Arthropod predators often use prey and conspecific cues to make foraging decisions. Calosoma wilcoxi (Leconte) is a voracious predatory beetle that specializes on lepidopteran larvae often found in the forest canopy, including the fall cankerworm. This study tested the hypothesis that C. wilcoxi uses olfactory cues to detect prey and conspecifics. A Y-tube olfactometer was used to test attractiveness to larvae, larval frass, conspecific cues, and volatiles from herbivore-damaged white oak leaves. C. wilcoxi did not preferentially choose the treatment in any of the experiments. There was no difference in mean time spent in the treatment or control arm for any of the cues assayed. The time to choose the treatment was significantly shorter in the female conspecific experiment only. I found no evidence that C. wilcoxi uses olfaction to locate prey; however, C. wilcoxi is attracted to conspecifics. C. wilcoxi may use conspecific cues to make informed foraging decisions.

In the Midwestern US, forested and other woody plant habitats are embedded in a matrix of agricultural and urban landcover that alters configurations of “natural” habitats and creates novel habitat types. Variation in the type and juxtaposition of landcover in the matrix between habitats can profoundly impact the spatial and temporal distributions of insects. Intense urban and agricultural development alters habitats, increases fragmentation, and may decouple trophic interactions if plants or animals cannot disperse to needed resources. Specialist insects represent a substantial proportion of global biodiversity and their fidelity to discrete microhabitats provides a powerful framework for investigating organismal responses to human land use. Specialist herbivores and parasitoids that depend on discrete plant habitats simplify assessment of how trophic interactions, local demographic traits, and dispersal processes affect responses to landcover heterogeneity. Herbivore responses to landcover change are highly idiosyncratic and not well characterized. Parasitoid wasps are predicted to be more prone than their herbivore hosts to local extinction in response to increased habitat fragmentation, but often respond differently to similar landcover contexts. Understanding and predicting idiosyncratic spatial population dynamics of simple host-parasitoid communities and other insect systems requires integration of metacommunity-level ecological paradigms with spatial analyses across multiple spatial scales. We sampled site occupancy and densities for two plant-herbivore-parasitoid systems from 250 sites across a 360 km2 urban/ agricultural landscape across three study years to ask whether and how human development decouples interactions between trophic levels. We first performed a single year analysis to investigate broad scale patterns. We compared patterns of site occupancy, host plant density, herbivory and parasitism rates of insects at two trophic levels with respect to landcover at multiple spatial scales. Geospatial analyses were used to identify landcover characters predictive of insect distributions. We found that herbivorous insect densities were decoupled from host tree densities in urban landcover types at several spatial scales. This effect was amplified for the third trophic level in one of the two insect systems: despite being abundant regionally, a parasitoid species was absent from all urban/ suburban landcover even where its herbivore host was common. Our results indicate that human land use patterns limit distributions of specialist insects. Dispersal constraints associated with urban built development are specifically implicated as a limiting factor. Our multi-year analysis of trophic interactions in urban versus agricultural landcover showed that important results from our single-year study are consistent over time and provided useful insights into the factors mediating spatial distributions of specialist insects in altered landscapes. While we observed that insect species responded to landcover at consistent local- and landscape-scale spatial extents, we observed that coarse grain landcover categories (i.e. urban versus agricultural) at low spatial resolution yielded the most consistent patterns of organismal response. Our results indicate that agricultural versus urban landcover contexts can mediate distinct spatial population structuring across linked trophic levels. This finding has important implications for conservation and pest management strategies in heterogeneous landscapes and is an important consideration when translating heuristics regarding metacommunity dynamics from one broad spatial context to another.

