ABSTRACT
Arthropods first encounter their chemical environment through a rapid-response, concentration-dependent neurosensory system. Chemical “taste”, or reacting to a stimulus (chemotaxis), is intrinsic to every motile cell or animal and provides the most basic sensory system characteristic of life (Stoddard et al. 1992). It is particularly well developed and diversified among insects where food selection, niche orientation, inter and intra-specific spacing, mating, defense and ultimately a species’ host range are dictated by chemical cues. Insect behaviour, in contrast to a vertebrate, is much more dependent on chemical cues than any other sensory attribute (visual, hearing, touch, etc.), and chemicals more often than physical cues (visual, mechanical) have been identified with successful host plant finding and acceptance (Figure 4.1). Molecular receptors for taste and smell are located on peripheral sensory neurons of antennae, mouth parts, tarsi and the ovipositor. Commitment to feed is primarily determined by the net effects of positive and negative stimuli on these sensory receptors (Dethier 1980; Frazier 1992; Bernays and Chapman 1994; Schoonhoven et al. 1998).
