ABSTRACT. We investigated aggregation patterns in three fruit fly species economically important in Brazil, namely Ceratitis capitata, Anastrepha fraterculus, and A. obliqua. The study was carried out in a buffer zone and two neighbourhoods by comparing two-time series associated with the management strategy of fruit flies (systems approach). The abundance of these three species significantly decreased over the years with a negative binomial regression model describing the relationship between abundance and time in the entire area, buffer zone, and their neighbourhoods. In addition, the negative binomial model was also well fitted to the frequency distribution data of fruit flies in all analyzed scenarios. Anastrepha obliqua showed the highest aggregation degree, considering both the entire area and time series. A. fraterculus exhibited the lowest aggregation level, and C. capitata showed an intermediate degree. The buffer zone exhibited the highest aggregation degree for all species, and neighbourhood 2 exhibited the lowest aggregation degree. The aggregation degree was higher in the time series impacted by the systems approach than the series in the first years of its implementation.

ABSTRACT Interspecific competitions are important mechanisms in structuring ecological communities, including agroecosystems, in which different species may share the same food resource. In melons, two major pests coexist in time and space, Liriomyza sativae Blanchard (Diptera: Agromyzidae) and Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). The former feeds on the leaf mesophyll, while the latter on the phloem sap. Therefore, the same niche exploitation can trigger interactive processes between both populations. The present research aimed to determine if there are positive or negative interactions between whiteflies and leafminers under field conditions. The experiment was conducted in four commercial melon fields in northeast Brazil in two planting seasons. Thirty random plants were weekly selected for detection of whitefly nymphs and leafminer larvae throughout the entire crop cycle. The data was organized and analyzed considering the species abundance of L. sativae (larvae) and B. tabaci (nymphs and adults) in the same plant. Thus, the coabundance of species was investigated by using regressions with Poisson errors. The results suggest different fractions of negative, positive and neutral (not significant relationships) coabundance between the two species. Among 34 significant interactions, 56% were negative, suggesting that more than half of significant interactions are due to interspecific competition with negative coabundance.

RESUMO: Investigou-se a interferência do tamanho das gaiolas de criação de adultos de Chrysoperla externa (Hagen) sobre o seu potencial reprodutivo e sua sobrevivência. O tamanho das gaiolas de criação afetou significativamente o potencial reprodutivo deste crisopídeo. Os resultados indicaram que em gaiolas menores (7,5cm de diâmetro) do que as habitualmente usadas para a criação de adultos desse predador (10cm de diâmetro) ocorreram maiores taxas de oviposição. A redução de espaço para a criação de inimigos naturais para atender aos programas de controle biológico em laboratório é muito importante.

ABSTRACT: This study investigated the influence of cage sizes on the survival and reproductive potential of Chrysoperla externa (Hagen). Size of breeding cages significantly affected the reproductive potential of C. externa . Our results indicated that in cages smaller (7.5cm of diameter) than those usually recommended for the rearing of this insect (10cm diameter), females showed higher rates of oviposition. Reduction of space for rearing natural enemies in the laboratory is very important for developing biological control programs.

O objetivo deste trabalho foi comparar aspectos biológicos e parâmetros da tabela de vida dos coccinelídeos Harmonia axyridis, Cycloneda sanguinea e Hippodamia convergens.Os insetos foram alimentados com ovos de Anagasta kuehniella e criados a 24,5±1ºC, à umidade relativa de 70±10%, com fotófase de 12 horas. Para completar o desenvolvimento, H. convergenslevou aproximadamente 1,6 dia a mais do que H. axyridis, e 2,4 dias a mais do que C. sanguinea.Nos estágios iniciais, H. axyridisapresentou a maior percentagem de sobrevivência (49,2%), em comparação aos outros coccinelídeos. Quanto à longevidade média de adultos, H. convergensfoi deficiente, em comparação às outras espécies. A média do período de pré oviposição foi mais longo em C. sanguínea; o tempo de oviposição mais longo ocorreu em H. axyridis; e o período de pós oviposição foi similar entre os coccinelídeos. Considerando se os parâmetros reprodutivos,axyridisapresentou a melhor performance em todos os aspectos. Quanto à tabela de vida, os valores de convergens foram mais altos, embora aproximados dos de H. axyridis.No entanto, a alta taxa líquida de reprodução de H. axyridis mostrou o potencial desta espécie para aumentar o tamanho populacional. As características biológicas de H. axyridisfavorecem a invasão e o estabelecimento dessa espécie exótica no Brasil, o que corrobora os resultados observados em outros países.

The objective of this work was to compare biological aspects and life table parameters of the coccinellids Harmonia axyridis, Cycloneda sanguineaand Hippodamia convergens. Insects were fed eggs of Anagasta kuehniella, and reared at 24.5±1ºC, 70±10% relative humidity, with a 12 hour photophase. Hippodamia convergenstook about 1.6 day to complete development, longer than H. axyridis, and 2.4 day longer than C. sanguinea.At immature stages, H. axyridisexhibited the highest survival percentage (49.2%), in comparison to the other coccinellids. For mean adult longevity, H. convergenswas deficient, in comparison with the other species. Mean period of pre oviposition was the longest in C. sanguinea; the longest oviposition time occurred for H. axyridis; and the post oviposition period was similar between the coccinellids. Considering the reproductive parameters, H. axyridisshowed the best performance in all aspects. For life table, the values of H. convergenswere higher than, although close, to those of H. axyridis. Nevertheless, the high net reproductive rate of H. axyridis showed this species potential to increase population size. The biological characteristics of the exotic H. axyridis favors its invasion and establishment in Brazil, corroborating results noticed in other countries.

