Size and flight ability of Telenomus remus parasitoids reared on eggs of the factitious host Corcyra cephalonica

ABSTRACT In two independent bioassays, size and flight ability of parasitoids reared on eggs of Corcyra cephalonica for 19 generations and parasitoids reared on a natural host (Spodoptera frugiperda eggs) for 250 generations were compared as fast quality control procedures for insect rearing. The size of parasitoids was examined by morphometric analysis using a stereoscope. Length and width of the wings, right hind tibia, and the body of 20 individuals (males and females) were measured. In the analysis of flight ability, parasitoids were divided into three groups: individuals able to fly ("flyers"), individuals that did not fly but had no visible deformation ("walkers"), and individuals with visible deformation ("deformed"). We observed that parasitoids were larger when reared on the natural host than on the factitious host for all evaluated morphological characters. However, there was no significant difference between the treatments regarding the number of "flyers", "walkers" or "deformed" parasitoids. This indicates that even though the rearing of T. remus on a factitious host affects parasitoid size, it does not necessarily affect its flight ability and therefore suggests that C. cephalonica is suitable as a factitious host for mass rearing of T. remus. Other biological parameters still need to be evaluated, such as host finding ability, parasitism capacity, and parasitoid field efficacy in order to provide a more complete picture of the effects caused by a host change. However, because fast laboratory tests are needed in rearing facilities, the one used in this study might be useful to rapidly assess parasitoid quality.

Rearing method of Oryzaephilus surinamensis (L.) (Coleoptera, Silvanidae) on various wheat grain granulometry

Oryzaephilus surinamensis is one of most common insect pest of grains and a variety of stored products, and has been found in high numbers in almost all storage facilities. However, laboratory mass rearing of this insect for bioassays is not a simple task, mainly because of its feeding behavior, small size, and high mobility. Thus, the aim of this work was to develop a simple and efficient laboratory rearing method for O. surinamensis, using wheat kernels milled into different granulometry to obtain large number and standardized population at different life stages for bioassays. The adults were collected from storage grain facilities in the southern region of Brazil and 100 specimens were placed inside glass jars with wheat kernels milled at different grades and kept at 25±0.5ºC and 65±5 percent relative humidity. The insects were allowed to copulate and lay eggs for 10 days and then removed. The number of eggs, larvae, and pupae was counted at five-day intervals; longevity of the second generation adults was evaluated. The kernels milled at grade 20 were the best medium for offspring production: 89 percent of eggs by the 5th day; 30.5 percent larvae by the 10th day; 43 percent pupae by the 30th day and 63.4 percent adults at the 46th day. The adults survived up to 450 days. Culturing O. surinamensis under the described conditions, transferring the parental adults by the 10th day after infestation and replacing the media when population builds up will produce enough insects of each stage for various laboratory bioassays.

Oryzaephilus surinamensis é uma das espécies de insetos-praga mais comuns em grãos e outros produtos armazenados, e tem ocorrido em grandes populações em praticamente todas as unidades de armazenamento de grãos. Contudo, a criação massal deste inseto, em laboratório, para bioensaios diversos, não tem sido uma tarefa simples, em função de seu comportamento alimentar, tamanho reduzido e alta mobilidade. Assim, o objetivo deste trabalho foi desenvolver um método simples e eficiente para a criação de O. surinamensis, usando grãos de trigo moídos a diversas granulometrias para obter grandes populações e estágios padronizados para bioensaios. Insetos adultos foram coletados em diversos armazéns na região sul do Brasil; 100 espécimes foram colocados em frascos de vidro, com grãos de trigo moído a diferentes graus, mantidos a 25±0.5ºC e 65±5 por cento de umidade relativa. Os insetos foram mantidos por 10 dias para cópula e postura dos ovos, sendo então removidos. Ovos, larvas e pupas foram contados a intervalos de cinco dias; a longevidade dos adultos da segunda geração foi avaliada. Os grãos moídos a grau 20 representaram o melhor meio para a produção de progênie: 89 por cento dos ovos foram produzidos no 5º dia; 30,5 por cento das larvas no 10º; 43 por cento das pupas no 30º e aproximadamente 63 por cento dos adultos no 46º. Os adultos sobreviveram até 450 dias. A criação de O. surinamensis, nas condições descritas e transferindo os adultos após 10 dias e repondo o meio quando a população aumenta muito, produzirá um número de insetos de cada estágio suficiente para diversos bioensaios de laboratório.