The effects of plant essential oils on escape response and mortality rate of Aedes aegypti and Anopheles minimus

The High Throughput Screening System (HITSS) has been applied in insecticide behavioral response studies with various mosquito species. In general, chemical or natural compounds can produce a range of insect responses: contact irritancy, spatial repellency, knock‐down, and toxicity. This study characterized these actions in essential oils derived from citronella, hairy basil, catnip, and vetiver in comparison to DEET and picaridin against Aedes aegypti and Anopheles minimus mosquito populations. Results indicated the two mosquito species exhibited significantly different (P<0.05) contact irritant escape responses between treatment and control for all tested compound concentrations, except with the minimum dose of picaridin (P>0.05) against Ae. aegypti. Spatial repellency responses were elicited in both mosquito species when exposed to all compounds, but the strength of the repellent response was dependent on compound and concentration. Data show that higher test concentrations had greatest toxic effects on both mosquito populations, but vetiver had no toxic effect on Ae. aegypti and picaridin did not elicit toxicity in either Ae. aegypti or An. minimus at any test concentration. Ultimately, this study demonstrates the ability of the HITSS assay to guide selection of effective plant essential oils for repelling, irritating, and killing mosquitoes.     

Evaluation of collection methods for Culex quinquefasciatus,Aedes aegypti,and Aedes simpsoni in northeastern Tanzania

In East Africa, significant morbidity and mortality are caused by infections spread by Culex quinquefasciatus and Aedes aegypti. Sticky traps have been shown to be effective tools for sampling populations of Aedes mosquitoes and have been found to catch Cx. quinquefasciatus. Thus, they could potentially be used to sample populations of this species. This study compared Sticky ovitraps (SO) and MosquiTraps (MQT) with the CDC Gravid trap (CDC‐GT) for collection of Culex and Aedes mosquito populations in Tanzania. A follow‐up experiment was carried out using traps set for a 24‐h period to accommodate the oviposition habits of Aedes aegypti and Ae. simpsoni s.l. mosquitoes. The results showed that the CDC‐GT caught significantly more Cx. quinquefasciatus and Ae. aegypti than the SO or MQT, but there was no significant difference in the number of mosquitoes caught between the two sticky traps or of Ae. simpsoni s.l. caught among the three trap types. The results suggest that CDC‐GTs are the most appropriate in sampling of Cx. quinquefasciatus. Although CDC‐GTs collected more Ae. aegypti than the sticky traps, the simplicity and cost benefit of sticky traps facilitates large scale studies. All three trap types should be considered for monitoring Aedes mosquitoes.     

Synergistic repellent and irritant effect of combined essential oils on Aedes aegypti (L.) mosquitoes

This study was designed to compare the behavioral responses of Aedes aegypti to a single essential oil and to a mixture of two or three essential oils using an excito‐repellency test chamber. Mixtures were prepared from essential oils extracted from Litsea cubeba (LC), Litsea salicifolia (LS), and Melaleuca leucadendron (ML). In general, the mixture of essential oils produced a much stronger escape response by Ae. aegypti, regardless of the test conditions. No significant difference in escape responses was seen when the mixture of oils was compared with a standard commercial product containing DEET. Greater contact irritancy was seen from mixed oils of LC and LS than with other mixed oils. Mixtures of LC and LS at 0.075% showed the highest synergistic action (65.5% escaped) compared to that with unmixed oil alone at the same concentration (LC/20% and LS=32.2%). In addition, mixtures of LC and LS at 0.075% demonstrated the highest non‐contact repellency (62.7%) and showed a greater effect than the use of LC (20%) or LS (20.3%) alone. We conclude that mixtures of two essential oils show potential as active ingredients for mosquito repellents.     

Frequency of pyrethroid resistance in Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Thailand

Thirty‐two Aedes aegypti populations collected throughout Thailand and five populations of Aedes albopictus from southern Thailand were subjected to standard WHO contact bioassays to assess susceptibility to three commonly used synthetic pyrethroids: permethrin, deltamethrin, and lambda‐cyhalothrin. A wide degree of physiological response to permethrin was detected in Ae. aegypti, ranging from 56.5% survival (Lampang, northern Thailand) to only 4% (Kalasin in northeastern and Phuket in southern Thailand). All 32 populations of Ae. aegypti were found to have evidence of incipient resistance (62.5%) or levels of survival deemed resistant (37.5%) to permethrin. Four populations of Ae. albopictus were found with incipient resistance (97 – 80% mortality) and one with resistance (< 80%) to permethrin. The majority of Ae. aegypti populations (68.7%) was susceptible (> 98% mortality) to deltamethrin, with incipient resistance (observed 97–82% mortality) in other localities. In contrast, all populations of Ae. aegypti were completely susceptible (100% mortality) to the recommended operational dosage of lambda‐cyhalothrin. All five populations of Ae. albopictus were found completely susceptible to both deltamethrin and lambda‐cyhalothrin. Evidence of defined incipient or resistance to synthetic pyrethroids mandates appropriate response and countermeasures to mitigate further development and spread of resistance. In light of these findings, we conclude that routine and comprehensive susceptibility monitoring of dengue mosquito vectors to synthetic pyrethroids should be a required component of resistance management policies and disease control activities.     

