Effect of leaf type and pesticide exposure on abundance of bacterial taxa in mosquito larval habitats

Application of QSAR Approach to Assess the Effects of Organic Pollutants on Bacterial Virulence Factors

The release of a wide variety of persistent chemical contaminants into wastewater has become a growing concern due to their potential health and environmental risks. While the toxic effects of these pollutants on aquatic organisms have been extensively studied, their impact on microbial pathogens and their virulence mechanisms remains largely unexplored. This research paper focuses on the identification and prioritization of chemical pollutants that increase bacterial pathogenicity, which is a public health concern. In order to predict how chemical compounds, such as pesticides and pharmaceuticals, would affect the virulence mechanisms of three bacterial strains (Escherichia coli K12, Pseudomonas aeruginosa H103, and Salmonella enterica serovar. Typhimurium), this study has developed quantitative structure-activity relationship (QSAR) models. The use of analysis of variance (ANOVA) functions assists in developing QSAR models based on the chemical structure of the compounds, to predict their effect on the growth and swarming behavior of the bacterial strains. The results showed an uncertainty in the created model, and that increases in virulence factors, including growth and motility of bacteria, after exposure to the studied compounds are possible to be predicted. These results could be more accurate if the interactions between groups of functions are included. For that, to make an accurate and universal model, it is essential to incorporate a larger number of compounds of similar and different structures.

Pesticides drive differential leaf litter decomposition and mosquito colonisation dynamics in lentic conditions

Global contamination of freshwater ecosystems by chemical compounds, such as pesticides, may exert high pressure on biologically-driven organic matter decomposition. These pollutants may also impair the quality of organic substrates for colonising invertebrates and reduce primary productivity by decreasing the abundance of phytoplankton. In southern Africa, increasing pesticide usage associated with macadamia plantations, in particular, presents a growing risk to freshwater ecosystems. Here, we examined macadamia (Macadamia integrifolia) leaf litter decomposition following exposure to three pesticides (i.e., Karate Zeon 10 CS (lambda-cyhalothrin), Mulan 20 AS (acetamiprid), Pyrinex 250 CS (chlorpyrifos)) used commonly in macadamia plantations, via an ex-situ microcosm approach. We examined mosquito colonisation of these microcosms as semi-aquatic macroinvertebrates which form a significant component of aquatic communities within standing waters. Macadamia leaf litter tended to decompose faster when exposed to Karate and Pyrinex pesticide treatments. Additionally, chlorophyll-a, conductivity, total dissolved solids, and pH differed among pesticide treatments and controls, with pesticides (Karate Zeon and Mulan) tending to reduce chlorophyll-a concentrations. Overall, pesticide treatments promoted mosquito (i.e., Culex spp.) and pupal abundances. In terms of dominant aquatic mosquito group abundances (i.e., Anopheles spp., Culex spp.), the effect of pesticides differed significantly among pesticide types, with Pyrinex and Mulan treatments having higher mosquito abundances in comparison to Karate Zeon and pesticide-free treatments. These findings collectively demonstrate that common pesticides used in the macadamia plantation may exert pressure on adjacent freshwater communities by shaping leaf-litter decomposition, semi-aquatic macroinvertebrate colonisation dynamics, and chlorophyll-a.

The larval environment strongly influences the bacterial communities of Aedes triseriatus and Aedes japonicus (Diptera: Culicidae)

Mosquito bacterial communities are essential in mosquito biology, and knowing the factors shaping these bacterial communities is critical to their application in mosquito-borne disease control. This study investigated how the larval environment influences the bacterial communities of larval stages of two container-dwelling mosquito species, Aedes triseriatus, and Aedes japonicus. Larval and water samples were collected from tree holes and used tires at two study sites, and their bacteria characterized through MiSeq sequencing of the 16S rRNA gene. Bacterial richness was highest in Ae. japonicus, intermediate in Ae. triseriatus, and lowest in water samples. Dysgonomonas was the dominant bacterial taxa in Ae. triseriatus larvae; the unclassified Comamonadaceae was dominant in water samples from waste tires, while Mycobacterium and Carnobacterium, dominated Ae. japonicus. The two mosquito species harbored distinct bacterial communities that were different from those of the water samples. The bacterial communities also clustered by habitat type (used tires vs. tree holes) and study site. These findings demonstrate that host species, and the larval sampling environment are important determinants of a significant component of bacterial community composition and diversity in mosquito larvae and that the mosquito body may select for microbes that are generally rare in the larval environment.

