Production Of Adult Mosquitoes Research Articles

Spatial aggregation of aquatic habitats affects oviposition patterns in Aedes mosquitoes.

Colonization, including oviposition, is an important driver of population and community dynamics both within and across habitat patches. Most research has focused on the roles of habitat availability or quality on colonization and its outcomes. However, the spatial distribution of habitats also likely affects these processes. We conducted field experiments in Georgia, USA, using clustered and dispersed arrays of equal numbers of oviposition patches to investigate how patch aggregation influenced oviposition by Aedes mosquitoes. We tested the effects of aggregation on: (1) the total number of eggs an array received, (2) the proportion of patches within an array that received eggs, and (3) the number of eggs per colonized patch. We compared results to predictions from three models (Field of Dreams, Propagule Redirection, and Excess Attraction), which vary in the degree to which arrays attract colonists and apportion those colonists among patches. Clustered arrays received 22% more eggs than dispersed arrays, with clustered patches significantly more likely to receive eggs. At the species level, A. albopictus responded more to clustering than did A. triseriatus. These results are inconsistent with Propagule Redirection, but support the Excess Attraction and Field of Dreams models. Although clustered arrays occupied a relatively small area, they attracted at least as many ovipositing mosquitoes as did dispersed arrays. However, the number of eggs per colonized patch did not differ between clustered and dispersed arrays. Therefore, density dependence among larvae, and hence the production of adult mosquitoes on a per-patch basis, should be similar in dispersed and clustered landscapes.

How can mortality increase population size? A test of two mechanistic hypotheses.

Overcompensation occurs when added mortality increases survival to the next life-cycle stage. Overcompensation can contribute to the Hydra effect, wherein added mortality increases equilibrium population size. One hypothesis for overcompensation is that added mortality eases density dependence, increasing survival to adulthood ("temporal separation of mortality and density dependence"). Mortality early in the life cycle is therefore predicted to cause overcompensation, whereas mortality later in the life cycle is not. Another hypothesis for overcompensation is that threat of mortality (e.g., from predation) causes behavioral changes that reduce overexploitation of resources, allowing resource recovery, and increasing production of adults ("prudent resource exploitation"). Behaviorally active predation cues alone are therefore predicted to cause overcompensation. We tested these predictions in two experiments with larvae of two species of Aedes. As predicted, early mortality yielded greater production of adults, and of adult females, and greater estimated rate of population increase than did later mortality. Addition of water-borne predation cues usually reduced browsing on surfaces in late-stage larvae, but contrary to prediction, resulted in neither significantly greater production of adult mosquitoes nor significantly greater estimated rate of increase. Thus we have strong evidence that timing of mortality contributes to overcompensation and the Hydra effect in mosquitoes. Evidence that predation cues alone can result in overcompensation via prudent resource exploitation is lacking. We expect the overcompensation in response to early mortality will be common in organisms with complex life cycles, density dependence among juveniles, and developmental control of populations.

Water source most suitable for rearing a sensitive malaria vector, Anopheles funestus in the laboratory.

Background: Theinsecticide susceptibility status of Anopheles funestus, one of the main malaria vectors inthe Afrotropicalregions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their larvae in natural breeding sites, rearing and maintaining them in normal laboratory conditions have been a difficult task. Forced-egg laying technique has been a very good tool to generate eggs from adult mosquitoes collected from the wild but rearing these eggs to obtain satisfying portion as adults has always been the problem. In this study, we optimized the development of mosquito species larvae under standard laboratory conditions for desired production of adult mosquitoes that can be useful for insecticide susceptibility tests. Methods: A forced-egg laying technique was used to obtain eggs from gravid female Anopheles funestus collected from Kpome locality in Benin. Eggs were reared in three different water samples (water from the borehole,and two mineral water namely FIFA and Possotômè) and larvae were fed with TetraMin baby fish food. The physico-chemical parameters of the waters were investigated prior to use for egg incubation. Results:In contrast to mineral water that had no contamination, the borehole water source was contaminated with lead (2.5mg/L) and nitrate (118.8mg/L). Egg hatching rates ranged as 91.9 ± 4.4%, 89.1 ± 2.5% and 87.9 ± 2.6% in FIFA, Possotômè and borehole water respectively. High emergence of larvae to adult mosquitoes was recorded as in FIFA (74.3%) and Possotômè(79.5%) water. No adult mosquito was obtained from larvae reared in borehole water. Conclusions: This study gave insight on the water sources that could be good for rearing to mass produce An. funestus in the laboratory. More analysis with other local mineral water sources in our environments could be considered in the future, hopefully giving better outputs.

