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Bromeliads as Ovipositional Sites for Wyeomyia Mosquitoes: Form and Color Influence Behavior
J. H. Frank
The Florida Entomologist
Vol. 69, No. 4 (Dec., 1986), pp. 728-742
Published by: Florida Entomological Society
Stable URL: http://www.jstor.org/stable/3495221
Page Count: 15
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Bromeliad models in cages containing adult Wyeomyia vanduzeei or W. mitchellii (Diptera: Culicidae) allowed quantification of ovipositional response to paired contrasts of form, color, or contained fluid of the models. In 13 of 15 contrasts, mosquitoes of both species showed the same direction of preference, but in each of these 13 contrasts W. mitchellii showed an equal or stronger response. If strength of response indicates degree of specialization, then W. mitchellii is visually more of a bromeliad-specialist. In 2 contrasts, W. vanduzeei showed a greater preference for lighter, less saturated yellowish green (and for green), and W. mitchellii showed a greater preference for a darker, more saturated yellowish green (and for yellow). These preferences may be related to level of shade of the habitat occupied by each species. Model bromeliads showing distinct leaflike form were greatly preferred by both species to models lacking such form, and visual perception of fluid in the cup of the model greatly increased its acceptability as an oviposition site. A simulated bromeliad flower spike increased ovipositional response to the model, which was unexpected because previous work had shown reduced oviposition in real bromeliads with flower spikes. It remains unclear if or how the mosquitoes responded to the chemical odor of leaves of the bromeliad Tillandsia utriculata. The mosquitoes Wyeomyia vanduzeei Dyar & Knab and W. mitchellii (Theobald), and possibly all members of this genus, fly and oviposit during daylight hours (Frank et al. 1985). Conceivably this behavior might allow them to respond to finer visual cues than available to the majority of nocturnal mosquitoes. Certainly their responses to colors differ radically from those of more typical mosquitoes, for they prefer light-colored oviposition sites whereas more typical mosquitoes prefer dark-colored sites (Frank 1985). Their eggs are laid singly in brief, hovering ovipositional flights. Their preference for light-colored oviposition sites and their daylight ovipositional flights relate to the development of their preimoginal stages in water held in leaf axils of bromeliads. Leaves of most bromeliads, viewed in daylight, are of light color. In fact, most bromeliad leaves are yellowish green, showing greater or lesser amounts of lightness and saturation. Bromeliads also grow and show a range of size, and they vary interspecifically and intergenerically in size, shape, and chemical characteristics. The question of which of these plant properties are recognized by the mosquitoes, and which serve as cues to signal the suitability of oviposition sites was examined preliminarily by Frank et al. (1976), and Frank & Curtis (1982), but many questions were not readily amenable to experimentation until the development of a model bromeliad (Frank 1985). This model was accepted as an oviposition site by mosquitoes of both species and could be altered in form, color, and fluid content to isolate characteristics of possible consequence to the mosquitoes. Detection of bromeliads by W. vanduzeei and W. mitchellii is quite comparable to herbivorous insect host selection, a subject reviewed ably by Prokopy & Owens (1983). Another mosquito attracted to plants as oviposition sites is Wyeomyia smithii (Coquillett) which oviposits in pitchers of the carnivorous plant Sarracenia purpurea L. and whose attraction to simulated pitchers was reported by Istock et al. (1983). The work reported below was designed to identify characteristics of bromeliads of consequence to ovipositing W. vanduzeei and W. mitchellii. It offered the special advantage that both of these related mosquitoes could be investigated simultaneously by identical methods, allowing direct comparison of their responses.
The Florida Entomologist © 1986 Florida Entomological Society