Variations of foraging tactics in a water bug,Diplonychus indicus

The predatory behaviour ofDiplonychus indicus Venk. & Rao (Heteroptera: Belostomatidae), a tropical water bug, appeared to be highly versatile. Male adultD. indicus alternated from active foraging to ambushing during the same observation. The predatory movements described here were divided into 7 different categories. Five include ambushing and no active search: simple capture, strike, lunge and strikes following a preliminary vertical or horizontal orientation. Two include active search: dive and swimming bout. Success rates of capture varied with predatory movement category and with predatorprey distance. Attempts including lunges had the highest success rate. Attempts including short lunges, small vertical or horizontal turns or short dives were less likely to be successful than attempts including relatively longer lunges, larger vertical or horizontal turns or longer dives.