The ecology and evolution of a species is often considered only within the context of pairwise interactions even though a species' distribution and abundance may be determined by interactions with many species within and between trophic levels. Multiple herbivores often share the same host and may interact indirectly by altering the relationships between herbivores, their host plants and their parasitoids. However, the relationships between parasitoids and herbivore hosts have typically been studied in isolation of other herbivore species. I examined how the outcomes of species interactions change when multiple relationships are considered. Chapter 1 examined the potentially conflicting selection pressures Manduca sexta exerts on Nicotiana tabacum (tobacco), since M. sexta has pollinating adults but herbivorous larvae. I demonstrated that high nectar amino acids do not affect floral visitation, but increased oviposition of herbivores on leaves. Thus, the relative costs and benefits of nectar rewards may depend on the community of pollinators and their life histories. In the remaining chapters I examined how feeding on tobacco by the aphid Myzus persicae altered the interactions between a parasitoid (Cotesia congregata) and its hornworm host (M. sexta). Chapter 2 demonstrated that aphids reduced hornworm abundance and parasitism. Changes in hornworm abundance were not due to density-dependent changes in moth oviposition, but the proportion of caterpillars attacked by parasitoids was inversely density dependent with hornworm density. Chapter 3 examined whether changes in hornworm abundance and parasitism reflected aphid-induced changes in host plant quality or volatile emissions. Aphids increased hornworm mortality, did not affect parasitoid performance, and increased parasitoid search time. In combination with Chapter 2, results suggest that aphids can mediate parasitoid-caterpillar interactions through changes in host plants that reduce hornworm survival and alter parasitoid behavior. Chapter 4 addressed how the outcome of interactions that are altered by aphids changed with spatial scale, and found no effect spatial scale on hornworm abundance and parasitism. In this system, aphids alter parasitoid-caterpillar interactions through changes in plant quality that reduce hornworm performance and abundance, and in turn, influence parasitoid attack. This work demonstrates that the outcome of multispecies interactions may not be predictable from pairwise interactions. / Ph. D.

A agregação em insetos centra-se nas vantagens relativas ao forrageio e no aumento da defesa contra predadores. Além disso, agregações de ovos podem beneficiar-se pelo aumento nas taxas de eclosão larval. Neste trabalho, foram testadas as hipóteses de que agregações de Ascia monuste orseis (Godart, 1819) (Lepidoptera: Pieridae) uma espécie que se alimenta em agregações larvais em plantas da família Brassicaceae - conferem benefícios à performance larval e adulta, na assimilação de alimento pelas larvas, na viabilidade dos ovos e na proteção larval contra inimigos naturais. A possibilidade de um dado comportamento do grupo resultar em maior ataque por inimigos naturais também foi avaliada, bem como um padrão comportamental defensivo em resposta aos inimigos naturais. Para tanto, quatro tratamentos de diferentes tamanhos de agregações larvais foram formados (1, 7, 15 e 30 larvas) para avaliar a performance e a assimilação de alimento em laboratório. Em campo, três tratamentos foram formados (1, 10 e 50 larvas) para testar o efeito do tamanho do tamanho do grupo na predação e parasitismo. A performance do estágio de ovo foi examinada em posturas de tamanhos variados em casa de vegetação. Larvas gregárias desenvolveram-se mais rápido nos ínstares iniciais e tornaram-se fêmeas mais fecundas em comparação às solitárias; entretanto, larvas solitárias apresentaram maior tamanho do que as gregárias. A sobrevivência não diferiu entre os tratamentos em laboratório. Foi observado um menor consumo per capita de alimento por larvas gregárias, sem custos para a assimilação de alimento. A viabilidade dos ovos aumentou com o tamanho da agregação de ovos, comprovando o benefício da agregação larval na fase de ovo. A menor predação per capita em agregações larvais maiores conferiu uma maior proteção às larvas de A. monuste orseis contra predadores e parasitoides, através do efeito da diluição do ataque entre os indivíduos do grupo. O parasitoidismo foi mais expressivo em larvas de primeiros ínstares, enquanto que larvas mais tardias foram mais atacadas por predadores, independente do tamanho da agregação. Por fim, eventos comportamentais que envolvem movimentação da cabeça como exploração e alimentação foram mais perigosos para as larvas de A. monuste orseis em comparação ao repouso e deslocamento, semelhantemente a espécies de hábito solitário. Eventos comportamentais supostamente defensivos foram observados em todos os ínstares e tratamentos. As vantagens da agregação em A. monuste orseis mostraram-se especialmente importantes no estágio de ovo e primeiros ínstares, pela diminuição da mortalidade de ovos e vulnerabilidade larval aos inimigos naturais. Esses benefícios provavelmente sobrepõem-se aos custos, como a competição por interferência observada entre as larvas no final do