Microbial communities of container aquatic habitats shift in response to Culex restuans larvae

We examined how larvae of Culex restuans mosquito influences the bacterial abundance, composition and diversity in simulated container aquatic habitats. The microbiota of Cx. restuans larvae were also characterized and compared to those of their larval habitats. The presence of Cx. restuans larvae altered the bacterial community composition and reduced the bacterial abundance, diversity and richness. Azohydromonas sp., Delftia sp., Pseudomonas sp., Zooglea sp., unclassified Enterobacteriaceae and unclassified Bacteroidales were suppressed while Prosthecobacter sp., Hydrogenaphaga sp., Clostridium sp., unclassified Clostridiaceae and Chryseobacterium sp. were enhanced in the presence of Cx. restuans larvae. Cx. restuans larvae harbored distinct and less diverse bacterial community compared to their larval habitats. These findings demonstrate that Cx. restuans larvae play a key role in structuring the microbial communities in container aquatic habitats and may lower the nutritional quality and alter the decomposition process and food web dynamics in these aquatic systems. The findings also demonstrate that mosquito larvae are highly selective of the bacterial taxa from the larval environment that colonize their bodies. These findings provide new opportunities for more focused studies to identify the specific bacterial taxa that serve as food for mosquito larvae and those that could be harnessed for disease control.

Competition and growth among Aedes aegypti larvae: Effects of distributing food inputs over time

Male and female mosquito larvae compete for different subsets of the yeast food resource in laboratory microcosms. Males compete more intensely with males, and females with females. The amount and timing of food inputs alters both growth and competition, but the effects are different between sexes. Increased density increases competition among males. Among females, density operates primarily by changing the food/larva or total food; this affects competition in some interactions and growth in others. Food added earlier in the life span contributes more to mass than the same quantity added later. After a period of starvation larvae appear to use some of the subsequent food input to rebuild physiological reserves in addition to building mass. The timing of pupation is affected by the independent factors and competition, but not in the same way for the two sexes, and not in the same way as mass at pupation for the two sexes. There is an effect of density on the timing of pupation for females independent of competition or changes in food/larva or total food. Male and female larvae have different larval life history strategies. Males grow quickly to a minimum size, then pupate, depending on the amount of food available. Males that do not grow quickly enough may delay pupation further to grow larger, resulting in a bimodal distribution of sizes and ages. Males appear to have a maximum size determined by the early food level. Females grow faster than males and grow larger than males on the same food inputs. Females affect the growth and competition among males by manipulating the number of particles in the microcosm through changes in feeding behavior. Mosquito larvae appear to have evolved to survive periods of starvation and take advantage of intermittent inputs of food into containers.

Effect of life stage and pesticide exposure on the gut microbiota of Aedes albopictus and Culex pipiens L

Pesticides commonly contaminate the aquatic environments inhabited by mosquito juveniles. However, their role in shaping the mosquito microbiota is not well understood. We hypothesized that environmentally relevant concentrations of atrazine, permethrin and malathion will mediate a shift in the mosquito gut bacterial community structure due to their toxic effect on the aquatic bacterial communities, and reduce mosquito gut bacterial diversity by enriching pesticide-degrading bacterial communities over susceptible taxa. Illumina MiSeq sequencing of the V3-V4 hypervariable regions of the 16 S rRNA gene was used to characterize the microbial communities of larval and adult stages of the two mosquito species and the water samples from microcosms treated with each of the pesticides, separately. Bacterial community composition differed by sample type (larval stage vs. adult stage) and water sampling date (day 3 vs. day 7), but not by pesticide treatment. In larval stages, bacterial OTU richness was highest in samples exposed to malathion, intermediate in permethrin, and lowest in controls. Bacterial richness was significantly higher in larval stages compared to adult stages for all treatments. This study provides a primer for future studies evaluating mosquito microbial responses to exposures to chemical pesticides and the possible implications for mosquito ecology.

