SOME ASPECTS OF THE BIOLOGY AND A LABORATORY LIFE TABLE OF THE ACARINE PREDATOR <i>ZETZELLIA MALI</i>

Abstract

Abstract A rearing technique was developed to study various aspects of the biology of Zetzellia mali (Ewing) in the laboratory. The rate of development of Z . mali feeding upon the phytophagous mite Aculus schlechtendali (Nalepa) was determined at 9°±1°C and 14°±1°C (56% R.H.), 19°±1°C (33%, 56%, 76%, and 97% R.H.), and 24°±1°C (51% R.H.). The average preovipositional and ovipositional periods for 16 female Z . mali were 1.5 and 9.4 days respectively and an average of 1.7 eggs per day were laid by these females. Z . mali was found to be arrhenotokous with unmated females producing only male offspring and mated females producing 2.6 females: 1 male offspring. Diapause in Z . mali was broken at 24°±1°C, 16L:8D) with egg deposition beginning after 11 days (51% and 76% R.H.) or 12 days (33% and 96% R.H.) when the adults feed upon the winter eggs of Panonychus ulmi (Koch). A life table was constructed for Z . mali and the intrinsic rate of increase (r m ) was determined to be 0.109 female offspring/female/day. The mean generation time (T) was calculated to be 21.0 days and the net reproductive rate (R 0 ) during this time was 10.04. The theoretical stable age distribution of the laboratory population of Z . mali at 19°±1°C, 56% R.H. was 59% eggs, 15% larvae, 7% protonymphs, 6% deutonymphs, and 13% adults. Comparison of the intrinsic rates of increase and prey consumption of Z . mali and other species of predaceous mites indicate that Z . mali is not as efficient a regulating agent of phytophagous mites as the phytoseiids.