Attraction of Conspecific Insects

Insects also can signal the presence of suitable resources to conspecific insects. Such cooperation increases opportunities for acquisition of shared resources or larger prey and improves mating success (see Chapter 4).

Acoustic signals (stridulation) from potential mates, especially if combined with attractive host cues, advertise discovery and evaluation of suitable resources. Stridulation contributes to optimal spacing and resource exploitation by colonizing bark beetles (Raffa et al. 1993, Rudinsky and Ryker 1976).

Attractive and repellent chemicals produced by insects (pheromones) also advertise the location of suitable resources and potential mates (Fry and Wehner 2002, Raffa et al. 1993, Rudinsky and Ryker 1976). Most insects produce pheromones, but those of Lepidoptera, bark beetles, and social insects have been studied most widely. Social insects produce recognition pheromones that distinguish colony members from noncolony members and trail pheromones that are deposited along foraging trails to guide other members of a colony to food resources and back to the colony (B. Smith and Breed 1995,Traniello and Robson 1995). Trail pheromones also are used by tent caterpillars (Fitzgerald 1995).

A variety of chemical structures are used to mark trails (Fig. 3.14). A plant-derived monoterpene, geraniol, is obtained from flower scents, concentrated, and used by honey bees, Apis mellifera, to mark trails and floral resources (Harborne 1994). Trail markers can be highly effective. The trail marker produced by the leaf-cutting ant, Atta texana, is detectable by ants at concentrations of 3.48 x 108 molecules cm-1, indicating that 0.33 mg of the pheromone would be sufficient to mark a detectable trail around the world (Harborne 1994). Although trail markers were once thought to be species specific, more recent work has shown that multiple species may use the same compounds as trail markers, with varying degrees of interspecific recognition (Traniello and Robson 1995). Furthermore, synthetic analogues (e.g., 2-phenoxyethanol) also may elicit trail-following behavior, despite little structural similarity to natural trail markers (J. Chen et al. 1988).

Von Frisch (1967) pioneered study of the sophisticated communication used by honey bees. The elaborate movements of the "bee dance" communicate distance and direction to suitable resources to other foragers (F. Dyer 2002).

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