Chapter 4 SENSORY SYSTEMS AND BEHAVIOR In the opening chapter of this book we suggested that the success of insects derives at least in part from their ability to sense and interpret their surroundings and to discriminate on a fine scale. | TIC04 5 20 04 4 47 PM Page 85 Chapter 4 SENSORY SYSTEMS AND BEHAVIOR Head of a dragonfly showing enormous compound eyes. After Blaney 1976. TIC04 5 20 04 4 47 PM Page 86 86 Sensory systems and behavior In the opening chapter of this book we suggested that the success of insects derives at least in part from their ability to sense and interpret their surroundings and to discriminate on a fine scale. Insects can identify and respond selectively to cues from a heterogeneous environment. They can differentiate between hosts both plant and animal and distinguish among many microclimatic factors such as variations in humidity temperature and air flow. Sensory complexity allows both simple and complex behaviors of insects. For example to control flight the aerial environment must be sensed and appropriate responses made. Because much insect activity is nocturnal orientation and navigation cannot rely solely on the conventional visual cues and in many nightactive species odors and sounds play a major role in communication. The range of sensory information used by insects differs from that of humans. We rely heavily on visual information and although many insects have well-developed vision most insects make greater use of olfaction and hearing than humans do. The insect is isolated from its external surroundings by a relatively inflexible insensitive and impermeable cuticular barrier. The answer to the enigma of how this armored insect can perceive its immediate environment lies in frequent and abundant cuticular modifications that detect external stimuli. Sensory organs sensilla singular sensillum protrude from the cuticle or sometimes lie within or beneath it. Specialized cells detect stimuli that may be categorized as mechanical thermal chemical and visual. Other cells the neurons transmit messages to the central nervous system section where they are integrated. The nervous system instigates and controls appropriate behaviors such as posture movement feeding and .