Water source most suitable for rearing a sensitive malaria vector, Anopheles funestus in the laboratory

Background: The insecticide susceptibility status of Anopheles funestus, one of the main malaria vectors in the Afrotropical regions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their larvae in natural breeding sites, rearing and maintaining them in normal laboratory conditions have been a difficult task. Forced-egg laying technique has been a very good tool to generate eggs from adult mosquitoes collected from the wild but rearing these eggs to obtain satisfying portion as adults has always been the problem. In this study, we optimized the development of mosquito species larvae under standard laboratory conditions for desired production of adult mosquitoes that can be useful for insecticide susceptibility tests. Methods: A forced-egg laying technique was used to obtain eggs from gravid female Anopheles funestus collected from Kpome locality in Benin. Eggs were reared in three different water samples (water from the borehole, and two mineral water namely FIFA and Possotômè) and larvae were fed with TetraMin baby fish food. The physico-chemical parameters of the waters were investigated prior to use for egg incubation (introduction of eggs’ batches into water). Results: In contrast to mineral water that had no contamination, the borehole water source was contaminated with lead (2.5mg/L) and nitrate (118.8mg/L). Egg hatching rates ranged as 91.9 ± 4.4%, 89.1 ± 2.5% and 87.9 ± 2.6% in FIFA, Possotômè and borehole water respectively. High emergence of larvae to adult mosquitoes was recorded as in FIFA (74.3%) and Possotômè (79.5%) water. No adult mosquito was obtained from larvae reared in borehole water. Conclusions: This study gave insight on the water sources that could be good for rearing to mass produce An. funestus in the laboratory. More analysis with other local mineral water sources in our environments could be considered in the future, hopefully giving better outputs.

Water source most suitable for rearing a sensitive malaria vector, Anopheles funestus in the laboratory

Background: The insecticide susceptibility status ofAnopheles funestus,one of the main malaria vectors in the Afrotropical regions, remains under-studied due to the difficulty of working with this mosquito species. Collecting their larvae in natural breeding sites, rearing and maintaining them in normal laboratory conditions have been a difficult task. Forced-egg laying technique has been a very good tool to generate eggs from adult mosquitoes collected from the wild but rearing these eggs to obtain satisfying portion as adults has always been the problem. In this study, we optimized the development of mosquito species larvae under standard laboratory conditions for desired production of adult mosquitoes that can be useful for insecticide susceptibility tests.Methods: A forced-egg laying technique was used to obtain eggs from gravid femaleAnopheles funestuscollected from Kpome locality in Benin. Eggs were reared in three different water samples (water from the borehole,and two mineral water namely FIFA and Possotômè) and larvae were fed with TetraMin baby fish food. The physico-chemical parameters of the waters were investigated prior to use for egg incubation.Results:In contrast to mineral water that had no contamination, the borehole water source was contaminated with lead (2.5mg/L) and nitrate (118.8mg/L). Egg hatching rates ranged as 91.9 ± 4.4%, 89.1 ± 2.5% and 87.9 ± 2.6% in FIFA, Possotômè and borehole water respectively. High emergence of larvae to adult mosquitoes was recorded as in FIFA (74.3%) and Possotômè(79.5%) water. No adult mosquito was obtained from larvae reared in borehole water.Conclusions:This study gave insight on the water sources that could be good for rearing to mass produceAn. funestusin the laboratory. More analysis with other local mineral water sources in our environments could be considered in the future, hopefully giving better outputs.

