1. Two field experiments were conducted to test the hypothesis that the intensity of predation by a generalist predator on two species of prey changes with the developmental stage of the predator. The generalist predator studied was Zelus renardii Kolenati (Hemiptera: Reduviidae) and the prey were the lacewing larva, Chrysoperla carnea Stephens, and the cotton aphid, Aphis gossypii Glover. 2. Zelus renardii and lacewings feed on aphids, thereby acting as potential competitors. In addition, Z. renardii feeds on lacewings. Thus, Z. renardii is an intraguild predator of lacewings. 3. Zelus renardii exhibited changes in prey preferences across developmental stages. The older stages of Z. renardii exerted greater mortality on lacewings and fed on larger lacewing larvae than did the younger stages. 4. Lacewings suppressed aphid population growth strongly. In contrast, none of the stages of Z. renardii was an effective control agent of the cotton aphid. 5. The addition of Z. renardii frequently disrupted the effective control of aphids generated by lacewings. In one of the two replicates of the experiment, the disruption increased with the developmental stage of Z. renardii, paralleling the increase in lacewing mortality. 6. Although the developmental stage of Z. renardii can influence the prevalence of intraguild predation and the intensity of the disruption of the aphid biological control, these experiments have demonstrated that even the youngest instars of Z. renardii can cause substantial lacewing mortality and release aphid populations from regulation.
The foraging behavior, within-plant vertical distribution, and microhabitat selection of 2nd instars and adults of Zeius renardii Kolenati were studied in an organic cotton field. In total, 47 individuals (21 nymphs and 26 adults) were observed foraging freely in the field for a total of94 h. Both developmental stages of Z. renardii consumed a wide variety of arthropods including herbivores lmd predators, but predatory insects comprised a greater fraction of the prey of adults compllred with nymphs. Adult Z. renardii also fed on larger prey compared with nymphs. Z. renardii recognized most prey from a distance, and the majority of the prey were moving when they were attacked, suggesting that this predator reacts strongly to visual stimuli. Nymphs and adults also were observed feeding on extrafloral nectaries located on the bottom ofleaves and at the base of fmiting structures, Activity budgets of nymphs and adults were similar, implying no gross changes in their foraging strategies; however, nymphs spent most of their time in the lower plant strata; the adults, in contrast, foraged primmily in the upper canopy. Nymphs also spent more time on the undersurface of leaves and less time on the petioles and stems compared with the adults. These changes in within-plant vertical distribution and microhabitat selection may influence the prey encounter rates and therefore the diet composition of nymphal and adult Z. renardii.
RESUMENEl presente estudio se propone determinar los hábitats efectivos y potenciales dentro de un parche de bosque seco secundario de 4.26 ha y la existencia de conexión de ésta área con otra área natural (estudio de paisaje) que sirva de corredor a la fauna silvestre en la comunidad La Chipopa, Nandaime. Los tipos de hábitats se seleccionaron según criterios florísticos. Para el estudio de conectividad y fragmentación se realizó un análisis con imágenes de satélite para determinar las clases de cobertura de la zona y se utilizaron como firmas espectrales las clases de cobertura vegetal 2011 del Ministerio de Agropecuario y Forestal (MAGFOR), la herramienta V_LATE 1.1 y la herramienta corridor desinger. Se determinaron siete tipos de hábitat. El hábitat de mayor tamaño fue el Área de árboles con poca infección con lianas (AAPL) (3.05 ha) la cual representa el 72 % del área total. En registro bibliográfico se determinaron 271 especies en el paisaje, de éstas, 102 (38 %) no encontrarían hábitat dentro del área. Los hábitats efectivos se determinaron por medio de muestreos anteriores, la mayor cantidad de especies (11 o el 33%) se asocia con AAPL. Dentro de los hábitats potenciales se encuentran: AAPL (23 o el 17 %) y Área de árboles con mucha infección por lianas (AAML) (12 o el 9%), sin embargo se determinaron que 26 especies (19%) prefieren toda el área como hábitat potencial. ABSTRACTThis study aims to identify effective and potential habitats inside a secondary dry forest patch of 4.26 ha and the existence of connection between this area and another natural area (the study of landscape) to serve as a corridor for wildlife in the Chipopa community, Nandarola, Nandaime. The habitats types were selected based on the floristic criteria. For the study of connectivity and fragmentation analysis was performed with satellite images to determine the types of coverage area and were used as spectral signatures of vegetation classes 2011 the Ministry of Agriculture and Forestry (MAG) and it was used theV_LATE 1.1 tool and the corridordesigner tool. The habitat was the largest area of trees with low infection lianas (AAPL) (3.05 ha) which represents 72% of the total area. In the bibliographic record 271 species were identified in the landscape, of these, 102 (38%) did not find habitat within the area. The effective habitats were determined through previous sampling, the main number of species (11 or 33%) were associate with AAPL. Among the potential habitats are: AAPL (23 or 17%) and area of trees with many lianas infection (AAML) (12 or 9%), however it is determined that 26 species (19%) prefer whole area as potential habitat. The landscape structure analysis indicates that the area is divided into 17 classes of coverage, which, the areas of secondary forests cover 48% of the total while the areas of crop and pasture cover at 34%. Inside the landscape matrix the closed forest use is the most fragmented area cause the shorten distance that a wildlife species should go to RECURSOS NATURALES
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