Effects of anthropogenic subsidy and glyphosate on macroinvertebrates in streams

Streams and surrounding terrestrial ecosystems are closely linked by numerous resource subsidies including anthropogenic subsidies which are increasingly entering streams due to intensive human activities. Also, streams are threatened by stressors such as glyphosate-the most widely used herbicide worldwide. However, the ecological consequences of anthropogenic subsidies and glyphosate on freshwaters are not fully understood. Here, we deployed leaf litter (Cinnamomum camphora) bags containing neither, either, or both treatments of anthropogenic carrion subsidy (chicken meat) and glyphosate (coated in agar) in four streams, which had different land use (i.e., forest, village, and suburban) in Huangshan, Anhui Province, China. We aimed to investigate the individual and combined effects of anthropogenic carrion subsidy and glyphosate on macroinvertebrates in streams and whether these effects differ with land use change. Macroinvertebrate communities significantly differed among streams: biodiversity index and total taxon richness were highest in village streams and lowest in suburban stream. Overall effects of carrion subsidy and glyphosate on macroinvertebrates were not significant. However, several taxa were affected in one or more streams by the individual or combined effects of carrion subsidy and glyphosate, indicating the importance of local community structure and physical habitats in driving the response of macroinvertebrates to carrion subsidy and glyphosate. Collectively, these results imply that the effects of carrion subsidy and glyphosate on macroinvertebrates are site-specific, and future studies should cover more streams and last longer time to better understand the ecological mechanisms driving such pattern.

Discovery and exploitation of a natural ecological trap for a mosquito disease vector

Ecological traps occur due to a mismatch between a habitat's attractiveness and quality, wherein organisms show preference for low-quality habitats over other available high-quality habitats. Our previous research identified leaf litter from common blackberry (Rubus allegheniensis) as a natural ecological trap for an important vector for West Nile virus (Culex pipiens), attracting mosquitoes to oviposit in habitats deleterious to the survival of their larvae. Here we demonstrate that manipulation of leaf litter in stormwater catch basins, an important source of disease vector mosquitoes in urban environments, can increase Cx. pipiens oviposition but reduce survival. In a series of experiments designed to elucidate the mechanisms that explain the attractive and lethal properties of this native plant, behavioural bioassays suggest that oviposition site selection by Cx. pipiens is mediated primarily by chemical cues as leaves decompose. However, we also show that juvenile mosquito survival is mainly related to the suitability of the bacterial community in the aquatic habitat for mosquito nutritional needs, which does not appear to create a cue that influences oviposition choice. This mismatch between oviposition cues and drivers of larval habitat quality may account for the ecological trap phenomenon detected in this study. Our findings provide new insights into potential mechanistic pathways by which ecological traps may occur in nature and proof-of-concept for a new 'attract-and-kill' tool for mosquito control.

Competition among Aedes aegypti larvae

Adult Aedes aegypti mosquitoes are important vectors of human disease. The size of the adult female affects her success, fitness, and ability to transmit diseases. The size of the adults is determined during the aquatic larval stage. Competition among larvae for food influences the size of the pupa and thus the adult. In these experiments, the food level (mg/larva) and the density (larvae/vial) both affect intraspecific competition, which shows up as the interaction of the two factors. Furthermore, the total food per vial affects the nature of competition among the larvae, also apparent in the interaction of food and density. Male larvae are affected by the percent of males in the vial, but females are not. Seven biologically significant dependent variables were examined, and the data analyzed by multivariate analysis of variance to gain insight into the relationships among the variables and the effects of these factors on the larvae as they grew in small containers. Male and female larvae compete differently from one another for the particulate yeast cells in this experiment; female larvae outcompete males through larger size and by retaining cells within their gut at low total food levels. Under conditions of more intense competition, the pupal masses of both males and females are smaller, so the effect of competition is a reduced apparent food level. The age at pupation is also affected by food and density. Across the twenty treatment combinations of food/larva and larvae/vial, female larvae grew as though there were six different ecological environments while male larvae grew as though there were only four different environments. No interference competition was observed. Eradication efforts aimed at adult populations of this mosquito may inadvertently increase the size and robustness of the next generation of larvae, resulting in a subsequent adult population increase in the second generation.