Integrated Mosquito Management in Experimental Constructed Wetlands: Efficacy of Small-Stature Macrophytes and Fluctuating Hydroperiod

The impact of small-stature alkali bulrush (Bolboschoenus maritimus) and two hydroperiod treatments (early season raised water level or ambient water level) on mosquito production and water quality was studied in replicate 0.09 ha free water surface (FWS) treatment wetlands. Following reconfiguration of a 1-ha constructed wetland into a system with six replicate wetlands, bulrush was planted on 0.5-m centers in three 5-m wide bands in each wetland in summer, 2012. Open water and the low density of emergent vegetation effectively limited mosquito production from the bands of B. maritimus in each wetland during summer and autumn of year one. After the autumnal senescence of the bulrush culms, water levels were raised in half of the wetlands during winter and early spring to enhance sinking of dead bulrush biomass to reduce harborage for mosquitoes. Macrophyte coverage continued to increase in both hydroperiod treatments during year two, but non-bulrush species proliferated and eventually overgrew B. maritimus. Immature mosquito abundance in dipper samples from wetlands in the raised water level treatment was greater than from wetlands in the constant water level treatment. During spring of year two, adult mosquito production was associated with volunteer vegetation in the center of the test cells and averaged 6–18 mosquitoes m−2·day−1, approximately twice that of the other treatment. Hydrological regime did not significantly affect water quality performance (removal of nitrogen, phosphorus and chemical oxygen demand) in the wetlands. Alkali bulrush can persist in shallow water (depth < 0.2 m), but did not persist in deeper zones (mean depth > 0.4 m) of the wetlands and after comparatively large stature grasses and cattails colonized the wetlands. Raised planting beds interspersed with zones of deeper water are recommended to facilitate persistence of alkali bulrush and to limit proliferation of superior competitors.

Bioinsecticide and leaf litter combination increases oviposition and reduces adult recruitment to create an effective ovitrap for Culex mosquitoes.

Mosquito egg traps, aquatic habitats baited with oviposition attractant and insecticide, are important tools for surveillance and control efforts in integrated vector management programs. The bioinsecticide Bacillus thuringiensis subsp. israelensis (Bti) is increasingly used as an environmentally friendly alternative to chemical insecticides and the combination of Bti with a simple oviposition attractant like leaf litter to create an effective egg trap seems appealing. However, previous research suggests that Bti may itself alter oviposition, and that leaf litter may dramatically reduce Bti toxicity. Here we present results from field experiment designed to link the effects of litter and Bti on mosquito oviposition habitat selection and post-colonization survival to production of adult mosquitoes. Tripling litter increased Culex spp. oviposition nearly nine-fold, while Bti had no effect on oviposition. Neither factor altered egg survival, thus larval abundance reflected the effects of litter on oviposition. Both Bti and litter reduced larval survival by ∼60%. We found no evidence that increased litter reduced Bti toxicity. Adult production was dependent upon both litter and Bti. In the absence of Bti, effects of litter on oviposition translated into three-fold more adults. However, in the presence of Bti, initial increases in oviposition were erased by the combined negative effects of Bti and litter on post-colonization survival. Thus, our study provides field evidence that combined litter and Bti application creates an effective ovitrap. This combined treatment had the highest oviposition and the lowest survival, and thus removed the greatest number of mosquitoes from the landscape.

Mosquito Population Regulation and Larval Source Management in Heterogeneous Environments

An important question for mosquito population dynamics, mosquito-borne pathogen transmission and vector control is how mosquito populations are regulated. Here we develop simple models with heterogeneity in egg laying patterns and in the responses of larval populations to crowding in aquatic habitats. We use the models to evaluate how such heterogeneity affects mosquito population regulation and the effects of larval source management (LSM). We revisit the notion of a carrying capacity and show how heterogeneity changes our understanding of density dependence and the outcome of LSM. Crowding in and productivity of aquatic habitats is highly uneven unless egg-laying distributions are fine-tuned to match the distribution of habitats’ carrying capacities. LSM reduces mosquito population density linearly with coverage if adult mosquitoes avoid laying eggs in treated habitats, but quadratically if eggs are laid in treated habitats and the effort is therefore wasted (i.e., treating 50% of habitat reduces mosquito density by approximately 75%). Unsurprisingly, targeting (i.e. treating a subset of the most productive pools) gives much larger reductions for similar coverage, but with poor targeting, increasing coverage could increase adult mosquito population densities if eggs are laid in higher capacity habitats. Our analysis suggests that, in some contexts, LSM models that accounts for heterogeneity in production of adult mosquitoes provide theoretical support for pursuing mosquito-borne disease prevention through strategic and repeated application of modern larvicides.

