PERSPECTIVES AND OVERVIEWLocation and selection of an oviposition site is an essential part of the life history of all mosquito species. The remarkable number of oviposition be haviors range from the common, e.g. deposition of eggs on or near the water surface, to the unusual, e.g. egg brooding by adult females (73,74). The initiation of an ovipositional flight is linked with environmental factors, especially rainfall, relative humidity, temperature, and wind speed. The location and selection of an oviposition site involves visual, olfactory, and tactile responses.Since pathogen acquisition by vector mosquitoes usually requires the taking of at least one blood meal, disease transmission usually requires the comple tion of at least one oviposition cycle before pathogen transfer can occur with a subsequent blood meal. Oviposition is thus an important component of most mosquito-borne diseases.A tremendous amount has been written concerning mosquito oviposition. A large proportion of the studies have dealt with laboratory investigations on mosquito response to chemical and physical aspects of the oviposition site;relatively few field studies have been attempted. In this review we discuss general aspects of mosquito oviposition in nature, as well as the interplay 401 0066-4170/89/0101-0401$02.00 Annu. Rev. Entomol. 1989.34:401-421. Downloaded from arjournals.annualreviews.org by Yale University STERLING CHEMISTRY LIBRARY on 10/11/09. For personal use only. Quick links to online content Further ANNUAL REVIEWS 402 BENTLEY & DAY of chemical, physical, and physiological factors in oviposition site selection.Considering the number of published papers in the literature on oviposition, it is not possible for us to cite all of the important work. Rather, we attempt a broad survey of selected aspects of the chemical ecology and the oviposition behavior of gravid mosquitoes. OVIPOSITION BEHA VIOR IN NATUREThere are many similarities between mosquito host-seeking and oviposition behaviors. Both require complex integration of physical and chemical cues by searching mosquitoes. Long-range cues, probably involving vision, allow mosquitoes to identify different habitats (14) and specific host and oviposition site characteristics. As mosquitoes approach a host or an oviposition site other cues become important. For example, olfactory cues help mosquitoes to identify CO2 odor plumes from a host or volatile factors at the oviposition site. Once a host or an oviposition site has been identified, short-range cues become increasingly important. Short-range cues include temperature and chemical signals received by contact chemoreceptors. E1ectrophysiological studies have demonstrated that as the blood meal is digested in Aedes aegypti, neurons sensitive to host-produced cues, such as lactic acid, become less sensitive, while neurons sensitive to oviposition site attractants, such as methyl butyrate, become more sensitive (25).Certain mosquito species exhibit a great deal of specialization in both host and oviposition site selection, while ...

The burden of gene transfer from one mosquito generation to the next falls on the female and her eggs. The selection of an oviposition site that guarantees egg and larval survival is a critical step in the reproductive process. The dangers associated with ephemeral aquatic habitats, lengthy droughts, freezing winters, and the absence of larval nutrition makes careful oviposition site selection by a female mosquito extremely important. Mosquito species exhibit a remarkable diversity of oviposition behaviors that ensure eggs are deposited into microenvironments conducive for successful larval development and the emergence of the next mosquito generation. An understanding of mosquito oviposition behavior is necessary for the development of surveillance and control opportunities directed against specific disease vectors. For example, Aedes aegypti Linnaeus is the vector of viruses causing important human diseases including yellow fever, dengue, chikungunya, and Zika. The preference of this species to oviposit in natural and artificial containers has facilitated the development of Ae. aegypti-specific surveillance and toxic oviposition traps designed to detect and control this important vector species in and around disease foci. A better understanding of the wide diversity of mosquito oviposition behavior will allow the development of new and innovative surveillance and control devices directed against other important mosquito vectors of human and animal disease.

The optical, fluorescent, and photoconductive properties of solution-processable functionalized pentacene and anthradithiophene (ADT) derivatives are presented. Considerable fluorescence quantum yields of ∼70-75% and ∼40-50% were observed in several ADT derivatives in toluene solutions and in thin films, respectively. No electric field-induced fluorescence quenching was observed in films at applied electric fields of up to at least 2 × 10 5 V/cm. Strong temperature dependence of fluorescence quantum yields was observed in all ADT films but not solutions, which emphasizes importance of intermolecular interactions in these materials. All films exhibited fast charge carrier photogeneration upon 100 fs 400 nm excitation and power-law decay dynamics of the transient photocurrent over many orders of magnitude in time. In solution-deposited ADT thin films, effective charge carrier mobilities calculated from the space-charge-limited currents reached ∼0.1 cm 2 /V • s. In the same films, bulk photoconductive gains of up to 130 were observed at 532 nm continuous wave excitation with light intensity of 0.58 mW/cm 2 at the applied electric field of 4 × 10 4 V/cm.

