The predatory abilities of Amphibolus venator (Klug) on the stored-product insect pest Tribolium confusum Jacquelin du Val were examined. A. venator adults (5-15 days old) were starved for 3 days and then introduced individually into plastic containers containing different prey densities (3, 5, 10, 15 or 20) of last-instar larvae, pupae or adults of T. confusum. The assay was carried out at 25°C and 30°C for 1 day. The number of T. confusum killed by A. venator during 10 days was also investigated a prey density of 10 individuals. A. venator attacked all stages tested: mature larvae, pupae and adults. A. venator targeted mature larvae preferentially to the other stages. The number of prey killed by A. venator increased at high prey density, and the functional response of A. venator exhibited Holling's Type II response for all the prey stages. Females tended to kill more prey than males. Predation by A. venator was more effective at 30°C than at 25°C.

Five species of Chalcididae (Hymenoptera) were collected from rice stores in Thailand. Proconura minusa Narendran was dominant and is thought to be an important parasitoid of Sitotroga cerealella (Olivier). Many individuals of Proconura caryobori (Hanna) were collected, and the host in rice stores of this species was Corcyra cephalonica (Stainton). Antrocephalus mitys (Walker) is known to parasitize C. cephalonica, but few individuals were collected; therefore, it is thought not to be important in Thailand. Notaspidiella clavata Narendran and Konishi sp. nov. and Notaspidium thailandicum Narendran and Konishi sp. nov. are described.

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Abstract:The impact of two predatory bugs, Xylocoris flavipes and Joppeicus paradoxus, on the stored-product insect, Tribolium confusum, was examined. Five pairs of adult T. confusum were placed in a plastic container (dia. 15 cm, height 8 cm) containing 10 g of whole-wheat flour. After 3 d, the following four experimental groups were set up: Control (no predator release), X. flavipes (four pairs of adult X. flavipes released), J. paradoxus (four pairs of adult J. paradoxus released), and X. flavipesϩ J. paradoxus (two pairs each of X. flavipes and J. paradoxus released). Twenty-five days after the release of the predatory insects, we counted the number of living T. confusum, X. flavipes, and J. paradoxus. The number of T. confusum in the X. flavipes-treated and J. paradoxus-treated groups was 3 and 33% of the control, respectively. On the other hand, the suppressive effect of X. flavipesϩJ. paradoxus treatment was lower than that of the above two treatments, probably due to intraguild predation between X. flavipes and J. paradoxus.

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