Influence of Leaf Detritus Type on Production and Longevity of Container-Breeding Mosquitoes

Freshwater ecosystems are positioned at low levels in the landscape and receive large inputs of diverse plant-based detritus, a major source of energy for consumers in aquatic ecosystems. We conducted field experiments in Urbana, IL to determine the independent and combined effects of leaves of common tree species including the northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marshall), and common hackberry (Celtis occidentalis L.) on the performance of container-dwelling mosquitoes, especially Culex restuans Theobald (Diptera: Culicidae). We tested the hypothesis that leaf species have asymmetric effects on adult mosquito production and longevity. Hackberry followed by combined leaf treatments and maple produced the greatest number of pupae, whereas oak leaves produced the fewest. Leaf treatments had no significant effects on adult female sizes but female longevity was significantly lower in oak leaf treatments compared with the other leaf treatments. These findings support the hypothesis that leaf species identity influences the performance of container-dwelling mosquitoes with potential consequences for the transmission of infectious diseases.

Implications for operational control of adult mosquito production in cisterns and wells in St. Augustine, FL using attractive sugar baits

The aim of this study was to further investigate the use of attractive sugar baits as an effective, inexpensive, and environmentally friendly tool for integrated mosquito management programs. Mosquitoes were offered dyed sugar bait in wells and cisterns in an urban tourist area in St. Augustine, FL. Exit traps were constructed to cover the well and cistern openings so the number of resting and emerging mosquitoes stained by feeding on the sugar bait could be monitored. Four mosquito species were collected from these structures: Aedes albopictus (Skuse), Anopheles crucians (Wiedemann), Culex quinquefasciatus Say, and Toxorhynchites rutilus rutilus (Coquillett). Overall, 90% (1482/1644) of the mosquitoes trapped were stained. In general, the number of mosquitoes stained was significantly greater in wells (P<0.0001) and cisterns (P<0.0001) than the numbers that were not stained by the colored bait. Based on the number of mosquitoes stained, we would have expected considerable mosquito mortality had the sugar bait contained an oral toxin. The results of this study support the concept of using attractive toxic sugar baits as an effective tool for integrated mosquito management.

Width of planting beds for emergent vegetation influences mosquito production from a constructed wetland in California (USA)

The abundance and distribution of Culex spp. mosquitoes, mosquito-eating fish (Gambusia affinis), and other macroinvertebrates were assessed within wide (width: 20m) and narrow (width: 3m) bands of California bulrush (Schoenoplectus californicus) and in the open water adjacent to emergent vegetation in two marshes of an ammonia-dominated wastewater treatment wetland in southern California. Emergence traps and minnow traps were used to collect fauna along transects perpendicular to the path of water flow at three distances (1.5, 5 and 10m) from the vegetation–open water interface in the wide bands of emergent vegetation, at the center of narrow bands of emergent vegetation and at 1.5m from the edge of emergent vegetation in the open water. Mosquito production was least from the open water sites and, relative to sites within the wide band of vegetation in each of the two marshes studied, was significantly lower from the narrow bands of emergent vegetation where mosquitofish populations increased comparatively more during the summer and nektonic predatory insects (Notonectidae) were more abundant. Adult mosquito production was greatest at the middle of wide bands of bulrush. Despite an ongoing integrated mosquito management (IMM) program that included routine application of larvicides and adulticides, Culex mosquitoes emerged in large numbers (>200 individuals/m2/day) along transects within the interiors of wide bands of emergent vegetation in the late spring and summer. The width of bands of emergent vegetation in constructed treatment wetlands should be minimized to the greatest extent possible to achieve water quality goals yet to facilitate both ecological and, when necessary, chemical control of mosquitoes.

