Introduction: predators, parasites, parasitoids; the challenge of host selection. Ambush: classic examples; mimicry; detection. Trapping: classic examples; how traps work; detection and attack. Hunting: classic examples; vision, odours and sound. Searching: search strategies; examples; modalities; effective space. Sources of host selection cues: role of plants; the host; associated organisms. Plants and host selection: role of plants in attracting parasitoids and predators; source and chemistry of synamones. Host detection: cairomones; shape; movement. Chemical cues: long and short range cues; chemistry of synamones and cairomones. Vision and vibrational cues: receptors. Genetics and learning: plasticity of host selection. The final decision: egg deposition; novel and artificial hosts; external and internal factors. The next generation: host marking; effect of entomophages on host behaviour and physiology; parasites and their effect on the host. Host defenses: how prey or host tries to escape.