Allothrombium pulvinum Ewing is one of the important species of the family Trombidiidae in North, North East and North West of Iran and is an important natural enemy of a variety of pest species. Larvae emerge in spring and are ectoparasitic of aphids. Inthis study the effects of A. pulvinum larvae on adult aphids (alatae) of Hyalopterous amygdali Geoff. on apricot leaf discs at different aphids: mite ration consist of 1:0, 1:1, 1:2, 1:3, 1:4 and 1:5 were studied. Each treatments was repeated five times and all tests of significance wre made at levels of 5% and 1%, using F test. The results of analysis of the survival time and number of progeny among various treatments showed that there was very significant variation among treatments (F=3.65, df=5.29, P=0.01), exept for no significance for the comparison among treatments of aphid: mite ratios 1:3, 1:4 and 1:5. When the mites load were five, four and three, A. pulvinum larvae killed all adults of H. amygdali within three days. This indicated that the presence of more than 2 mites per H. amygdali adult (alatae) could cause great reduction in the survival and reproductive rates of parasitized aphids. All experiments were carried out in a growth chamber (22±1˚C, 75±5% R.H. and 12L:12D).

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