Integrated Control in Protected Crops, Mediterranean Climate IOBC-WPRS Bulletin Vol. 80, 2012 pp. 97-101 97 Effect of supplemental food on the fitness of four omnivorous predator species Marta F. Oveja, Judit Arnó, Rosa Gabarra IRTA, Entomology, E-08348, Cabrils (Barcelona), Spain Abstract: The predators Orius laevigatus, O. majusculus, Macrolophus pygmaeus and Nesidiocoris tenuis are extensively used in biological controls in vegetable crops. The fitness and local density of these predators, which are omnivores and feed on arthropods and plants, may be enhanced by the provision of supplemental food, especially when prey is scarce, and this may improve biological control results. The aim of our study was to evaluate the effect of four supplemental foods: Ephestia kuehniella eggs, dry Artemia sp. cysts, the mite Tyrophagus putrescentiae and commercial multifloral bee pollen, on the reproduction and longevity of these four predators. Our results show that using dry cysts of Artemia sp. as factitious prey had positive effects on the reproduction of the predators O. majusculus, O. laevigatus, M. pygmaeus and N. tenuis. Furthermore, dry commercial multifloral bee pollen improved the longevity of the females of O. laevigatus, O. majusculus and M. pygmaeus as much as eggs of E. kuehniella. Dry cysts and dry pollen need little or no handling to prepare them for use, are very easy to disperse in the crop and maintain their quality for a reasonable time. Further experiments need to be conducted under semi-field conditions to better evaluate the positive effect of these two supplemental foods on predator establishment in the crop. It will also be important to evaluate the effect of these foods on life parameters of pest species and on intraguild relationships among predators. Key words: predatory Heteroptera, alternative prey, biological control, reproduction, longevity Introduction The predators Orius laevigatus, O. majusculus, (Hemiptera: Anthocoridae), Macrolophus pygmaeus and Nesidiocoris tenuis (Hemiptera: Miridae) are some of the most common natural enemies used in the biological control of pests affecting vegetable crops. They are extensively used not only in inoculative programmes but also in biological conservation control strategies (Castañé et al., 1999; Arnó et al., 2010). These predators are omnivores and their immature and adult forms can feed on different trophic levels (i.e. other arthropods and plant food such as pollen, nectar or honeydew). This zoophytophagy may satisfy their metabolic and reproductive needs (Coll & Guershon, 2002, Wade et al., 2008; Perdikis et al., 2011). The provision of supplemental food when prey is scarce may increase the individual fitness and local density of these natural enemies in the crop, thus enhancing pest control (Wade et al., 2008). For example, Ephestia kuehniella eggs, which have been extensively used in predator rearing, are recommended to improve early predator establishment in the crop. Some other supplemental foods which are cheaper than E. kuehniella eggs may also improve the reproduction and longevity of predators. These include: other factitious preys used in rearing, like Artemia sp. cysts (Branchiopoda: Artemiidae) or the mite Tyrophagus putrescentiae (Acari: Acaridae) (Husseini et al., 1993, De Clercq et al., 2005, Castañé et al., 2006), or pollen, which enables some predators to sustain reproduction and adult longevity even in the absence of prey (Cocuzza et al., 1997, Vandekerkhove & De Clercq, 2010).