Can the predatory mites Amblyseius swirskii and Amblyseius eharai reproduce by feeding solely upon conspecific or heterospecific eggs (Acari: Phytoseiidae)?

Abstract

The phytoseiid mite, Amblyseius swirskii (Athias-Henriot) is an exotic biological control agent of mites and small insect pests in China. Amblyseius eharai (Amitai & Swirski), on the other hand, is a native predacious mite common throughout East and South-East Asia and considered to be an important natural enemy of Panonychus citri (McGregor). Understanding the ways introduced predators affect native ones is vital if we wish to use the former as biological control agents in the field. In order to evaluate the interactions between these two predacious mites, we observed their life histories when they cannibalized or fed upon intraguild prey under laboratory conditions. Both male and female A. eharai and A. swirskii could develop to adulthood by feeding upon both conspecific and heterospecific (IGP) eggs. However, A. swirskii females supplied with IGP eggs had shorter developmental durations, higher fecundity, and higher intrinsic rates of increase (rm) than those supplied with conspecific eggs. On the other hand, A. eharai females supplied with conspecific eggs had higher rm than those supplied with heterospecific eggs, suggesting that A. eharai females may prefer to prey upon conspecific immatures, even when A. swirskii immature stages are present. As a result, A. swirskii females may decrease A. eharai populations, when extra-guild prey species, such as spider mites, and pollen are scarce.