Intraspecific variation of reproductive characteristics of Amblyseius californicus (McGregor) (Acari: Phytoseiidae)

Reproductive characteristics of a commercial strain of Amblyseius caliornicus were compared with those of populations native to Japan to estimate their ability to control spider mites in crop fields. Reproductive characteristics differed among strains. Tire commercial strain showed unique characteristics among the strains examined: short developmental period, high daily fecundity, and long post-oviposition period. Consequently, the intrinsic rate of natural increase (gamma m) of the commercial strain was highest among strains. The commercial strain grew faster than did native populations. Thereby, it could control spider mites. On the other hand, high performance of reproduction showed the potential to displace genetically native populations in crop fields and natural vegetation. This study showed that the long post-oviposition period in the commercial strain is the only character that could lead to displacement or competitive exclusion.