Effect of the Size of Workers of Atta sexdens rubropilosa on the Attack Behavior of Neodohrniphora spp. (Diptera: Phoridae)

摘要

We investigated whether the thickness of the food substrate modify the mean size of leaf-cutter ant (Atta sexdens rubropilosa) workers recruited to a food source and how different sizes of ant hosts affect the attack behavior of the phorids pxa.sitoids, Neodorhniphora spp. The ants used in the experiments were obtained from adult colonies maintained in the laboratory. Phorids were captured daily as they hovered over ant workers in the field. In the first experiment, artificial food of three differentthicknesses were offered to an ant colony, in different foraging arenas. The size of the workers recruited to each arena was recorded. In a second experiment, single ant workers or groups of workers, with sizes determined in the first experiment, were placed in an observation cube where a female phorid was subsequently released. In a third experiment, ants of two different size classes were mixed with smaller ants and placed in an observation arena into which a phorid female was released. In a fourth experiment, large ants were placed in two densities in the observation arena where a female phorid was rhen introduced. In the three tests with phorids (n= 15 in each test) the attack behavior of the parasitoid was observed. The duration of the inspectionflights and the numbers of attacking bouts and attacks were recorded. The thickness of the artificial food affected the mean size of recruited ants. The thinnest artificial food (0.5 mm) attracted ants with a mean size of 11 mg (confidence interval (CI)= 9.8 - 12.1 mg), which was significantly smaller than the ants attracted to the thickest substrate (3 mm), which weighed 21 mg (CI 18.1 - 23.9 mg). The size of the ants significantly modified the attack behavior of the phorid flies.