desenvolvimento. Nossos resultados mostram que o malogro dos ovos e os efeitos dos inimigos naturais constituem fortes pressões seletivas na manutenção da agregação de ovos e larval em A. monuste orseis, a qual confere uma melhor performance do ponto de vista bi-trófico, bem como maior probabilidade de sobrevivência individual sob o ponto de vista tri-trófico. / In insects, the gregarious habit has been shown to improve foraging and defense against predation to both larval and adult stages. Egg clusters could also be beneficial through increased larval hatching. In this study, we tested the hypothesis that egg clusters and larval aggregations of the neotropical butterfly Ascia monuste orseis (Godart, 1819) (Pieridae) - a subspecies that uses Brassicaceae as hosts - lead to several benefits from both bi- and tri-trophic perspectives. Larval and adult performances, food assimilation by the larvae, egg viability, as well as protection against natural enemies were assessed from individuals reared either isolated or aggregated. The behavior of larval aggregations was also examined with respect to predation risk, as well as the corresponding larval defensive behaviors after enemy attack. Four treatments with different larval aggregation sizes were assigned (1, 7, 15 e 30 larvae) to assess larval performance and food utilization in the laboratory. In the field, three treatments were assigned (1, 10 e 50 larvae) to evaluate the effects of group size on predation and parasitoidism. Egg performance was examined through egg clusters of different sizes in a greenhouse. Gregarious larvae developed faster, especially in early instars, and became more fecund females than solitary larvae; however, the latter attained larger body size than the former. Under laboratory conditions, survival did not differ among treatments. Lower food ingestion per capita was observed in gregarious larvae, with no cost in food assimilation. The viability of eggs increased as egg aggregation size increased. The lower per capita predation in larger larval aggregations than smaller groups conferred higher protection to A. monuste orseis larvae against natural enemies, through the dilution effects among individuals of the group. Parasitoidism was more intense in small-sized larvae while late instars were more susceptible to predators, regardless of aggregation size. Similar to species with solitary habit, behavioral events which involved head movements as searching and feeding were more dangerous to A. monuste orseis larvae compared to resting and walking. Presumed defensive behaviors were observed in all instars and treatments. Thus, the benefits of aggregation in A. monuste orseis can be seen especially in the egg stage and in first instars, as it reduces egg mortality and larval vulnerability to natural enemies. These benefits probably overcome some costs, such as interference competition in the late instars. Taken together, the results show that egg failure and top-down effects constitute selective pressures in maintaining egg and larval aggregation in A. monuste orseis, by providing better performance from a bi-trophic perspective and increased probability of individual survival from a tri-trophic perspective when compared to solitary individuals.

A agregação em insetos centra-se nas vantagens relativas ao forrageio e no aumento da defesa contra predadores. Além disso, agregações de ovos podem beneficiar-se pelo aumento nas taxas de eclosão larval. Neste trabalho, foram testadas as hipóteses de que agregações de Ascia monuste orseis (Godart, 1819) (Lepidoptera: Pieridae) uma espécie que se alimenta em agregações larvais em plantas da família Brassicaceae - conferem benefícios à performance larval e adulta, na assimilação de alimento pelas larvas, na viabilidade dos ovos e na proteção larval contra inimigos naturais. A possibilidade de um dado comportamento do grupo resultar em maior ataque por inimigos naturais também foi avaliada, bem como um padrão comportamental defensivo em resposta aos inimigos naturais. Para tanto, quatro tratamentos de diferentes tamanhos de agregações larvais foram formados (1, 7, 15 e 30 larvas) para avaliar a performance e a assimilação de alimento em laboratório. Em campo, três tratamentos foram formados (1, 10 e 50 larvas) para testar o efeito do tamanho do tamanho do grupo na predação e parasitismo. A performance do estágio de ovo foi examinada em posturas de tamanhos variados em casa de vegetação. Larvas gregárias desenvolveram-se mais rápido nos ínstares iniciais e tornaram-se fêmeas mais fecundas em comparação às solitárias; entretanto, larvas solitárias apresentaram maior tamanho do que as gregárias. A sobrevivência não diferiu entre os tratamentos em laboratório. Foi observado um menor consumo per capita de alimento por larvas gregárias, sem custos para a assimilação de alimento. A viabilidade dos ovos aumentou com o tamanho da agregação de ovos, comprovando o benefício da agregação larval na fase de ovo. A menor predação per capita em agregações larvais maiores conferiu uma maior proteção às larvas de A. monuste orseis contra predadores e parasitoides, através do efeito da diluição do ataque entre os indivíduos do grupo. O parasitoidismo foi mais expressivo em larvas de primeiros ínstares, enquanto que larvas mais tardias foram mais