The impact of the arrival of the exotic coccinellid Harmonia axyridis on the biological control and dispersion of apple mites and aphids, and on the vertical distribution of the established coccinellids Coccinella septempunctata and Coleomegilla maculata have been studied. Assemblages of adults of the three coccinellid species were tested on apple saplings and on apple trees against Aphis citricola and Tetranychus urticae. The presence or substitution of adults of H. axyridis for adults of C. maculata or C. septempunctata did not reduce the predation impact on mite or aphid prey. H. axyridis was a more efficient predator of mites than was C. septempunctata and generated lower prey dispersal from host plants. Substitutions of adults of H. axyridis for those of C. maculata, and in some cases of C. septempunctata, resulted in greater reduction in number of aphids. On apple trees, the three coccinellid species occurred at different heights. Neither C. maculata nor C. septempunctata modified their vertical distribution on apple tree over a 24 hour period in response to the presence of H. axyridis.
The predatory lacewing Dichochrysa prasina Burmeister can feed and reproduce on various aphid species. However, other species such as the two spotted spider mite Tetranychus urticae Koch may serve as an alternative prey for this predator in the field in periods when the population density of aphids is low. In peach orchards in Northern Greece D. prasina larvae are often found during the summer months on leaves infested with T. urticae. The development and reproduction of D. prasina fed on T. urticae at a series of different constant temperatures were studied. The percentages of D. prasina larvae that completed their development when fed on T. urticae ranged from 12 to 60% depending on the temperature over the range from 20 to 30°C, whereas at temperatures above 33°C no larvae survived. Longevity and egg production of D. prasina females fed during the larval stages on T. urticae were also determined and certain demographic parameters such as the intrinsic rate of increase (rm), mean generation time and net reproductive rate were estimated. Over the range of temperatures from 20 to 27°C, the rm values were not significantly different and varied from 0.06629 to 0.07030. Based on the results of the present study, the possible effect of the availability of T. urticae as prey for D. prasina during summer, when its main prey species is scarce, is discussed.