Attraction and oviposition preferences of Phlebotomus papatasi (Diptera: Psychodidae), vector of Old-World XXXX , to larval rearing media.

@entity4536 @entity95 @entity238
BACKGROUND: As part of a project aimed at developing oviposition attractants for the control and surveillance of Phlebotomus papatasi (a vector of Old-World @entity4536 ), we tested the hypothesis that gravid sand flies are attracted to chemical cues emanating from the growth medium of conspecific larvae - predominantly larvae-conditioned host feces that represents a suitable oviposition site. We report the results of a systematic assessment of media from various developmental stages of the sand @entity238 using oviposition and olfactometer behavioral assays. METHODS: We conducted multiple-choice oviposition assays in 500  mL Nalgene jars. Six treatments were placed on separate filter paper discs at the bottom of the jar: 2(nd)/3(rd) larval instar medium, 4(th) larval instar/pupae medium, frass from expired colonies, larval food (aged @entity95 chow and @entity95 feces mix), @entity95 feces, and a solvent (water) control. Fifty gravid females were introduced into each jar. Cumulative number of eggs laid on each filter paper per jar was counted at different time intervals from digital images. Attraction of gravid sand flies to these six treatments was assayed with a 3-chamber linear olfactometer. Twenty gravid females were transferred to the middle chamber of the olfactometer and their distribution in treatment and control chambers was recorded after 3  h. RESULTS: Almost no eggs were oviposited during the first 72  h following a blood-meal. Cumulative egg deposition increased drastically in the next 24  h (hours 73-96), with a slight non-significant increasing trend thereafter. Comparing mean cumulative egg deposition among the six treatments, we found that significantly more eggs were oviposited on 2(nd)/3(rd) larval rearing medium followed by 4(th) instar/pupae rearing medium. Oviposition preference did not vary over time. The olfactometer results were consistent with the oviposition assays, with 2(nd)/3(rd) larval rearing medium being the most attractive, followed by 4(th) instar/pupae rearing medium. CONCLUSION: The key finding of this study is that gravid, laboratory reared, Ph. papatasi sand flies are significantly more attracted to rearing medium of the most biologically active larval stages (2(nd)/3(rd) instar and 4(th) instar/pupae). This finding indicates that sand @entity238 -digested host food and feces is attractive to gravid females and suggests that the larvae and larval gut microbiome may be involved in conditioning the oviposition substrate and possibly the production of oviposition attractants and stimulants.