Is routine dengue vector surveillance in central Brazil able to accurately monitor the Aedes aegypti population? Results from a pupal productivity survey

To assess how well the Aedes aegypti infestation rapid survey, Levantamento Rapido de Indice para Aedes aegypti (LIRAa), is able to accurately estimate dengue vector densities and target the most important breeding sites in Goiania, Brazil. In February 2009, a pupal productivity survey was conducted in 2 districts of the city of Goiania, central Brazil. The results were compared to those of LIRAas conducted in the same districts during the months before and after the pupal productivity survey. In the pupal productivity survey, 2,024 houses were surveyed and 2,969 water-holding containers were inspected. Discarded small water containers most frequently contained immature Ae. aegypti. The most pupal-productive containers were elevated water tanks, roof gutters and water holding roofs. Combined, these three containers accounted for <40% of all positive containers but produced >70% of all pupae. In the two districts where the pupal productivity survey was conducted, the house indices were 5.1 and 4.6 and the Breteau indices were 5.9 and 6.0. In contrast, the two LIRAs conducted in the same two districts resulted in an average house index of 1.5 and Breteau index of 2.5, with discarded items identified as the most frequently infested container type. Both the LIRAa and the pupal productivity survey identified discarded items as being most frequently infested with immature stages of Ae. aegypti, but the pupal productivity survey showed that elevated containers produced the greatest proportion of Ae. aegypti pupae (a proxy measure of adult vector density) and that the values of the Stegomyia indices were substantially underestimated by LIRAa. Although both surveys differ considerably in terms of sampling method and manpower, in the case of this study the LIRAa did not accurately identify or target the containers that were the most important to adult mosquito production.

Effectiveness of pyramidal emergence traps for estimating production of Culex mosquitoes (Diptera:Culicidae)

The percentage of emergent mosquitoes (Culex spp.) collected, temporal dynamics of collection by pyramidal emergence traps, and the effect of a chemical deterrent (pest control strips) for terrestrial scavengers, which remove emergent mosquitoes from collection jars, on the number of emergent mosquitoes collected were studied in ponds in southern California. On average, 75.5% of emergent mosquitoes were collected in jars at the apex of 0.25-m2 emergence traps placed on the water surface. Recently emerged mosquitoes spent ∼1 d in emergence traps before moving into the collection jars. Pest control strips (2.54 cm2 of Vaportape II: 10% 2,2-dichlorovinyl dimethyl phosphate), which have been used in collection jars during previous studies to deter foraging on newly emerged mosquito adults by Argentine ants (Linepithema humile Mayr), did not significantly reduce the number of adult mosquitoes in collection jars and did not delay the movement of adult mosquitoes into collection jars. The cumulative proportion of adult mosquito production sampled by the pyramidal emergence traps increased at a decreasing rate across time (proportion of total production = −0.314 + 1.021(1 − e−0.370t) where t is days of trapping). The proportion of adult mosquito production collected during 3- to 5-d collection periods ranged between 0.37 and 0.55 during periods that Culex emergence was continuous from aquatic habitats.

Effects of road salts on the composition of seasonal pond communities: can the use of road salts enhance mosquito recruitment?

Road deicing agents can enter nearby wetlands and alter the composition of aquatic communities by directly eliminating salt-intolerant species and modifying ecological interactions between tolerant species. We conducted field experiments to examine the sensitivity of taxa that inhabit seasonal wetlands and to determine whether salt contamination could increase the production of ovipositing insects. In two outdoor mesocosm experiments, cladocerans and copepods rarely survived concentrations of commercial road salt >1,200 mg L−1, while wood frog eggs and hatchlings (Lithobates sylvaticus) were not strongly impacted until concentrations exceeded 4,500 mg L−1. Shore flies (Ephydridae), mosquitoes (Culex restuans; Anopheles punctipennis) and midge larvae (Chironomidae) were more salt tolerant than macrozooplankton. These taxa tended to be absent or relatively rare in experimental mesocosms with low salinities, but abundant in mesocosms with intermediate to high salinities. We conducted two additional experiments to examine whether adult choice of oviposition sites may in part explain the rarity of Cx. restuans in pools with low salinity. These revealed that Cx. restuans reduced oviposition rates in water-filled containers with cladocerans, and reduced clutch size in the presence of Lithobates larvae. However, salt concentration per se did not influence the propensity of Cx. restuans to oviposit. Collectively, our results suggest that aquatic habitats that are biologically compromised by deicing agents favor salt-tolerant insects, and that the use of road salts could increase the production of adult mosquitoes that are pests and vectors of disease.

