Host Odor Perception in Phytophagous Insects

Abstract

Phytophagous insects show specialized feeding habits. In general, each species feeds on a restricted range of taxonomically related plant species and in addition limits its feeding to particular plant parts. Most studies on insect-plant rela­ tionships concern pest species in agricultural systems, which do not show the stability of the insect's original ecosystem. In monocultures host plants of high quality are present over large areas. Despite the biased nature of these in­ teractions, some generations of insects are forced to disperse and must find new host plants on which feeding results in growth and reproduction. (182). Host selection in phytophagous insects consists of a sequence of behavioral re­ sponses to an array of stimuli associated with host and nonhost plants. The insects are equipped with sensory receptors enabling them to perceive these stimuli. Plant stimuli involved include in varying proportions visual, mechani­ cal, gustatory, and olfactory characteristics (158). Plant odors have been considered of minor importance in host selection for many insect species, especially those that perform as r-strategists (93). This view needs to be reconsidered because such insects as aphids (21, 121, 122), whiteflies (173), and rice brown planthoppers (117), possess the full equipment of olfactory receptors and are attracted by host plant odors. In the present review selection was made mainly from the literature of the last 20 years. Floral relationships and social insects were excluded. Readers are invited to consult related reviews (49, 145, 158) as well as Dethier (27) for older Iiterature .