécie. Os dados sugerem uma alta taxa de crescimento da população nas condições de criação. Esses resultados permitem a criação de modelos de sobrevivência e oviposição, bem como estimativas quantitativas da adaptabilidade dessa espécie.

RESUMO

Interactions among individuals in social groups lead to the emergence of collective behaviour at large scales by means of multiplicative non-linear effects. Group foraging, nest building and task allocation are just some well-known examples present in social insects. However the precise mechanisms at the individual level that trigger and amplify social phenomena are not fully understood. Here we show evidence of complex dynamics in groups of the termite, Cornitermes cumulans (Kollar) (Isoptera: Termitidae), of different sizes and qualitatively compare the behaviour observed with that exhibited by agent-based computer models. It is then concluded that certain aspects of social behaviour in insects have a universal basis common to interconnected systems and that this may be useful for understanding the temporal dynamics of systems displaying social behaviour in general.

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Foi testada a eficiência de duas profundidades de aplicação de cupinicidas líquidos para o controle de cupins de montículo Cornitermes sp. (Isoptera: Termitidae) em pastagens na região Sul de Minas Gerais. Estes aplicadores diferiam basicamente quanto à profundidade e distribuição da calda cupinicida dentro do ninho, sendo um aplicador de tubo curto e outro de tubo longo e perfurado. Os resultados mostram que, o aplicador e tubo longo e perfurado apresenta maior eficiência de controle de cupins de montículo em pastagem e que a profundidade e distribuição de aplicação da calda cupinicida interfere na taxa de mortalidade das colônias. O uso de um aplicador com tubo longo, pode ser uma estratégia adequada para o efetivo controle de cupins de montículo, quando se utilizam inseticidas em formulação líquida.

The efficacy of two depths was tested for the control of mound termites, Cornitermes sp. (Isoptera: Termitidae) using liquid a formulation of imidacloprid. Both devices were funnels constructed so as to differ only in the depth and distribution of the liquid within the termite nest. One of the devices was a standard funnel, whereas the other presented a longer tube perforated along its extension and closed in the outer end. Termites in mounds treated with the long funnel died faster than termites treated with the short funnel. It seems that the depth and distribution of the insecticide within termite nest was crucial for the efficacy of the control. We therefore recommend that control methods of termite in mounds should favor the use of applying devices which distribute better the insecticide within the nest.