Chrysomya albiceps (Diptera: Calliphoridae) é uma predadora facultativa sobre outras moscas-varejeiras, durante o terceiro instar larval. Nesse estudo, nos investigamos a taxa de predação de C. albiceps sobre larvas de primeiro, segundo e terceiro instar de C. megacephala e C. macellaria comparando a vulnerabilidade dos instares larvais frente à predadora. Para as presas de primeiro e segundo instar, C. albiceps apresentou maior taxa de predação sobre C. megacephala. Já sobre larvas de terceiro instar a predadora consumiu mais C. macellaria. O comportamento de C. albiceps sobre as duas espécies de presas sugere uma mudança na estratégia de forrageio da predadora e essa mudança pode ter influencia sobre a comunidade de dípteros necrófagos.

During its larval stage, Chrysomya albiceps (Diptera: Calliphoridae) is a facultative predator on other blowflies. In this study, we evaluated the predation by third instar larvae of C. albiceps on first, second and third instar larvae of Chrysomya megacephala and Cochliomyia macellaria in no-choice experiments in order to compare the vulnerability of larval instars to predation. With first and second instar prey the highest predation rate by C. albiceps was on C. megacephala. For third instar prey, the highest predation rate was on C. macellaria. With second instar prey, there was complete predation on C. megacephala within 90 min, whereas in C. macellaria only 55% of the larvae were eaten by 90 min. For third instar prey most predation on C. macellaria (80%) occurred within 90 min, whereas in C. megacephala only 35% of the larvae were eaten by 90 min. Chrysomya albiceps changes the predatory behavior on its preys depending on which instar and species it will consume.

Neste estudo a dinâmica populacional de M. domestica foi avaliada em duas temperaturas, 20ºe 30ºC. A dinâmica foi modelada utilizando um modelo de crescimento populacional dependente da densidade. As temperaturas investigadas no estudo não produziram mudança qualitativa em termos de comportamento dinâmico, ou seja, a dinâmica populacional de M. domestica foi caracterizada por um equilíbrio estável em ambas as temperaturas. Entretanto, o ponto de equilíbrio foi influenciado pelos resultados obtidos nas diferentes temperaturas. A diferença entre os autovalores obtidos nas duas temperaturas foi a provável causa da diferença entre os pontos de equilíbrio. As implicações destes resultados para a dinâmica populacional de M. domestica são discutidas.

In the present study, the population dynamics of M. domestica was evaluated at two different temperatures, 20 and 30ºC. The dynamics was modeled using a density-dependent model of population growth. The temperatures investigated in this study produced no qualitative change in terms of dynamic behaviour, i. e. the population dynamics of M. domestica was characterized by a stable equilibrium at both temperatures. However, the steady state was influenced by the results obtained at different temperatures. The difference between the eigenvalues obtained at the two temperatures was probably the cause of the difference between the distinct steady states. The implications of these results for the population dynamics of M. domestica are discussed.

In this study we investigated the larval dispersal associated with larval predation in experimental populations of Chrysomya albiceps and Cochliomyia macellaria. Frequency distribution of sampling units (G test) in the substrate was used to evaluate variation in larval dispersal. An experimental acrylic channel (1 x 0.1 x 0.2 m) covered with wood shavings was used to observe larval dispersal prior to pupation. The acrylic channel was graduated at 0.05 m intervals, each representing a sampling unit; hence, 20 sampling units were set up. A Petri dish containing third instar larvae of single and double species was deposited at one edge of the acrylic channel allowing larvae to disperse. The number of buried pupae (0, 1, 2, …n) present in each sampling unit was recorded. For double species, the number of recovered larvae of C. albiceps was similar to the number initially released on the dish Petri. On the other hand, the number of recovered larvae of C. macellaria was significantly smaller than the initially released number. The results show that C. albiceps attacks C. macellaria larvae during the larval dispersal process. The larval distribution of C. albiceps did not differ significantly from C. macellaria in double species, but it differed significantly in single species. The larval aggregation level of C. macellaria decreased when C. albiceps was present and the larval aggregation level of C. albiceps increased when C. macellaria was present. The implications of such findings for the population dynamics of these species are discussed.

In this study we investigated predation rates on third instar larvae of Chrysomya putoria and C. megacephala by third instar larvae of C. albiceps in a two-choice situation. The highest predation rate occurred on C. putoria larvae and this result is compared to previous experiments, in which C. macellaria larvae were present. Our results suggest that, when C. macellaria is absent C. albiceps larvae attack more C. putoria than C. megacephala larvae. Prey choice decisions and its implications for introduced and native blowflies are discussed.

The sensitivity of parameters that govern the stability of population size in Chrysomya albiceps and describe its spatial dynamics was evaluated in this study. The dynamics was modeled using a density-dependent model of population growth. Our simulations show that variation in fecundity and mainly in survival has marked effect on the dynamics and indicates the possibility of transitions from one-point equilibrium to bounded oscillations. C. albiceps exhibits a two-point limit cycle, but the introduction of diffusive dispersal induces an evident qualitative shift from two-point limit cycle to a one fixed-point dynamics. Population dynamics of C. albiceps is here compared to dynamics of Cochliomyia macellaria, C. megacephala and C. putoria.