Olfactory Cues Are Subordinate to Visual Stimuli in a Neotropical Generalist Weevil

Abstract

The tropical root weevil Diaprepes abbreviatus is a major pest of multiple crops in the Caribbean Islands and has become a serious constraint to citrus production in the United States. Recent work has identified host and conspecific volatiles that mediate host- and mate-finding by D. abbreviatus. The interaction of light, color, and odors has not been studied in this species. The responses of male and female D. abbreviatus to narrow bandwidths of visible light emitted by LEDs offered alone and in combination with olfactory stimuli were studied in a specially-designed multiple choice arena combined with a locomotion compensator. Weevils were more attracted to wavelengths close to green and yellow compared with blue or ultraviolet, but preferred red and darkness over green. Additionally, dim green light was preferred over brighter green. Adult weevils were also attracted to the odor of its citrus host + conspecifics. However, the attractiveness of citrus + conspecific odors disappeared in the presence of a green light. Photic stimulation induced males but not females to increase their speed. In the presence of light emitted by LEDs, turning speed decreased and path straightness increased, indicating that weevils tended to walk less tortuously. Diaprepes abbreviatus showed a hierarchy between chemo- and photo-taxis in the series of experiments presented herein, where the presence of the green light abolished upwind anemotaxis elicited by the pheromone + host plant odor. Insight into the strong responses to visual stimuli of chemically stimulated insects may be provided when the amount of information supplied by vision and olfaction is compared, as the information transmission capacity of compound eyes is estimated to be several orders of magnitude higher compared with the olfactory system. Subordination of olfactory responses by photic stimuli should be considered in the design of strategies aimed at management of such insects.

The importance of olfactory and visual cues in developing better monitoring tools forSirex noctilio(Hymenoptera: Siricidae)

“…Thus, trap efficiency may be improved in the field by the addition of UV light, rather than relying completely on olfactory attractants. The importance of visual cues in monitoring has recently been studied in the tropical root weevil Diaprepes abbreviates L., which showed a hierarchy between chemo‐ and phototaxis, and used visual cues in short‐range host finding (Otalora‐Luna et al , ). A similar pattern of subordination of chemotaxis to phototaxis was shown in many Lepidoptera species (Shorey & Gaston, ; Balkenius et al , ; Goyret et al , ) and in the Colorado potato beetle Leptinotarsa decemlineata (Otalora‐Luna & Dickens, ).…”

Vision-mediated exploitation of a novel host plant by a tephritid fruit fly

“…Predominance of visual over olfactory cues was also reported for Vanessa indica (Lepidoptera: Nymphalidae) by Omura and Honda [37], who found that naive butterflies depended primarily on color and secondarily on scent during flower visitation. In one recent study that evaluated visual responses of the tropical root weevil Diaprepes abbreviatus (Coleoptera: Curculionidae) to light in the presence and absence of citrus volatiles, Otalora-Luna et al [38] documented that, in the absence of light, the addition of citrus volatiles to an air stream during the test period did not elicit an orientation response but the presence of lights elicited a strong weevil response.…”

Navigating on a chemical radar: Usage of root exudates by foragingDiabrotica virgifera virgiferalarvae

“…Plant stimi used by insects as foraging cues are optical and chemical (i.e., volatile organic compounds [VOCs] and contact cues), and are often used in combination of both (Patt & Sétamou, ; Schoonhoven, van Loon, & Dicke, ; Vargas, Troncoso, Tapia, Olivares‐Donoso, & Niemeyer, ). Host odours are regarded as predominant cues initiating insect foraging behaviour and guiding their plant location, particularly in highly specialized insects (Otálora‐Luna, Lapointe, & Dickens, ). However, visual cues are essential for certain herbivorous insects (Stenberg & Ericson, ), and odours sometimes only enhance the insect response to visual cues (Patt & Sétamou, ).…”