atacadas por predadores, independente do tamanho da agregação. Por fim, eventos comportamentais que envolvem movimentação da cabeça como exploração e alimentação foram mais perigosos para as larvas de A. monuste orseis em comparação ao repouso e deslocamento, semelhantemente a espécies de hábito solitário. Eventos comportamentais supostamente defensivos foram observados em todos os ínstares e tratamentos. As vantagens da agregação em A. monuste orseis mostraram-se especialmente importantes no estágio de ovo e primeiros ínstares, pela diminuição da mortalidade de ovos e vulnerabilidade larval aos inimigos naturais. Esses benefícios provavelmente sobrepõem-se aos custos, como a competição por interferência observada entre as larvas no final do desenvolvimento. Nossos resultados mostram que o malogro dos ovos e os efeitos dos inimigos naturais constituem fortes pressões seletivas na manutenção da agregação de ovos e larval em A. monuste orseis, a qual confere uma melhor performance do ponto de vista bi-trófico, bem como maior probabilidade de sobrevivência individual sob o ponto de vista tri-trófico. / In insects, the gregarious habit has been shown to improve foraging and defense against predation to both larval and adult stages. Egg clusters could also be beneficial through increased larval hatching. In this study, we tested the hypothesis that egg clusters and larval aggregations of the neotropical butterfly Ascia monuste orseis (Godart, 1819) (Pieridae) - a subspecies that uses Brassicaceae as hosts - lead to several benefits from both bi- and tri-trophic perspectives. Larval and adult performances, food assimilation by the larvae, egg viability, as well as protection against natural enemies were assessed from individuals reared either isolated or aggregated. The behavior of larval aggregations was also examined with respect to predation risk, as well as the corresponding larval defensive behaviors after enemy attack. Four treatments with different larval aggregation sizes were assigned (1, 7, 15 e 30 larvae) to assess larval performance and food utilization in the laboratory. In the field, three treatments were assigned (1, 10 e 50 larvae) to evaluate the effects of group size on predation and parasitoidism. Egg performance was examined through egg clusters of different sizes in a greenhouse. Gregarious larvae developed faster, especially in early instars, and became more fecund females than solitary larvae; however, the latter attained larger body size than the former. Under laboratory conditions, survival did not differ among treatments. Lower food ingestion per capita was observed in gregarious larvae, with no cost in food assimilation. The viability of eggs increased as egg aggregation size increased. The lower per capita predation in larger larval aggregations than smaller groups conferred higher protection to A. monuste orseis larvae against natural enemies, through the dilution effects among individuals of the group. Parasitoidism was more intense in small-sized larvae while late instars were more susceptible to predators, regardless of aggregation size. Similar to species with solitary habit, behavioral events which involved head movements as searching and feeding were more dangerous to A. monuste orseis larvae compared to resting and walking. Presumed defensive behaviors were observed in all instars and treatments. Thus, the benefits of aggregation in A. monuste orseis can be seen especially in the egg stage and in first instars, as it reduces egg mortality and larval vulnerability to natural enemies. These benefits probably overcome some costs, such as interference competition in the late instars. Taken together, the results show that egg failure and top-down effects constitute selective pressures in maintaining egg and larval aggregation in A. monuste orseis, by providing better performance from a bi-trophic perspective and increased probability of individual survival from a tri-trophic perspective when compared to solitary individuals.

Made available in DSpace on 2016-04-28T14:57:34Z (GMT). No. of bitstreams: 1 2008 - Michela Rocha Leal.pdf: 1770488 bytes, checksum: ff08296ce37cf068a0dc9d932b804f1f (MD5) Previous issue date: 2008-07-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The government of Rio de Janeiro State is encouraging the expansion of fruit crops in the northern region of the State. However, data about ecological aspects of these insects necessary to their suitable management are not available for this region. With the introduction of the parasitoid Diachasmimorpha longicaudata in Brazil, open the perspective of biological control of theses flies. In this context, the present work has as general objectives to increase the knowledge about the geographic distribution of the fruit flies and their ecological aspects in the northern region of this state, and to evaluate the potential of D. longicaudata to biological control of theses flies in this region. These approaches were in the Chapters I and II, respectively. In the chapter I, the studies aimed to know the species of fruit flies of occurrence in the northern region of Rio de Janeiro state, their host plants and their parasitoids; to evaluated the susceptibility of guava variety Paluma to infestation by fruit flies; to characterize the population structure