It is largely known that the range of an insect diet is mostly determined by oviposition behavior, mainly in species with endophytic larvae such as Zabrotes subfasciatus. However, the proximate factors determining host choice and the subsequent steps leading to the expansion or reduction of the host number and occasional host shifts are largely unknown. We analyzed various factors determining host preference of Z. subfasciatus through the evaluation of: (i) oviposition preference of a wild population of Z. subfasciatus on the usual host (bean) and unusual hosts (lentil, chickpea and soy), and the performance of the offspring; (ii) artificial selection for increasing preference for hosts initially less frequently chosen; (iii) comparison of oviposition behavior between two different populations (reared for ~30 generations in beans or chickpeas, respectively); (iv) oviposition timing on usual and unusual hosts; and (v) identification of preference hierarchies. We found that when using unusual hosts, there is no correlation between performance and preference and that the preference hierarchy changes only slightly when the population passes through several generations on the less frequently accepted host. We also found a positive response to artificial selection for increasing oviposition on the less preferred host; however, when the host-choice experiment involved two varieties of the usual host, the response was faster than when the choice involved usual and unusual hosts. Finally, beetles reared on an unusual host (chickpea) for 26 generations showed similar good fitness on both usual and unusual hosts, indicating that the use of a new host does not necessarily result in the loss of performance on the original host. Nevertheless, this population showed lower fitness on the usual host than that of the original population, suggesting an underlying partial trade-off phenomenon which may contribute to a broadening of diet of this insect species.
Income breeding animals support reproduction by the intake of energy and molecular building blocks during adulthood. Capital breeders, in contrast, fuel reproduction by the intake of materials during the larval stage. There exists, however, some controversy as to whether adult feeding in capital breeders actually increases fitness. We tested whether individuals feed as adults in the weevil Zabrotes subfasciatus Boheman, whether they equally accept carbohydrate‐ or nitrogen‐rich food (sugar or yeast), whether food ingestion varies with the available host type and whether feeding as adults alters life history traits. The hosts tested were three varieties of Phaseolus vulgaris, Carioca, Jalo, and Preto; Vigna unguiculata Frade; and Vicia faba. We also tested whether sugar ingestion affects life history traits differently in the presence of different host types. We found that Z. subfasciatus feed as adults and equally accept sugar and yeast, and food ingestion depends on host type. Sugar and yeast significantly promote oviposition of larger eggs on Carioca seeds and enhance adult emergence, and sugar ingestion increases longevity. Moreover, the insects avoid feeding when on V. faba seeds, on which they did not oviposit. Mean fitness values showed the following hierarchy: Carioca = Jalo > Frade > Preto > V. faba. These results show that the capital breeder Z. subfasciatus feed as adults, which increases life history traits and suggests the existence of a hierarchy of performance on different hosts, with the P. vulgaris varieties Carioca and Jalo offering the best conditions.
RESUMOO monitoramento de populações de Lepidoptera fornece informações importantes para avaliar a dinâmica e as mudanças ecológicas nos ecossistemas. Neste trabalho avaliou-se e caracterizou-se a Lepidofauna da mata do IFSULDEMINAS -Campus Muzambinho -MG, estabelecendo um padrão para inúmeros fragmentos semelhantes na região. ABSTRACTThe monitoring Lepidoptera populations provides important information to assess the dynamics and ecological changes in ecosystems. In this work, it was evaluated and characterized the Lepidoptera fauna of forest fragment of the IFSULDEMINAS -Campus Muzambinho, MG state. Throughout 12 months, 590 Individuals of 69 species belonging to 10 families were captured. The most abundant family was Nymphalidae (73.56% of subjects). The most abundant species were Godartiana muscosa, Mechanitis lysimnia, Hermeuptychia sp and Mechanitis polymnia casabranca, which are bio-indicators of disturbed and/or urban environments. On the other hand, it was found rare species, such as Notascea brevispula. Different species were constant and others occurred in only a short period of the year. The diversity and abundance were higher in hot and rainy months. The diversity index Shannon-Wiener and Simpsom indicate a median diversity and equitability index point absence of dominance.
ResumoSabe-se que uma grande porcentagem da produção e do armazenamento dos grãos de feijão é perdida pelo consumo de insetos. Este trabalho teve como objetivo avaliar a atividade inseticida do óleo essencial de Hyptis marrubioides no controle de Zabrotes subfasciatus. A extração do óleo essencial foi realizada pelo método de hidrodestilação em aparelho de Clevenger, por uma hora e meia e o ensaio biológico foi conduzido no Laboratório de Microscopia/IFSULDEMINAS, Campus Muzambinho. O delineamento experimental utilizado foi inteiramente casualizado, constituído de cinco concentrações de óleo essencial (0,0; 6,25%; 12,5%; 25% e 50%), com quatro repetições contendo um casal de Z. subfasciatus por repetição. Realizou-se o teste de mortalidade e inibição de oviposição. Utilizou-se três grãos de feijão tratados com 5 microlitros (μL) de solução e três não tratados, caracterizando assim um teste com chance de escolha. Como controle, utilizou-se 100 μL de álcool 70%. Após a aplicação dos tratamentos, observou-se a reação dos indivíduos de Z. subfasciatus, evidenciando que os Tempos Letais (TL) diminuem conforme há um aumento e contato direto dos insetos com as concentrações do óleo essencial de H. marrubioides. A aplicação do óleo essencial foi bastante efetiva, pois ocorreu mortalidade total dos insetos adultos e nenhuma oviposição. O intervalo de tempo de 28 minutos foi suficiente para provocar mortalidade de todos os indivíduos. Foi possível observar que o óleo essencial de H. marrubioides possui efeito inseticida sobre Z. subfasciatus, podendo auxiliar no manejo integrado de Z. subfasciatus em feijão armazenado.Palavras-chave: Hortelã-do-campo. Planta medicinal. Inseticida natural. Caruncho-do-feijão.
Avaliou-se a preferência alimentar do besouro Tribolium castaneum na farinha de soja integral, sendo que o seu substrato usual é a farinha de milho. Foram utilizados 3 tipos de substratos: farinha de milho, farinha de trigo e farinha de soja integral, placas de Petri com divisória tripla e sem divisórias, estufa entomológica equipada a 32ºC de temperatura e 70% de umidade relativa do ar. Foram colocados na placa de Petri com divisória 2 g de cada substrato e 6 besouros num total de 18 besouros na estufa entomológica, mantidos neste local por 5 dias. Posteriormente, os insetos foram retirados e foi mantida a placa de Petri na estufa entomológica por mais 15 dias para serem contadas as larvas e, entre 21-28 dias, foram observados os adultos emergidos, completando, assim, o ciclo. O mesmo procedimento foi efetuado para a placa de Petri sem divisória, utilizando somente um tipo de substrato. Pode-se observar no experimento que enquanto na farinha de milho e farinha de trigo havia presença de besouros, na farinha de soja havia presença de larvas. As fêmeas foram perfeitamente capazes de ovipositar em outro hospedeiro, desde que esse contivesse os componentes nutricionais necessários para o desenvolvimento, o que permitiu que o inseto se adaptasse a diferentes situações de disponibilidade de alimento.
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