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During a laboratory biological study of a midge, Feltiella acarisuga (Vallot, 1827) (Diptera: Cecidomyiidae), acarivorous on two-spotted spider mites, some ceraphronid specimens were reared from the midge cocoons. A detailed morphological study and comparison with previously known species revealed that the ceraphronid is a new species of Aphanogmus Thomson, 1858 (Hymenoptera: Ceraphronidae). The new species is described as A. feltiellophagus Lotfalizadeh, sp. nov. and compared with closely related species. An identification key for all Aphanogmus species associated with predatory cecidomyiids is provided. As a parasitoid of the pupal stage of Feltiella acarisuga, the potential negative impact of A. feltiellophagus on the biological control of tetranychid mites is discussed.

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Prey suppression by predators depends on effective predator: prey release ratios. The effectiveness of Phytoseiulus persimilis Athias-Henriot and Typhlodromus bagdasarjani Wainstein and Arutunjan was evaluated at different predator: prey release ratios for suppression of Tetranychus urticae Koch populations on cucumber plants in the microcosm condition based on three experiments. In the first experiment, 7 days after T. urticae releases, the most reduction in the different stages (densities) of T. urticae and the most increase in both P. persimilis and T. bagdasarjani were observed in predator: prey release ratio of 1:4 followed by ratios of 1:10 and 1:20. In the second experiment, one day after T. urticae release at predator: prey release ratio of 1:4, there was no significant difference between predators effect on the decline of T. urticae stages (densities). In this case, more T. bagdasarjani at all stages was observed on the plants in comparison with P. persimilis. According to the third experiment, 7 days after T. urticae release, there was no significant difference between predator: prey ratio of 1:4 of P. persimilis and 1:2 of T. bagdasarjani on T. urticae suppression. In this case, more P. persimilis was observed on plants in comparison with T. bagdasarjani. Our study demonstrates that the most suppression of T. urticae populations occurred in predator: prey ratio of 1:4 for both predators. Based on our findings, we suggest that P. persimilis and T. bagdasarjani can be released at a ratio of 1:4 for successful control of T. urticae on cucumber.

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Stethorus gilvifrons (Mulstant) is an important voracious predator of the spider mites, which consumes all the life stages of spider mites. In this study, the effects of prey species and host plants on development and life table parameters of S. gilvifrons were studied. To this end, preimaginal development, survival, adult longevity and fecundity of S. gilvifrons fed on Tetranychus urticae Koch (on maize and cowpea) and Eutetranychus orientalis Klein (on castor bean plants) were studied. Experiments were conducted based on two-sex life table procedure under laboratory conditions at 27±1°C, 60–70% RH and 16:8 hours L:D. The shortest developmental time and female longevity were recorded on maize and cowpea, respectively, and the longest was on castor bean. While the lowest values of fecundity, net Reproductive rate (R₀) and intrinsic rate of increase (r) were estimated at 107.65±11.49 offspring, 20.63±4.41 offspring and 0.1001±0.0072 d^-1 on castor bean, respectively, the highest values of the mentioned parameters were 158.67±20.18 offspring, 43.63±8.47 offspring, and 0.1448 ± 0.0069 d^-1 on maize, respectively. The results proved the significant effects of the host plants and prey species on developmental time and demographic parameters of S. gilvifrons. The obtained results could be useful for mass rearing of S. gilvifrons and for better understanding of its population dynamics in relation to the prey species and host plants.