Oviposition habitat choices of species with aquatic larvae is expected to be influenced by both offspring risk of mortality due to predation, and offspring growth potential. Aquatic predators may indirectly influence growth potential for prey by reducing prey density and, for filter feeding prey, by increasing bacterial food for prey via added organic matter (feces, partially eaten victims), creating the potential for interactive effects on oviposition choices. We tested the hypothesis that the mosquito Aedes aegypti preferentially oviposit in habitats with predatory Toxorhynchites larvae because of indirect effects of predation on chemical cues indicating bacterial abundance. We predicted that A. aegypti would avoid oviposition in sites with Toxorhynchites, but prefer to oviposit where bacterial food for larvae is abundant, and that predation by Toxorhynchites would increase bacterial abundances. Gravid A. aegypti were offered paired oviposition sites representing choices among: predator presence; the act of predation; conspecific density; dead conspecific larvae; and bacterial activity. Aedes aegypti preferentially oviposited in sites with T. theobaldi predation, and with killed conspecific larvae, but failed to detect preferences for other treatments. The antibiotic Tetracycline eliminated the strongest oviposition preference. Both predation by Toxorhynchites and killed larvae increased bacterial abundances, suggesting that oviposition attraction is cued by bacteria. Our results show the potential for indirect effects, like trophic cascades, to influence oviposition choices and community composition in aquatic systems. Our results suggest that predators like Toxorhynchites may be doubly beneficial as biocontrol agents because of the attraction of ovipositing mosquitoes to bacterial by-products of Toxorhynchites feeding.

Haematophagous dipterans of the Nematocera and Brachycera suborders have been objects of study for a better understanding of the behavioral mechanisms used by insects to find their blood meal. This is usually elicited by chemical stimuli (semiochemicals) called kairomones that are often released by the vertebrate hosts (Gibson & Torr 1999).Among the more than 500 species of the subfamily Phlebotominae that are known in the Americas, over 400 belong to the genus Lutzomyia (Young & Duncan 1994, Galati 2003. Lutzomyia longipalpis (Lutz and Neiva) and L. intermedia (Lutz and Neiva) play an important role in the transmission of leishmaniases (Forattini 1973, Lainson 1989, Lemos & Lima 2005. Host-preference studies of Lutzomyia spp. frequently use animals, such as chicken, dogs, horses (Quinnell et al. 1992, Ximenes et al. 1999, Bongiorno et al. 2003, and occasionally humans as bait (Quinnell et al. 1992, Aguiar et al. 1996, Rebollar-Telez et al. 1999, Pinto et al. 2001. Laboratory assays (e.g., precipitin test) have been used for the identification of hosts that provide the blood meal for the phlebotomine sand flies (Christensen et al. 1982, Afonso et al. 2005). CDC light traps (Sudia & Chamberlain 1962) and Shannon traps (Shannon 1939) have been used as tools for monitoring phlebotomine sand flies, thus eliminating the ethical problems associates with using human bait. However, some studies have shown that certain phlebotomine sand fly species are highly anthropophilic but rarely phototropic (Alexander et al. 1995, Travi et al. 1998, while other species seem to be more phototropic than antropophilic, such as Lutzomyia verrucarum Townsend (Davies et al. 1995). It is possible that these species are responsive to non-specific kairomones such as CO 2 (Quinnell et al. 1992, Campbell-Lendrum et al. 1999a, and can be attracted by different species of hosts. CO 2 is the main volatile kairomone released by vertebrates and it is used by most haematophagous insects to find their hosts (Eiras 2001). Knudsen et al. (1979) demonstrated for the first time the attractiveness of CO 2 (released from dry ice) to phlebotomine sand flies. Light traps (LT) baited with CO 2 enhanced the capture of phlebotomine sand flies in the field (Chaniots 1983), despite the fact that attraction to CO 2 was not observed in the laboratory (Nigam & Ward 1991).The chemical 1-octen-3-ol (octenol) is an important kairomone used by zoophilic dipteran species of the families Muscidae, Tabanidae, Ceratopogonidae and Culicidae to seek their hosts (Kline at al. 1990, Gibson & Torr 1999, Bernier et al. 2000, Eiras 2001). To date, there is no evidence supporting the trapping of phlebotomine sand flies with this kairomone. Lactic acid was the first kairomone identified from human skin (Acree et al. 1968), and its effect in attracting mosquitoes has been evaluated, especially in combination with CO 2 (Kline et al. 1990, Eiras & Jepson 1991, ammonia and some fatty acids (Geier et al. 1999). Ammonia was identified from vertebrate odors in the 1970s (Larson et al. 19...

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1. Prey organisms can perceive cues to predation hazard and adopt low‐risk behaviours to increase survival. Animals with complex life cycles, such as insects, can exhibit such anti‐predatory behaviours in multiple life stages.2. Cues to predation risk may induce ovipositing females to choose habitats with low predation risk. Cues to predation risk may also induce larvae to adopt facultative behaviours that reduce risk of predation.3. One hypothesis postulates that anti‐predation behaviours across adult and larval stages may be negatively associated because selection for effective anti‐predator behaviour in one stage leads to reduced selection for avoidance of predators in other stages. An alternative hypothesis suggests that selection by predation favours multi‐component defences, with both avoidance of oviposition and facultative adoption of low‐risk behaviours by larvae.4. Laboratory and field experiments were used to determine whether defensive responses of adult and larval mosquitoes are positively or negatively associated. The study tested effects of waterborne cues from predatory Toxorhynchites theobaldi on oviposition choices and larval behaviours of three of its common prey: Culex mollis, Limatus durhamii and Aedes albopictus.5. Culex mollis shows strong anti‐predator responses in both life stages, consistent with the hypothesis of a multi‐component behavioural defence. The other two species showed no detectable responses to waterborne predator cues in either adult or larval stages. Larvae of these unresponsive species were significantly more vulnerable to this predator than was C. mollis.6. For these mosquitoes, species appear either to have been selected for multi‐component defences against predation or to act in ways that could be called predator‐naïve.

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RESUMO Para avaliar o papel do octenol na coleta de anofelinos foram utilizadas armadilhas

) foram registradas pela primeira vez, aumentando a diversidade da fauna de fl ebotomíneos do município para 23 espécies. As espécies relatadas como primeiros registros e sua distribuição são citadas e discutidas.

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