Biological characteristics of the mirids Macrolophus costalis and Macrolophus pygmaeus preying on the tobacco form of Myzus persicae (Hemiptera: Aphididae).

Biological and population parameters of the predatory bugs Macrolophus costalis Fieber and Macrolophus pygmaeus Rambur preying on the tobacco aphid Myzus persicae (Sulzer) were examined. Tobacco was used as host plant and all experiments were carried out at 23 degrees C and L16:D8. In M. costalis, the developmental time for eggs and the total duration of nymphal instars was 13.1 and 22.2 days and in M. pygmaeus 13.0 and 20.2 days, respectively. Both species completed their nymphal development feeding only on plant juices although they required significantly more time to attain adulthood than when feeding on prey. The longevity of M. costalis females and the preoviposition period were 49.9 and 5.6 days and those of M. pygmaeus were 50.3 and 6.3 days, respectively. Adult males showed a higher longevity than females in both species. The intrinsic rate of increase and the mean total number of eggs laid were 0.0644 and 121 in M. costalis and 0.0615 and 104 in M. pygmaeus, respectively. Mean total aphid consumption by nymphs of M. costalis was 61 aphids, about twice that of M. pygmaeus (37 aphids). Total aphid consumption by a male and female pair of M. costalis and M. pygmaeus until the death of the female was 244 and 285 aphids, respectively. The results of the study are discussed in relation to the impact of the two predatory bugs on tobacco aphid populations.

Discrimination of the closely related biocontrol agents Macrolophus melanotoma (Hemiptera: Miridae) and M. pygmaeus using mitochondrial DNA analysis.

The separation of the closely related predatory species Macrolophus melanotoma Costa (= M. caliginosus Wagner) and Macrolophus pygmaeus (Rambur) based exclusively on the different colour pattern of the first antennal segment (white central band in M. melanotoma and entirely black in M. pygmaeus) is rather precarious and their taxonomic status is still in doubt. In the present study their taxonomic status was evaluated by DNA confirmatory analysis and hybridization experiments between M. pygmaeus and a Macrolophus taxon, resembling M. melanotoma, with a first antennal segment entirely black or with a white central band collected from Dittrichia viscosa (L.) W. Greuter (Asteraceae) in southern Greece. Adult females from Dittrichia plants hybridized with males of M. pygmaeus and vice versa did not produce viable eggs. The Macrolophus species from Dittrichia irrespective of the first antennal segment coloration differed from M. pygmaeusin digestive patterns generated by AseI, XbaI, and MseI on 16S rRNA and in RAPD profiles produced by the primers OPA-18 and OPA-20. These results demonstrate that on Dittrichia plants there is a distinct dimorphic taxon, M. melanotoma, as it is the only species of the genus Macrolophus bearing a first antennal segment with a central white band. Given the limitation of the coloration pattern, the mtDNA genetic markers are the appropriate method for the identification of M. melanotomaand M. pygmaeus.