INTERSPECIFIC AND INTRASPECIFIC PREDATION ON IMMATURES BY ADULT FEMALES IN EUSEIUS-FINLANDICUS, TYPHLODROMUS-PYRI AND KAMPIMODROMUS-ABERRANS (ACARI, PHYTOSEIIDAE)

In a series of experiments, the interspecific predation and cannibalis m on immatures by the adult females of Euseius finlandicus, Kampimodro mus aberrans and Typhlodromus pyri were examined under laboratory cond itions. The three species showed differing tendencies to prey on each other's motile immature stages. Euseius finlandicus females consumed m ore larvae and protonymphs than the females of T. pyri and K. aberrans . In cages without free water E. finlandicus ate a range of 6.51 larva e or 5.31 protonymphs of T. pyri and 5.27 larvae or 5.95 protonymphs o f K. aberrans per female per day. Kampimodromus aberrans and T. pyri f emales exhibited a greater tendency to prey on heterospecifics than on conspecifics. When feeding on phytoseiid immatures and without free w ater, T. pyri females survived longer and laid more eggs than the fema les of E. finlandicus and K. aberrans. Adult females of E. finlandicus and T. pyri having free water and preying on heterospecific protonymp hs were able to maintain egg laying during the whole experimental peri od of 12 days. The females of all three species had difficulties in pi ercing phytoseiid eggs, and the number of sucked eggs per female per d ay was low. Kampimodromus aberrans females ate 0.48 eggs of T. pyri da ily, which was the highest recorded number. The great tendency to inte rspecific predation on motile immature phytoseiids by the females of E . finlandicus is discussed with regard to the dominance of this specie s on deciduous trees and bushes in Austria.