of these tephritids to determine the principal species of occurrence and to evaluate their diversity standard; and to determine the times of the year of higher and lower occurrence of these flies in the region. This study was carried out from April/2006 to May/2007 in Campos do Goytacazes, S?o Francisco do Itabapoana and S?o Jo?o da Barra, being the specimens captured by McPhail traps and collected from fruits. From the captured adults, 93% belong to the genus Anastepha (total of 16 species) and 7% of Ceratitis capitata. A. fraterculus, A. obliqua, A. pseudoparallela, A. serpentina, A. sororcula, A. zenildae and C. capitata infested fruits among 12 wild species. A. fraterculus, A. sororcula and A. zenildae infested guavas of variety Paluma. The populations of frui flies present low diversity of species due to presence of three predominant species: A. obliqua, A. fraterculus and A. sororcula, which occurred during all months of the year, with higher population levels between the summer and autumn due to the influence of higher availability of host fruits in these seasons of the year. The native parasitoids were Doryctobracon areolatus and Aganaspis pelleranoi. In the chapter II, the studies aimed to evaluate the survival capacity and action radius of D. longicaudata 24 hours after its release in the field; and to evaluate the recovered possibility of their offspring from guava samples. In May/2008, D longicaudata was released in a guava orchard in S?o Jo?o da Barra. Thereupon this release, 25 parasitism units containing larvae of C. capitata were spread at the guava trees at 10 m and 20 m from the released point. A sample of guavas was collected on the released day, and 24 hours after this release, another sample of guavas was collected at 30 m from this point. After 24 hour of the release, it was observed the visitation of D. longicaudata in the majority of the parasitism units. Male and female descendants of D. longicaudata were recovered form these parasitism units. A. fraterculus and A. sororcula infested the guavas, from which D. longicaudata was not recovered. / O governo do Estado do Rio de Janeiro vem incentivando a expans?o da fruticultura na regi?o norte do Estado, mas esta corre o risco de sofrer s?rios preju?zos devido ao ataque de moscas-das-frutas. Por?m, dados sobre aspectos ecol?gicos desses insetos, necess?rios para seu manejo adequado, n?o est?o dispon?veis para essa regi?o. Com a introdu??o do parasit?ide Diachasmimorpha longicaudata no Brasil, abre-se a perspectiva de controle biol?gico dessas moscas. Nesse contexto, o presente trabalho teve como objetivos gerais aumentar o conhecimento sobre a distribui??o geogr?fica das moscas-das-frutas seus aspectos ecol?gicos no norte fluminense, e avaliar o potencial de D. longicaudata para o controle biol?gico dessas moscas nessa regi?o, sendo esses temas abordados nos Cap?tulos I e II, respectivamente. No cap?tulo I, os estudos tiveram os seguintes objetivos: conhecer as esp?cies de moscas-das-frutas de ocorr?ncia no norte fluminense, suas plantas hospedeiras e seus parasit?ides; avaliar a susceptibilidade da goiaba variedade Paluma ? infesta??o por moscas-das-frutas; caracterizar a estrutura populacional desses tefrit?deos para determinar as principais esp?cies de ocorr?ncia e avaliar seu padr?o de diversidade; e determinar as ?pocas do ano de maior e menor ocorr?ncia dessas moscas na regi?o. Esse estudo foi conduzido de abril/2006 a maio/2007, em Campos dos Goytacazes, S?o Francisco do Itabapoana e S?o Jo?o da Barra, sendo os esp?cimes capturados por armadilhas McPhail e coletados de frutos. Dos adultos capturados, 93% pertencem ao g?nero Anastrepha (total de 16 esp?cies) e 7% ? Ceratitis capitata. A. fraterculus, A. obliqua, A. pseudoparallela, A. serpentina, A. sororcula, A. zenildae e C. capitata infestaram frutos entre 12 esp?cies silvestres. A. fraterculus, A. sororcula e A. zenildae infestaram goiabas da variedade Paluma. As popula??es de moscas-das-frutas apresentaram baixa diversidade devido ? presen?a de tr?s esp?cies predominantes: A. obliqua, A. fraterculus e A. sororcula, que ocorreram o ano todo, com maiores n?veis populacionais entre o ver?o e o outono, pela influencia da maior disponibilidade de frutos hospedeiros nessas esta??es do ano. Os parasit?ides nativos foram Doryctobracon areolatus e Aganaspis pelleranoi. No cap?tulo II, os estudos tiveram os seguintes objetivos: avaliar a capacidade de sobreviv?ncia e raio de a??o de D longicaudata 24 horas ap?s sua libera??o no campo; e avaliar a possibilidade de recupera??o de seus descendentes a partir de amostras de goiaba. Em maio/2008, realizou-se a libera??o de D longicaudata num pomar comercial de goiaba em S?o Jo?o da Barra. Logo ap?s a libera??o, 25 unidades de parasitismo contendo larvas de C. capitata foram distribu?das nas goiabeiras a 10 m e 20 m do ponto de libera??o. Uma amostra de goiabas foi coletada no dia da libera??o, e 24 horas ap?s, coletou-se outra amostra de goiabas a 30 m a partir desse ponto. Ap?s 24 horas da libera??o, verificou-se a visita??o de D. longicaudata na maioria das unidades de parasitismo. Recuperaram-se descendentes machos e f?meas de D. longicaudata a partir dessas unidades. A. fraterculus e A. sororcula infestaram as goiabas, das quais n?o foi recuperado D. longicaudata.