An Evaluation of the Predatory Function of Orius strigicollis (Poppius) (Hemiptera: Anthocoridae) on Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae)

<i>Megalurothrips usitatus</i> (Bagnall) is one of the most important pests harming alfalfa (<i>Medicago sativa</i> L.) in Ningxia. In the field, <i>Orius strigicollis</i> (Poppius) is abundant. It has a high search efficiency and consumption rate of prey on a wide range of thrips and is often used as a biological control agent for these insects. To understand the predatory function and biological control potential of <i>O. strigicollis</i> on <i>M. usitatus</i>, the predatory ability of adults of <i>O. strigicollis</i> on second-instar larvae and adults of <i>M. usitatus</i> was measured under indoor conditions, and the Holling II and Hassell-Varley models were fitted to calculate the predatory function response, search efficiency, intraspecific interference, and predation preference of <i>O. strigicollis</i> on second-instar larvae and adults of <i>M. usitatus</i>. Our results showed that the predatory ability of <i>O. strigicollis</i> on second-instar larvae of <i>M. usitatus</i> was 78.62, and the theoretical maximum daily predation was 76.92. The predatory ability of <i>O. strigicollis</i> on adults of <i>M. usitatus</i> was 52.79, and the theoretical maximum daily predation was 52.62. The daily predation of <i>O. strigicollis</i> was positively correlated with prey density and negatively correlated with search efficiency. The rate of predatory action on prey decreased with an increasing <i>O. strigicollis</i> density, while the intensity of apportioned competition increased with an increasing <i>O. strigicollis</i> density. The results of the prey preference experiment showed that the preference of <i>O. strigicollis</i> for second-instar larvae of <i>M. usitatus</i> was significantly higher than for adults of <i>M. usitatus</i>. In conclusion, the indoor experiment data can provide an effective reference for the use of <i>O. strigicollis</i> to control <i>M. usitatus</i> infestation, providing an important biological control agent for controlling <i>M. sativa</i> thrips.