Changes in Larval Mosquito Microbiota Reveal Non-target Effects of Insecticide Treatments in Hurricane-Created Habitats

Ephemeral aquatic habitats and their associated microbial communities (microbiomes) play important roles in the growth and development of numerous aquatic insects, including mosquitoes (Diptera). Biological control agents, such as Bacillus thuringiensis israelensis (Bti) or insect growth regulators (e.g., methoprene), are commonly used to control mosquitoes in these habitats. However, it is unknown how commonly used control compounds affect the mosquito internal microbiome and potentially alter their life history traits. The objectives of this study were threefold: characterize the internal microbiota of Aedes larvae (Culicidae) in ephemeral forested mosquito habitat using high-throughput amplicon based sequencing, assess how mosquito control treatments affect the internal microbial communities of larval mosquitoes, and determine if changes to the microbiome resulted from direct or indirect treatment effects. The larval microbiome varied in community composition and diversity with development stage and treatment, suggesting potential effects of control compounds on insect microbial ecology. While microbial community differences due to Bti treatment were a result of indirect effects on larval development, methoprene had significant impacts on bacterial and algal taxa that could not be explained by indirect treatment effects. These results provide new information on the interactions between pesticide treatments and insect microbial communities.

Effect of pesticides on microbial communities in container aquatic habitats

Container aquatic habitats support a specialized community of macroinvertebrates (e.g. mosquitoes) that feed on microbial communities associated with decaying organic matter. These aquatic habitats are often embedded within and around agricultural lands and are frequently exposed to pesticides. We used a microcosm approach to examine the single and combined effects of two herbicides (atrazine, glyphosate), and three insecticides (malathion, carbaryl, permethrin) on microbial communities of container aquatic habitats. MiSeq sequencing of the V4 region of both bacterial and archaeal 16S rRNA gene was used to characterize the microbial communities of indoor microcosms that were either exposed to each pesticide alone, a mix of herbicides, a mix of insecticides, or a mix of all five insecticides. Individual insecticides but not herbicides reduced the microbial diversity and richness and two insecticides, carbaryl and permethrin, also altered the microbial community structure. A mixture of herbicides had no effect on microbial diversity or structure but a mixture of insecticides or all five pesticides reduced microbial diversity and altered the community structure. These findings suggest that exposure of aquatic ecosystems to individual pesticides or their mixtures can disrupt aquatic microbial communities and there is need to decipher how these changes affect resident macroinvertebrate communities.

Antibacterial Compounds-Macrolactin Alters the Soil Bacterial Community and Abundance of the Gene Encoding PKS

Macrolactin produced by many soil microbes has been shown to be an efficient antibacterial agent against many bacterial pathogens. However, studies examining the effect of macrolactin on both the soil bacterial community and the intrinsic bacterial species that harbor genes responsible for the production of this antibiotic have not been conducted so far. In this study, a mixture of macrolactin was isolated from the liquid culture of Bacillus amyloliquefaciens NJN-6, and applied to the soil once a week for four weeks. 16S rRNA Illumina MiSeq sequencing showed that continuous application of macrolactin reduced the α-diversity of the soil bacterial community and thereby changed the relative abundance of microbes at both the phylum and genus level. The relative abundance of Proteobacteria and Firmicutes was significantly increased along with a significant decrease in the relative abundance of Acidobacteria. However, the application of macrolactins had an insignificant effect on the total numbers of bacteria. Further, the native gene responsible for the production of macrolactin, the gene encoding polyketide synthase was reduced in copy number after the application of macrolactin. The results of this study suggested that a bactericide from a microbial source could decrease the diversity of the soil bacterial community and change the bacterial community structure. Moreover, the populations of the intrinsic bacterial species which harbor genes responsible for macrolactin production were inhibited when the external source antibiotic was applied.

