Intraguild predation and cannibalism among Dicyphini:Dicyphus cerastiivs. two commercialized species

Dicyphine mirids are one of the most important groups of predators on tomato. In the Mediterranean region, several species in the generaDicyphus,Macrolophus, andNesidiocoris(Hemiptera: Miridae, Bryocorinae, Dicyphini) colonize protected horticultural crops. In Portugal,Nesidiocoris tenuis(Reuter) is increasingly abundant in the mirid species complex of tomato crops and appears to be displacing the nativeDicyphus cerastiiWagner. In order to know whether intraguild predation (IGP) can explain the decreasing abundance ofD. cerastii, we evaluated predatory interactions between adult females and first instars ofD. cerastiivs.N. tenuisbut alsoD. cerastiivs.Macrolophus pygmaeus(Rambur), as this species is also naturally present in horticultural crops in Portugal. Cannibalistic interactions were also tested for the same three species. All experiments were performed under laboratory conditions, in Petri dish arenas, in the presence or absence ofEphestia kuehniellaZeller (Lepidoptera: Pyralidae) eggs as alternative prey. Predation on both heterospecific and conspecific nymphs occurred only in the absence of alternative food. Intraguild predation was mutual and symmetrical betweenD. cerastiiandM. pygmaeus. However, IGP was asymmetrical betweenD. cerastiiandN. tenuis, favouring the first. Cannibalism was not significantly different among these mirid species. Our results show thatD. cerastiihas a greater capacity to feed on intraguild prey thanN. tenuis. Therefore, IGP on small nymphs does not explain the abundance shift betweenD. cerastiiandN. tenuis.