Mechanisms of carbohydrate‐fuelled ecological dominance in a tropical rainforest canopy‐foraging ant

1. Canopy‐foraging ants have carbohydrate‐rich diets and the stoichiometric excess of carbon may result in energetic allocation decisions that facilitate ecological dominance. 2. If dietary carbohydrates facilitate ecological dominance in canopy ants, then the mechanism for this relationship is unknown. 3. Four hypotheses were posit that may explain how a carbohydrate‐rich diet might facilitate ecological dominance in canopy ants: Aggressive Defense, Metabolic Fuel, Foraging Success, and Prey Acquisition. 4. To assess these hypotheses, experiments were conducted on the canopy‐foraging bullet ant, Paraponera clavata (Fabricius), an omnivorous species that demonstrates high variability in the relative contribution of carbohydrates to the diets of colonies. 5. No support was found for the Aggressive Defense, Metabolic Fuel and Prey Acquisition hypotheses. 6. The Foraging Success hypothesis was supported, as the proportion of nectar in the diet predicted the overall foraging success. 7. It was argued that there is no explicit advantage in the exploitation of nectar over other food resources, other than the fact that it is the most accessible food resource in the rainforest canopy.     

Off‐host aggregation in the non‐fed,female brown dog tick,Rhipicephalus sanguineus (Latreille), is induced by tick excreta and enhanced by low relative humidity

We report that Rhipicephalus sanguineus (Ixodida: Ixodidae) faeces and its main component, guanine, act as assembly pheromones in short‐range Petri plate bioassays. Arrestment activity in response to guanine was lower than that in response to natural excreta, indicating the presence of other active ingredients in natural excreta. The selective removal of appendages was used to establish the important roles played by the palps and the front pair of legs in the detection of the pheromone. Reaction to chemically pure guanine at varying concentrations occurred without a dose response; thus only the presence of guanine, not a critical amount, is required to induce assembly. Higher speed and intensity of clustering occurred at 33% relative humidity (RH). We conclude that female adults of R. sanguineus are more prone to assemble under dry conditions that match the arid microhabitats preferred by this species and that this tendency allows this tick to reside in human dwellings and dog kennels that maintain standards of comfort at 30–50% RH. Cleaning or removing tick excreta‐covered surfaces on which ticks aggregate from within and around human dwellings may prove useful as a means of interfering with the establishment of off‐host clusters of R. sanguineus.