Intra- and interspecific predation among adult female phytoseiid mites (Acari: Phytoseiidae): Effects on survival and reproduction

We tested whether the oligophagous phytoseiid mites Metaseiulus occidentalis (Nesbitt) and Neoseiulus fallacis (Garman) differed in predation, survival, and reproduction from the polyphagous mites Typhlodromus pyri Scheuten and Amblyseius andersoni Chant when cohorts of adult females (no immatures) of each were held without food at a ratio of 40:0 or in all combinations at 20:20 or 10:10:10:10. When alone, mean survival was 5-10 cl: T. pyri > A. andersoni > M. occidentalis > N. fallacis. Of the 4, only M. occidentalis did not feed interspecifically on live adult females, all 4 scavenged dead mites. At 20:20, A. andersoni killed ?: pyri least rapidly, M. occidentalis most rapidly. Both T. pyri or N. fallacis killed a few M. occidentalis. A. andersoni survived longer with either M. occidentalis or N. fallacis than with ?: pyri. A, andersoni adult females when held with 20 ill. occidentalis adult females (replaced daily) produced 33-50% fewer progeny than with twospotted spider mite, Tetranychus urticae Koch, adult females; this was much more than with ?: pyri or N. fallacis adult females. Neither T. pyri nor N. fallacis adult females produced new adults when held with M. occidentalis adult females. It is clear that some adult female phytoseiids can feed on others and add to their survival and reproduction. No clear patterns mere seen in the predation responses of oligophagous versus polyphagous species.