Life history of the two phytoseiid species Amblyseius scutalis (= Euseius scutalis (A.‐H.) and A. swirskii A.‐H. was studied at constant conditions 26 ± 1 °C and 70% ± 3 RH to compare their life tables and effeciency as biological control agents. Developmental stages of mite female of both A. scutalis and A. swirskii fed on nymphs of Tetranychus urticae Koch durated 7.81 and 5.50 days, respectively. Preoviposition, oviposition and postoviposition periods lasted 2.86 and 1.87; 12.86 and 22.33; 11.40 and 5.12 days for the two mite species, respectively. The intrinsic rate of natural increase (rm) and finite rate of increase (Λ) were 0.146 and 0.167; and 1.15 and 1.18; while the net reproductive rates (R0) were 7.22 and 12.97; and the mean generation time (T) was 14.68 and 16.97 for A. scutalis and A. swirskii, respectively. Total fecundity as well as total prey consumption of A. swirskii significantly surpassed those of A. scutalis. Zusammenfassung Lebenstafelparameter von Amblyseius scutalis (Athias‐Henriot) und A. swirskii A.‐H. (Acari, Phytoseiidae) in Ägypten Die Biologie der beiden räuberischen Milben, Amblyseius scutalis (= Euseius scutalis A.‐H.) und A. swirskii A.‐H. wurde bei konstanten Laborbedingungen von 26 ± 1 °C und 70% ± 3 Luftfeuchtigkeit untersucht, um verschiedene Parameter dieser beiden Arten hinsichtlich ihrer Wirksamkeit für die biologische Schädlingsbekämpfung zu vergleichen. Die Entwicklungsstadien der weiblichen Milben beider Arten leben räuberisch von den Nymphen von Tetranychus urticae Koch, und ihre Entwicklungsdauer beträgt 7,81 bzw. 5,5 Tage. Die Dauer der Präoviposition, der Eiablagezeit und der Postoviposition beträgt bei A. scutalis 2,86; 12,86 und 11,40 Tage; bei A. swirskii 1,87; 22,33 und 5,12 Tage. Die wirkliche Wachstumsrate (rm) beträgt 0,146 (A. scutalis) bzw. 0,167 (A. swirskii) und die finite Wachstumsrate (λ) 1,15 bzw. 1,18. Die Nettoreproduktionsrate (Ro) liegt bei 7,22 bzw. 12,97 und die mittlere Generationszeit (T) bei 14,68 bzw. 16,97. Hinsichtlich Fekundität und Beutetierkonsum erreichte A. swirskii signifikant höhere Werte als A. scutalis.

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The immature stages of the phytoseiid mite Amblyseius barkeri Hughes are described and illustrated. Incubation period averaged 2.0 ± 0.75 days while female and male total immature stages lasted 8.43 ± 0.8 and 6.86 ± 1.07 days, during which they consumed 9.4 ± 2.3 and 8.43 ± 0.97 Tetranychus urticae Koch nymphs, respectively. The female and male life span averaged 34.70 ± 2.0 and 24.8 ± 1.6 days, during which the predator consumed 161.43 ± 13.16 and 106.8 ± 16.42 prey individuals, respectively. During oviposition period, average female attacked 52.92% of the total prey individuals consumed during its longevity, and laid 13.20 ± 0.86 eggs with a daily rate of 1.02 ± 0.26 eggs.

The exotic predaceous mite, Phytoseiulus persimilis Athias-Henriot and the 2 native ones Phytoseius finitirnus Ribaga and Amblyseius gossipi Elbadry were released on greenhouse cucumber plants in Egypt to examine their efficiency to control the twospotted spider mite Tetranychus urticae Koch. P. persimilis proved to be sufficiently effective for the twospotted spider mite control under greenhouse conditions in Egypt. The 2 before-mentioned native predators were lost soon after release in the greenhouse although they are key mite predators on outdoor crops in this area. KEY-WORDS : Phytoseiulus persimilis, Phytoseius finitimus, Amblyseius gossipi, Tetranychus urticae, greenhouse, release.Chemical control is still the primary method used to control the twospotted spider mite Tetranychus urticae Koch on vegetables grown in greenhouses in Egypt. Phytotoxicity and the loss of efficacy as a result of resistant pest populations are the major problems encountered. Moreover, it was observed that plants are more damaged from the excessive application of pesticides than they are by the pests themselves.Considerable advancements have been achieved in biological control of mites infesting greenhouse crops in different areas through the release of the predatory mites Phytoseiulus persimilis Athias-Henriot and P. macropilis (Banks) (Hamlen & Lindquist, 1981 ;Osborne et al., 1985; Vacante & Nucifora, 1987). In the present study, P. persimilis (OP-resistant strain, originally from GDR) was introduced into Egypt and released on greenhouse cucumber.For comparison, the use of the 2 native predaceous mites Phytoseius finitimus Ribaga and Amblyseius gossipi EIbadry for mite control was also evaluated. The last 2 predators were found to be effective on outdoor crops (Rasmy & Elbanhawy, 1974 ; Rasmy, 1977). MATERIALS AND METHODSP. persimilis was mass-reared on the twospotted spider mite maintained on bean plants. P.finitimus and A. gossipi were taken from a colony fed pollen grains of castor bean Ricinus communis L. P. persimilis was released on a bed of 200 plants, while another bed of an equal number of plants was left as a check. For comparative studies, each of the other 2 predators was released on a group of 100 plants. Release of predators was carried out at a rate of 10 predators per plant at the 1st sign of the twospotted spider mite damage, when slight discoloration of leaves was observed. The predators were introduced on the remarkably infested leaves.For assessing mite populations, 5 leaves of each treatment were investigated at weekly intervals and the number of mites was recorded. When P.finitimus and A. gossipi were not encountered on leaf samples, a supplementary release with these 2 predators was conducted after 2 weeks of the 1 st release to ensure their establishment. RESULTS AND DISCUSSIONAlthough the 2 native predators P.finitimus and A. gossipi are the key mite predators on several outdoor crops in Egypt, both predators did not develop successfully under greenhouse conditions. In fact they were lost soon after rele...

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