Effect of two commercial herbicides on life history traits of a human disease vector, Aedes aegypti, in the laboratory setting

Some mosquito species utilize the small niches of water that are abundant in farmland habitats. These niches are susceptible to effects from agricultural pesticides, many of which are applied aerially over large tracts of land. One principal form of weed control in agricultural systems involves the development of herbicide-tolerant crops. The impact of sub-agricultural levels of these herbicides on mosquito survival and life-history traits of resulting adults have not been determined. The aim of this study was to test the effect of two commercial herbicides (Beyond and Roundup) on the survivorship, eclosion time, and body mass of Aedes aegypti. First instar A. aegypti larvae were exposed to varying concentrations (270, 550 and 820 μg/m(2) of glyphosate and 0.74, 1.49, 2.24 μL imazamox/m(2)), all treatments being below recommended application rates, of commercial herbicides in a controlled environment and resulting adult mosquitoes were collected and weighed. Exposure to Roundup had a significant negative effect on A. aegypti survivorship at medium and high sub-agricultural application concentrations, and negatively affected adult eclosion time at the highest concentration. However, exposure to low concentrations of Beyond significantly increased A. aegypti survivorship, although adult female mass was decreased at medium sub-agricultural concentrations. These results demonstrate that low concentrations of two different herbicides, which can occur in rural larval habitats as a result of spray drift, can affect the same species of mosquito in both positive and negative ways depending on the herbicide applied. The effects of commercial herbicides on mosquito populations could have an important effect on disease transmission within agricultural settings, where these and other herbicides are extensively applied to reduce weed growth.

Impact of an Alien Invasive Shrub on Ecology of Native and Alien Invasive Mosquito Species (Diptera: Culicidae)

We examined how leaf litter of alien invasive honeysuckle (Lonicera maackii Rupr.) either alone or in combination with leaf litter of one of two native tree species, sugar maple (Acer saccharum Marshall) and northern red oak (Quercus rubra L.), affects the ecology of Culex restuans Theobald, Ochlerotatus triseriatus Say, and Ochlerotatus japonicus Theobald. Experimental mesocosms containing single species litter or a mixture of honeysuckle and one of two native tree species litter were established at South Farms and Trelease Woods study sites in Urbana, IL, and examined for their effect on 1) oviposition site selection by the three mosquito species, and 2) adult production and body size of Oc. triseriatus and Oc. japonicus. There were no significant effects of study site and leaf treatment on Oc. japonicus and Oc. triseriatus oviposition preference and adult production. In contrast, significantly more Cx. restuans eggs rafts were collected at South Farms relative to Trelease Woods and in honeysuckle litter relative to native tree species litter. Significantly larger adult females of Oc. japonicus and Oc. triseriatus were collected at South Farms relative to Trelease Woods and in honeysuckle litter relative to native tree species litter. Combining honeysuckle litter with native tree species litter had additive effects on Cx. restuans oviposition preference and Oc. japonicus and Oc. triseriatus body size, with the exception of honeysuckle and northern red oak litter combination, which had antagonistic effects on Oc. triseriatus body size. We conclude that input of honeysuckle litter into container aquatic habitats may alter the life history traits of vector mosquito species.

Developmental succession of the microbiome of Culex mosquitoes

Background

The native microflora associated with mosquitoes have important roles in mosquito development and vector competence. Sequencing of bacterial V3 region from 16S rRNA genes across the developmental stages of Culex mosquitoes (early and late larval instars, pupae and adults) was used to test the hypothesis that bacteria found in the larval stage of Culex are transstadially transmitted to the adult stage, and to compare the microbiomes of field-collected versus laboratory-reared mosquitoes.

