Effect of long-term feeding history on functional and numerical response of Neoseiulus californicus (Acari : Phytoseiidae)

The functional and numerical responses of the predatory mite Neoseiulus cal ifornicus to eggs and protonymphs of Tetranychus urticae were studied on ex cised strawberry leaflet discs under laboratory conditions (25 +/- 1 degree s C, 75-85% RH and 16L:8D). Four strains of the phytoseiid were compared: t hree originated from a long-term mass-rearing with different food (T. urtic ae, Dermatophagoides farinae and Quercus spp, pollen) and under controlled conditions, while the fourth was directly collected from a natural environm ent and therefore considered a wild strain. The different nutritional histo ries affected the responses of N, californicus on tetranychids. On the whol e, the wild strain gave better performance. When egg prey was administered this strain and the one mass-reared on two-spotted spider mites showed simi lar functional as well as numerical responses; on the contrary, when proton ymphs were furnished, the wild strain did not differ from that mass-reared on pollen. The strain previously fed on house dust mites gave the worst per formance and also showed the lowest percentages of females in the progeny. The functional responses obtained were predominantly type II curves. In all cases considered, no stored energy was allocated for reproduction and, wit h the exception of the wild strain on eggs, the prey was exploited less eff iciently as the consumption increased. In spite of the differences evidence d in this experiment all strains were characterized by high predation and o viposition rates. Thus the results obtained suggest no drawbacks in the use of mass-reared N. californicus as biocontrol agents. Exp Appl Acarol 23: 2 17-234 (C) 1999 Kluwer Academic Publishers.