The effect of water on the ground nesting habits of the giant tropical ant, Paraponera clavata
Abstract The large predatory ant, Paraponera clavata, exerts measurable top-down effects in wet and moist Neotropical forests, and therefore its distribution has potential ecological implications. To determine how water affects the presence of this important predator, the ground nesting ecology of P. clavata was examined with respect to various habitat characteristics. Four hectares of disturbed Costa Rican lowland rain forest were surveyed for ant colonies to determine nest distribution patterns in wet and dry habitat; significantly more colonies were found in dry habitat. Seventeen of 19 nests built on slopes of > 5° inclination were positioned on the downward side of the tree, possibly using the trunk as a shield against runoff during rain showers. Moisture and pH inside nests were significantly different from adjacent soil. These results suggest that water influences the ground nesting habits of P. clavata, thus ecological differences between comparatively wet and dry portions of tropical forests may arise from the relative abundance of this ant species.
Nest distribution and food preferences of Ectatomma ruidum (Hymenoptera: Formicidae) in shaded and open cattle pastures of Colombia.
Ectatomma ruidum is a common ground-dwelling ant species in the Neotropics which has been reported as a potential biocontrol agent in maize and coffee-cocoa agroecosystems in Mexico and Nicaragua. Its spatial distribution and food preferences were evaluated between February and May 2007, both in shaded (with tree cover) and sunny (open) cattle pastures in the Pescador and El Palmar regions of southwestern Colombia. Two sunny and two shaded cattle pasture plots were selected at each region. Twenty consecutive, equilateral 25 m parcels were established at each plot. Nest locations were found by following trails from 20 equidistant tuna baits per parcel. The procedure was repeated during the wet and dry seasons with a total of 16 plot records. For determining food preferences, a paper disk providing five live ticks, five honey droplets and five Passiflora ligularis seeds was placed 30 cm away from the nest entrance, at one nest for each of 15 parcels per plot. Nest distribution was aggregated in shaded pastures, with an average nest density of 568 nests/ha, whereas it was mainly random in sunny pastures, with an average nest density of 1945 nests/ha. Whatever the season, E. ruidum nested preferentially in open places in both regions, apparently avoiding soil surfaces under the tree canopy cover in shaded pastures. This could explain the aggregated pattern recorded in these pastures despite some intraspecific competition. Foragers demonstrated a high capacity as seed dispersers, the myrmecochoric P. ligularis seeds representing 74.7% of the total weight of all food items removed. Comparatively, they were significantly less attracted by honey and ticks which were retrieved in similar quantities (14.3% and 11.0% of the total weight removed, respectively). In the course of this study, individual workers were observed carrying in their mandibles wild, natural ticks, captured in the field. This is the first report of ants naturally preying on ticks in Colombia. Our data confirm the status ofE. ruidum as an important natural biocontrol agent which could be properly managed for ecological services in Neotropical agroecosystems.
Influence of Altitude and Temperature upon Rate of Oxygen Consumption of Tribolium Confusum Duval and Camponotus Pennsylvanicus Modoc Wheeler
LESLIE, P. H., and RANSON, R. M. 1940. The mortality, fertility and rate of natural increase of the vole (Microtus agrestis) as observed in the laboratory. Jour. Anim. Ecology, 9:27-52. LOTKA, A. J. 1925. Elements of physical biology. Baltimore: Williams & Wilkins Co. MACARTHUR, J. W., and BAILLIE, W. H. T. 1929a. Metabolic activity and duration of life. I. Influence of temperature on longevity in Daphnia magna. Jour. Exper. Zo6l., 53:221-42. --. 1929b. Metabolic activity and duration of life. II. Metabolic rates and their relation to longevity in Daphnia magna. Ibid., pp. 243-68.