Results

Beta diversity analysis revealed that bacterial community structure differed among three life stages (larvae, pupae and adults) of Culex tarsalis. Although only ~2 % of the total number of bacterial OTUs were found in all stages, sequences from these OTUs accounted for nearly 82 % of the total bacterial sequences recovered from all stages. Thorsellia (Gammaproteobacteria) was the most abundant bacterial taxon found across all developmental stages of field-collected Culex mosquitoes, but was rare in mosquitoes from laboratory-reared colonies. The proportion of Thorsellia sequences in the microbiomes of mosquito life stages varied ontogenetically with the greatest proportions recovered from the pupae of C. tarsalis and the lowest from newly emerged adults. The microbiome of field-collected late instar larvae was not influenced significantly by differences in the microbiota of the habitat due to habitat age or biopesticide treatments. The microbiome diversity was the greatest in the early instar larvae and the lowest in laboratory-reared mosquitoes.

Conclusions

Bacterial communities in early instar C. tarsalis larvae were significantly more diverse when compared to late instar larvae, pupae and newly emerged adults. Some of the bacterial OTUs found in the early instar larvae were also found across developmental stages. Thorsellia dominated the bacterial communities in field-collected immature stages but occurred at much lower relative abundance in adults. Differences in microbiota observed in larval habitats did not influence bacterial community profiles of late instar larvae or adults. However, bacterial communities in laboratory-reared C. tarsalis larvae differed significantly from the field. Determining the role of Thorsellia in mosquitoes and its distribution across different species of mosquitoes warrants further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-015-0475-8) contains supplementary material, which is available to authorized users.

Asymmetric effects of native and exotic invasive shrubs on ecology of the West Nile virus vector Culex pipiens (Diptera: Culicidae)

Background

Exotic invasive plants alter the structure and function of native ecosystems and may influence the distribution and abundance of arthropod disease vectors by modifying habitat quality. This study investigated how invasive plants alter the ecology of Culex pipiens, an important vector of West Nile virus (WNV) in northeastern and midwestern regions of the United States.

Methods

Field and laboratory experiments were conducted to test the hypothesis that three native leaf species (Rubus allegheniensis, blackberry; Sambucus canadensis, elderberry; and Amelanchier laevis, serviceberry), and three exotic invasive leaf species (Lonicera maackii, Amur honeysuckle; Elaeagnus umbellata, autumn olive; and Rosa multiflora, multiflora rose) alter Cx. pipiens oviposition site selection, emergence rates, development time, and adult body size. The relative abundance of seven bacterial phyla in infusions of the six leaf species also was determined using quantitative real-time polymerase chain reaction to test the hypothesis that variation in emergence, development, and oviposition site selection is correlated to differences in the diversity and abundance of bacteria associated with different leaf species, important determinants of nutrient quality and availability for mosquito larvae.

Results

Leaf detritus from invasive honeysuckle and autumn olive yielded significantly higher adult emergence rates compared to detritus from the remaining leaf species and honeysuckle alleviated the negative effects of intraspecific competition on adult emergence. Conversely, leaves of native blackberry acted as an ecological trap, generating high oviposition but low emergence rates. Variation in bacterial flora associated with different leaf species may explain this asymmetrical production of mosquitoes: emergence rates and oviposition rates were positively correlated to bacterial abundance and diversity, respectively.

Conclusions

We conclude that the displacement of native understory plant species by certain invasive shrubs may increase production of Cx. pipiens with potential negative repercussions for human and wildlife health. These findings may be relevant to mosquito control and invasive plant management practices in the geographic range of Cx. pipiens. Further, our discovery of a previously unknown ecological trap for an important vector of WNV has the potential to lead to novel alternatives to conventional insecticides in mosquito control by exploiting the apparent “attract-kill” properties of this native plant species.

