Prey consumption and functional response of three acarophagous species to eggs of the two-spotted spider mite in the laboratory

Abstract

Comparative investigation of the characteristics related to prey consumption, reproductive rate and searching capacity among predators, which remain largely unexplored, could yield important information for selection of novel control agents. In this paper, the daily prey consumption rate of the immature stages and adult females until 20 days after eclosion of three predators, Stethorus japonicus (lady bug), Scolothrips takahashii (predatory thrips) and Amblyseius californicus (predatory mite), on eggs of Tetranychus urticae (red form) was determined, as well as the functional response of adult females to T. urticae eggs, on lima bean leaf discs in the laboratory at three constant temperatures (18–20, 25 and 30°C) and 16L : 8D. Female and male immatures of S. japonicus consumed the same number of spider-mite eggs, whereas more eggs were eaten by female immatures of S. takahashii and A. californicus than by male immatures at each of the temperatures tested. The total number of eggs consumed during the immature stages did not differ significantly among temperatures for any of the three predators. Consumption of T. urticae eggs by S. japonicus was fastest, followed by S. takahashii. Average daily consumption rates of adult females during the first 20 days after emergence at 25°C were 13.4 eggs for A. californicus, 23.0 eggs for S. takahashii and 294.4 eggs for S. japonicus. Adult females of the three predator species showed a type II functional response to prey density, regardless of the temperatures tested.