Abstract
The effects of host and parasitoid density on rates of parasitism by Trichogramma minutum, T. pretiosum , and T. exiguum were tested in l.8-liter (13 cm diam by 13 cm high), 43-liter (23 by 36 by 52 cm), and 4,000-liter (2 by 2 by 1 m) arenas. Soybean foliage and Heliothis virescens eggs served as substrate and hosts, respectively. Rates of parasitism were significantly higher at the highest wasp density in all arenas. The effects of host density were not consistent among arenas. Rates of parasitism by T. minutum were the highest in the l.8-liter and the lowest in the 4,000-liter arenas. Rates of parasitism by T. pretiosum exhibited the opposite trend. Rates of parasitism by T. exiguum did not differ significantly from those of T. minutum in the l.8-liter arena and T. pretiosum in the 4,000-liter arena. The cause of this lack of congruence in the relative performance of T. minutum and T. pretiosum in the different sized arenas was not determined, however it may be a result of differential vertical stratification of searching activity by these two species.
Published Version
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