Rhynchophorus ferrugineus: Behavior, Ecology, and Communication

Red palm weevil (RPW) ecology is characterized by the adults' ability to aggregate on palms. The aggregation process has the functions of protection, feeding, and reproduction for the individuals. Semiochemicals and visual cues strongly influence this behavior at intraspecific and interspecific levels. Adults actively fly over long distances, following chemical cues, such as aggregation pheromone and host plant odor, or visual cues to colonize a new host. The aggregation pheromone of RPW is a male-produced mixture of 4-methyl-5-nonanol (major component) and the related ketone 4-methyl-5-nonanone (minor component). These compounds are largely used in the field to lure males and especially females to traps. Visual cues also play a role, as color vision in RPW is tuned to the detection and recognition of conspecifics and to the contrast created by vegetation on the sky's UV-rich background. The role of host plant odor, the so-called kairomone, in host plant-finding behavior has been evidenced in field studies. Ethyl acetate and ethyl alcohol, abundant in the odor emitted by wounded or infested palms and by other fermenting plant material, contribute to the attraction. It is likely that the RPW use particular mixtures of compounds rather than a "palm-specific" one to orient and recognize the host. In this process, visual cues are also likely to play a role, as it has been inferred that the RPW has well-developed color vision and may be attracted by the dark holes in the palm trunk for oviposition, or the red color of its cuticle. This chapter describes the RPW's intra- and interspecific behaviors. Flight capability and chemical and visual cues that influence mating, aggregation, and host finding are outlined.