How omnivory affects the survival and choices of earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae)?

Doru luteipes (Scudder, 1876) is an omnivorous predator that finds different food resources in the corn plant: eggs of Spodoptera frugiperda (J.E. Smith, 1797), uredospores of Puccinia polysora (Underw, 1897), and pollen. Knowing the survival and food preferences of this predator is essential to define its relevance as a biological control agent. We hypothesize that the foraging behavior and predatory capacity of D. luteipes may be affected when several food resources, especially eggs of S. frugiperda, uredospores of P. polysora, and pollen are concurrently in the same plant. The survival of D. luteipes in the nymph stage and their preference among food resources, often available in corn plants, were determined. To verify the survival of D. luteipes, newly hatched nymphs were fed exclusively with 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- a combination of uredospores + eggs, and 5- artificial diet (control). In another experiment, nymphs and adults of D. luteipes with 24 and 48 hours of fasting were individually released in the center of a container with four diets: 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- artificial diet, and maintained for 10 minutes, to evaluate the food choice and feeding time. The exclusive feeding with S. frugiperda eggs caused low nymph survival (8%), but the combination of P. polysora uredospores + S. frugiperda eggs allowed 58.3% survival. D. luteipes preferred feeding during the nighttime and the most significant proportions of choices by nymphs and adults were for pollen and diet, with adults spending more time eating pollen. These findings indicate that the trophic choices of D. luteipes are relevant to understand its contribution as an agent to control pest insects and fungal diseases in corn.

Influence of Feeding with different Plant Pollens on Prey- Stage Preference and Predation Rate of Neoseiulus Californicus (Mcgregor) (Acari: Phytoseiidae)

Neoseiulus californicus (Acari: Phytoseiidae) is an effective predator in greenhouses which feeds on plant injurious mites. Searching capacity is one of importance in the effectiveness of this predatory mite. In this research, the population fed with corn pollen, walnut and date pollen and the spider mite (four strains) were investigated. The prey-stage preference of N. californicus was studied on different developmental stages of Tetranychus urticae. The predation rate of rearing population of N. californicus was determined; it was used eggs of T. urticae. Experiments were carried out on strawberry disc in Petri dish (6 cm diameter) under laboratory conditions (27±1ºC temperature, 70±5% RH and 16L: 8D photoperiod). After 24 hours, the total numbers of prey consumed were counted. The predatory mites reared on different pollens prefer eggs or nymphs to adults and the Preference Index of different strains was not different. Result of consumed of spider mites by female predatory mites indicated the predation rate of the predatory mites fed with corn pollen (9±1.46), walnut pollen (8.19±0.99) and Date pollen (8.28±0.80) did not any significant difference, however when spider mites and the mentioned pollens were used, the predation rate of predatory mites when fed with T. urticae (14.74±0.94), Walnut (15.24±1.05) and date pollen (14.17±1.04) show significant difference with the population of corn pollen (10.0±0.95). The predation rate of four strains decreased at present of plant pollens. Use of the predatory mite fed with the different developmental stage of two-spotted spider mite and pollen in the biological control of the pests is useful.