We used a dynamic hydrology model to simulate water table depth (WTD) and quantify the relationship between Saint Louis encephalitis virus (SLEV) transmission and hydrologic conditions in Indian River County, Florida, from 1986 through 1991, a period with an SLEV epidemic. Virus transmission followed periods of modeled drought (specifically low WTDs 12 to 17 weeks before virus transmission, followed by a rising of the water table 1 to 2 weeks before virus transmission). Further evidence from collections of Culex nigripalpus (the major mosquito vector of SLEV in Florida) suggests that during extended spring droughts vector mosquitoes and nestling, juvenile, and adult wild birds congregate in selected refuges, facilitating epizootic amplification of SLEV. When the drought ends and habitat availability increases, the SLEV-infected Cx. nigripalpus and wild birds disperse, initiating an SLEV transmission cycle. These findings demonstrate a mechanism by which drought facilitates the amplification of SLEV and its subsequent transmission to humans.

St. Louis encephalitis virus was first identified as the cause of human disease in North America after a large urban epidemic in St. Louis, Missouri, during the summer of 1933. Since then, numerous outbreaks of St. Louis encephalitis have occurred throughout the continent. In south Florida, a 1990 epidemic lasted from August 1990 through January 1991 and resulted in 226 clinical cases and 11 deaths in 28 counties. This epidemic severely disrupted normal activities throughout the southern half of the state for 5 months and adversely impacted tourism in the affected region. The accurate forecasting of mosquito-borne arboviral epidemics will help minimize their impact on urban and rural population centers. Epidemic predictability would help focus control efforts and public education about epidemic risks, transmission patterns, and elements of personal protection that reduce the probability of arboviral infection. Research associated with arboviral outbreaks has provided an understanding of the strengths and weaknesses associated with epidemic prediction. The purpose of this paper is to review lessons from past arboviral epidemics and determine how these observations might aid our ability to predict and respond to future outbreaks.

We show that the spatial-temporal variability of human West Nile (WN) cases and the transmission of West Nile virus (WNV) to sentinel chickens are associated with the spatial-temporal variability of drought and wetting in southern Florida. Land surface wetness conditions at 52 sites in 31 counties in southern Florida for 2001-2003 were simulated and compared with the occurrence of human WN cases and the transmission of WNV to sentinel chickens within these counties. Both WNV transmission to sentinel chickens and the occurrence of human WN cases were associated with drought 2-6 mo prior and land surface wetting 0.5-1.5 mo prior. These dynamics are similar to the amplification and transmission patterns found in southern Florida for the closely related St. Louis encephalitis virus. Drought brings avian hosts and vector mosquitoes into close contact and facilitates the epizootic cycling and amplification of the arboviruses within these populations. Southern Florida has not recorded a severe, widespread drought since the introduction of WNV into the state in 2001. Our results indicate that widespread drought in the spring followed by wetting during summer greatly increase the probability of a WNV epidemic in southern Florida.

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We present a detailed study, on time scales from picoseconds to seconds, of transient and continuous wave (cw) photoconductivity in solution-grown thin films of functionalized pentacene (Pc), anthradithiophene (ADT), and dicyanomethylenedihydrofuran (DCDHF). In all films, at temperatures of 285–350 K, we observe fast carrier photogeneration and nonthermally activated charge transport on picosecond time scales. At ∼30 ps after photoexcitation at room temperature and at applied electric field of 1.2×104 V/cm, values obtained for the product of mobility and photogeneration efficiency, μη, in ADT-tri-isoproplysilylethynyl-(TIPS)-F, Pc-TIPS, and DCDHF films are ∼0.018–0.025, ∼0.01–0.022, and ∼0.002–0.004 cm2/V s, respectively, depending on the film quality, and are weakly electric field dependent. In functionalized ADT and Pc films, the power-law decay dynamics of the transient photoconductivity is observed, on time scales of up to ∼1 μs after photoexcitation, in the best samples. In contrast, in DCDHF amorphous glass, most of the photogenerated carriers are trapped within ∼200 ps. Transport of photoexcited carriers on longer time scales is probed by cw illumination through an optical chopper, with a variable chopper frequency. In contrast with what is observed on picosecond time scales, charge carriers on millisecond and longer time scales are predominantly localized, and are characterized by a broad distribution of carrier lifetimes. Such carriers make the principal contributions to dc photoconductivity.