Aedes aegypti in Jamaica, West Indies: container productivity profiles to inform control strategies

To describe the Aedes aegypti container profile in the three parishes of Portland, St. Anns and St. Catherine, Jamaica. Traditional stegomyia and pupae per person indices. A total of 8855 containers were inspected. A. aegypti were breeding in 19.2% of the 4728 containers in Portland, in 6.7% of the 2639 containers in St. Ann, and in 27.2% of the 1488 containers in Tryhall Heights, St. Catherine. Container types differed between Portland (P > 0.02) on one hand and St. Ann and Tryhall Heights, St. Catherine on the other hand: there were with no vases or potted plants with water saucers in St. Ann and St. Catherine. A. aegypti were breeding in more containers in St. Catherine (38%) (38% in wet season and 21% in the dry season) than in Portland (19%) or St. Ann (6%), both of which had more containers but A. aegypti breeding in fewer: 17.7% and 11.2% in the wet and 20.4% and 3.5% in the dry seasons respectively. The daily production of adult mosquitoes in the three study sites was 1.51, 1.29 and 0.66 adult female mosquitoes per person in Portland, St. Ann and St. Catherine during the dry season and 1.12, 0.23 and 1.04 female mosquitoes per person in the wet season respectively. All three communities are at risk for dengue outbreaks and vector control should concentrate on reducing the mosquito populations from the most productive containers before a new dengue virus serotype is introduced into Jamaica.

Spatiotemporal dynamics of immature culicines (subfamily Culicinae) and their larval habitats in Mwea Rice Scheme, Kenya

An ecological study was conducted at three study sites in Mwea Rice Scheme, Kenya to identify the diverse aquatic habitats in which culicine mosquitoes thrived and to explore the best strategies for mosquito control in the area. During the 11-month study period, ten habitat categories and 11 culicine species mainly dominated by Culex quinquefasciatus (72.0%) and Culex annulioris (17.9%) were identified from pupae and late instars larval samples. Two of the 11 culicine species, Ficalbia (Mimomyia) plumosa and Uranotaenia spp., have not been reported previously in the study area. Rurumi had more habitat types than either of the other study sites but the least number of mosquito species. In contrast, Karima had the least number of habitat types but significantly higher density of early instars than the other study sites. The relative abundance of late instars and pupae did not vary significantly among study sites. The contribution of different habitat types to larval production varied markedly between seasons and among study sites. Paddies and canals were perennial contributors of culicine mosquito larvae while the other habitat types were important mainly during the wet season. Some habitat types such as ditches, seeps, marshes, and fishpond were absent in some study sites but of great significance in other study sites. C. quinquefasciatus was positively associated with turbidity at all study sites and also negatively associated with emergent vegetation and distance to the nearest homestead in Karima, emergent vegetation in Kiuria, and other aquatic invertebrates in Rurumi. C. annulioris was positively associated with emergent vegetation at all study sites and also with depth in Kiuria. These findings indicate that besides rice fields and associated habitats, a diversity of other aquatic habitats contribute to culicine adult mosquito production in the study area and that environmental factors that determine the occurrence of a particular mosquito species may vary significantly even among areas of similar land use. This information is critical when designing and implementing mosquito larval control programs.

Standardizing Container Classification for ImmatureAedes aegyptiSurveillance in Kamphaeng Phet, Thailand

For the development of community-based vector control programs for dengue prevention, one of the key components is to formulate an adequate classification scheme for the different containers in which immature Aedes mosquitoes develop. Such a standardized scheme would permit more efficient targeting of efforts and resources in the most productive way possible. Based on field data from Kamphaeng Phet, Thailand, we developed a classification method that consists of the shape (S), use (U), and material (M) of the container (SUM-method). We determined that by targeting the four container classes that held the most Ae. aegypti pupae, adult mosquito production could theoretically be reduced by 70%. The classification method may be equally suitable for similar studies elsewhere in the world. Main advantages of the classification scheme are that categorization of containers does not need to be done a priori, that there is no "miscellaneous" class, and that different immature control strategies can be easily and prospectively tested with a local database. We expect that the classification strategy will 1) facilitate comparison of results among different ecological and geographic settings and 2) simplify communication among vector control personnel and affected communities.

