Abstract: The use of the predatory mirids Macrolophus pygmaeus and Nesidiocoris tenuis forthe control of arthropod pests on greenhouse tomatoes is at present limited in someMediterranean regions by factors of an economic and technical nature. To assess the influence ofthe production and distribution process, the availability of a supplementary food source andseasonal climatic trends in the reproductive fitness of the two mirid species, some laboratory andsemi-field experiments were conducted during the last year. The adverse effects of the stressexperienced by commercially supplied insects have clearly emerged through the investigation,but at different levels of intensity for the sources tested. The supply of Ephestia kuehniella eggshas shown pronounced effects on the reproductive fitness of the predatory mirids, in some casesallowing a partial recovery of fertility in stressed individuals and confirming the suitability ofsupplementary food sources in improving mirid performances. Furthermore, the results of thetests carried out appear to indicate that M. pygmaeus is more suitable for winter releases inSardinian tomato greenhouses, whereas N. tenuis is to be preferred for autumn releases.