Bacterial Communities and Midgut Microbiota Associated with Mosquito Populations from Waste Tires in East-Central Illinois

Mosquito-microbe interactions tend to influence larval nutrition, immunity, and development, as well as fitness and vectorial capacity of adults. Understanding the role of different bacterial species not only improves our knowledge of the physiological and ecological consequences of these interactions, but also provides the basis for developing novel strategies for controlling mosquito-borne diseases. We used culture-dependent and culture-independent techniques to characterize the bacterial composition and abundance in water and midgut samples of larval and adult females of Aedes japonicus (Theobald), Aedes triseriatus (Say), and Culex restuans (Theobald) collected from waste tires at two wooded study sites in Urbana, IL. The phylum-specific real-time quantitative polymerase chain reaction assay revealed a higher proportion of Actinobacteria and a lower proportion of gamma-Proteobacteria and Bacteroidetes in water samples and larval midguts compared to adult female midguts. Only 15 of the 57 bacterial species isolated in this study occurred in both study sites. The number of bacterial species was highest in water samples (28 species from Trelease Woods; 25 species from South Farms), intermediate in larval midguts (13 species from Ae. japonicus; 12 species from Ae. triseriatus; 8 species from Cx. restuans), and lowest in adult female midguts (2 species from Ae. japonicus; 3 species from Ae. triseriatus). These findings suggest that the composition and richness of bacterial communities varies both between habitats and among mosquito species and that the reduction in bacteria diversity during metamorphosis is more evident among bacteria detected using the culture-dependent method.

Sublethal effects of atrazine and glyphosate on life history traits of Aedes aegypti and Aedes albopictus (Diptera: Culicidae)

Although exposure of mosquito larvae to agricultural chemicals such as herbicides is common and widespread, our understanding of how these chemicals affect mosquito ecology and behavior is limited. This study investigated how an environmentally relevant concentration of two herbicides, atrazine and glyphosate, affects mosquito life history traits. One hundred and fifty (150) first instar Aedes (Stegomyia) aegypti (L.) or Aedes (Stegomyia) albopictus (Skuse) larvae were reared in 1.6 L of live oak leaf (Quercus virginiana) infusion in the presence (5 mg/L) or absence (0 mg/L) of atrazine or glyphosate. The containers were monitored daily to determine the emergence rates, sex ratio, male and female emergence times, and female body size. Emergence rates of A. aegypti from atrazine treatment were significantly higher relative to either glyphosate or control treatments (A. aegypti: atrazine = 93 ± 6% (±95% CI), glyphosate = 82 ± 5%, control = 78 ± 5%), while emergence rates of A. albopictus in atrazine treatments were significantly higher than in glyphosate treatments but not in controls (A. albopictus: atrazine = 84 ± 5 %, glyphosate = 76 ± 4%, control = 78 ± 4%). For both mosquito species, a sex ratio distortion with male bias was observed in control and glyphosate treatments, but not in atrazine treatments (A. aegypti: atrazine = 0.90 ± 0.17 (±SE), glyphosate = 1.63 ± 0.21, control = 1.69 ± 0.26; A. albopictus: atrazine = 1.09 ± 0.08, glyphosate = 1.88 ± 0.12, control = 1.37 ± 0.11). Emergence times for both sexes of the two mosquito species were significantly longer in atrazine treatments compared to glyphosate or control treatments (A. aegypti: females: atrazine = 11.20 ± 0.50 (days ± 95 % CI), glyphosate = 9.71 ± 0.23, control = 9.87 ± 0.21; males: atrazine = 9.46 ± 0.27, glyphosate = 8.80 ± 0.25, control = 8.85 ± 0.24; A. albopictus: females: atrazine = 17.40 ± 1.70, glyphosate = 12.4 ± 0.40, control = 12.5 ± 0.30; males: atrazine = 12.96 ± 0.41, glyphosate = 10.48 ± 0.24, control = 10.64 ± 0.37). For A. albopictus but not A. aegypti, adult females from atrazine treatment had significantly longer wing lengths compared to those from glyphosate or control treatments (A. albopictus: atrazine = 3.06 ± 0.07 (mm ± 95% CI), glyphosate = 2.80 ± 0.07, control = 2.83 ± 0.06). These results demonstrate the potential for atrazine, a widely used herbicide, to influence epidemiologically relevant life history traits of mosquitoes.