Standardizing Container Classification for Immature &lt;I&gt;Aedes aegypti&lt;/I&gt; Surveillance in Kamphaeng Phet, Thailand

For the development of community-based vector control programs for dengue prevention, one of the key components is to formulate an adequate classification scheme for the different containers in which immature Aedes mosquitoes develop. Such a standardized scheme would permit more efficient targeting of efforts and resources in the most productive way possible. Based on field data from Kamphaeng Phet, Thailand, we developed a classification method that consists of the shape (S), use (U), and material (M) of the container (SUM-method). We determined that by targeting the four container classes that held the most Ae. aegypti pupae, adult mosquito production could theoretically be reduced by 70%. The classification method may be equally suitable for similar studies elsewhere in the world. Main advantages of the classification scheme are that categorization of containers does not need to be done a priori, that there is no "miscellaneous" class, and that different immature control strategies can be easily and prospectively tested with a local database. We expect that the classification strategy will 1) facilitate comparison of results among different ecological and geographic settings and 2) simplify communication among vector control personnel and affected communities.

Effects of Inorganic Nitrogen Enrichment on Mosquitoes (Diptera: Culicidae) and the Associated Aquatic Community in Constructed Treatment Wetlands

Ammonium nitrogen (NH4-N) is a significant component of municipal and agricultural wastewaters, and nitrogen reduction is an important use of constructed treatment wetlands. The effects of ammonium nitrogen enrichment on resources of larval mosquitoes, larval mosquito abundance, adult mosquito production, and the abundance of related wetland organisms were examined in 0.1-ha replicate treatment wetlands. The hypothesis of a bottom-up effect induced by ammonium addition was not supported by bacterial abundance, mean bacterial cell size, or algal biomass in the water column. There was, however, a significant negative correlation between bacterial cell length and Culex tarsalis Coquillett (Diptera: Culicidae) larval abundance 1 wk later in wetlands enriched with ammonium nitrogen. Larval mosquito (Culex spp.) abundance in southern California wetlands enriched with NH4-N (mean approximately equal to 3 mg/liter) was significantly greater than in control wetlands at ambient nitrogen levels (8.3 mg NO3-N/liter, 0.1 mg NH4-N/liter). Adult mosquito production was nine-fold greater and chironomid larvae were significantly more abundant in wetlands enriched with NH4-N than in controls but other censused taxa exhibited no significant trends. Mosquitofish, Gambusia affinis (Baird & Girard), abundance was significantly reduced in enriched wetlands, but other potential mosquito predators were not significantly affected by ammonium enrichment.

Vector-borne diseases and global warming: are both on an upward swing? Scientists are still debating whether global warming will lead to a further spread of mosquitoes and the diseases they transmit.

The effects of global warming have long been a focus of scientists’ attention, not only since the USA rejected the Kyoto Protocol, which was drafted to curb the emission of so‐called greenhouse gases. The potential consequences of increasing the Earth's temperature by just a few degrees include a rise in ocean levels due to melting of the polar ice caps, parching of the land and changes of storm, flood and drought patterns. These scenarios are mainly debated among climatologists, but biologists are adding a further dimension with another potentially disastrous effect. ‘In the past five years, there has been increasing discussion about global warming and its potential impact on diseases like malaria and dengue fever in the tropics and even in temperate zones’, Uriel Kitron, Professor of Epidemiology at the University of Illinois in Urbana‐Champaign, said. Indeed, many scientists point to global warming as a factor in the spread of malaria and other vector‐borne infectious diseases. This camp believes that global warming is likely to disturb a delicate equilibrium and contribute to new epidemics of malaria, yellow and dengue fever and encephalitis. Kitron has been studying the invasion of the tiger mosquito in Illinois, LaCrosse encephalitis in the Great Lakes region, and dengue and malaria in Trinidad, Kenya and Mozambique. His research, however, does not clearly link global warming with the spread of these diseases. ‘Vector‐borne diseases have an extremely complex ecology, which renders transmission and what it takes to produce disease not that simple and clear cut’, he said. > Many scientists believe that global warming is likely to disturb a delicate equilibrium and contribute to new epidemics of malaria, yellow and dengue fever and encephalitis Unlike Kitron's middle‐of‐the‐road view, much of the scientific thinking on the topic is polarised, and seems to be tinged with politics. Paul Epstein, Associate …