Field evaluations of disposable sticky lures for surveillance of Aedes aegypti (Stegomyia aegypti) and Culex quinquefasciatus in Jakarta

From December 1997 to April 1998, disposable sticky lures (1608 lure days) were trialled in homes in north Jakarta, Indonesia as surveillance tools for Aedes aegypti (Stegomyia aegypti) (Diptera: Culicidae) and Culex quinquefasciatus (Diptera: Culicidae), referenced to indoor resting adult collections (92 × 10 min). The lures collected 89.4% of the total of 1339 Ae. aegypti and 92.1% of the total of 1272 Cx. quinquefasciatus collected by all methods. Because there were no significant differences with respect to numbers collected in bedrooms, living rooms and kitchens, bedrooms were selected for subsequent trials for reasons of convenience. The main trials involved a replicated complete block design with L‐lysine and sodium carbonate. Lures without attractant or with four different dilutions of L‐lysine collected 3.4–8.5 times more Ae. aegypti and 4.2–8.1 times more Cx. quinquefasciatus than were collected by mouth aspirator. Lures with or without dilutions of sodium carbonate collected 2.7–5.0 times more Ae. aegypti and 1.8–4.2 times more Cx. quinquefasciatus than aspirator collections. The precision associated with catches of sticky lures was better than that for aspirator collections. Although olfactants generally improved the numbers of mosquitoes collected, the differences in catch between lures with and without attractants were usually non‐significant. Any deficit in catch may be offset by increasing the surveillance period to ≥30 days to detect all four dengue serotypes from infected mosquitoes.     

Influence of resource levels,organic compounds and laboratory colonization on interspecific competition between the Asian tiger mosquito Aedes albopictus (Stegomyia albopicta) and the southern house mosquito Culex quinquefasciatus

The mosquitoes Aedes albopictus (Stegomyia albopicta) (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae) are common inhabitants of tyres and other artificial containers, which constitute important peridomestic mosquito breeding habitats. We tested the hypotheses that interspecific resource competition between the larvae of these species is asymmetrical, that the concentration of chemicals associated with decomposing detritus affects the competitive outcomes of these species, and that wild and colonized strains of Cx. quinquefasciatus are affected differently by competition with Ae. albopictus. We conducted two laboratory competition experiments wherein we measured survivorship and estimated population growth (λ′) in both species under multiple mixed‐species densities. Under varying resource levels, competition was asymmetrical: Ae. albopictus caused competitive reductions or exclusions of Cx. quinquefasciatus under conditions of limited resources. In a second experiment, which used both wild and colonized strains of Cx. quinquefasciatus, organic chemical compounds associated with decomposing detritus did not affect the competitive outcome. The colonized strain of Cx. quinquefasciatus had greater survivorship and adult mass, and faster development times than the wild strain, but both strains were similarly affected by competition with Ae. albopictus. Competition between these species may have important consequences for vector population dynamics, especially in areas in which tyres and artificial containers constitute the majority of mosquito breeding habitats.     

Excito‐repellency of essential oils against an Aedes aegypti (L.) field population in Thailand

An investigation of the behavioral responses of Aedes aegypti (= Stegomyia aegypti) to various concentrations of essential oils (2.5, 5, and 10%) extracted from hairy basil (Ocimum americanum Linn), ginger (Zingiber officinale Roscoe), lemongrass (Cymbopogon citratus Stapf), citronella grass (Cymbopogon nardus Rendle), and plai (Zingiber cassumunar Roxb) were performed using an excito‐repellency test chamber. Results showed that Ae. aegypti exhibited varying levels of escape response in both the contact and noncontact chambers in response to different essential oils. The magnitude of the behaviors changed in a dose‐response fashion depending on the percent volume to volume concentration of oil used. A 2.5% concentration of hairy basil oil produced a significantly greater escape response compared to the other extracts at the same concentration (P< 0.05). Oils of ginger, lemongrass, and citronella produced stronger irritant and repellent responses at the median 5% concentration compared to the lowest and highest concentrations. There was marked suppression of escape for both contact and noncontact tests using 10% concentrations of hairy basil, lemongrass, and citronella, with high knockdown for all three oils after 30 min. Hairy basil and lemongrass had the highest insecticidal activity to Ae. aegypti, with LC₅₀ values of 6.3 and 6.7 percent, respectively. We conclude that the essential oils from native plants tested, and likely many other extracts found in plants, have inherent repellent and irritant qualities that should to be screened and optimized for their behavior‐modifying properties against Ae. aegypti and other biting arthropods of public health and pest importance.     

Irritability and repellency of synthetic pyrethroids on an Aedes aegypti population from Thailand

The main objective of this study was to find the optimal dosage of deltamethrin, cyphenothrin, d‐tetramethrin, and tetramethrin that would elicit repellency and irritability responses of Aedes aegypti. The F1‐F3 generations of field mosquitoes collected from Pu Teuy Village, Sai‐Yok District, Kanchanaburi Province, Thailand, were tested with four pyrethroids to determine the LC₂₅, LC₅₀, and LC₉₉. These concentrations were 0.010%, 0.020%, and 0.055%, respectively, for deltamethrin; 0.113%, 0.167%, and 0.353%, respectively, for cyphenothrin; 2.091%, 2.770%, and 5.114%, respectively, for d‐tetramethrin; and 2.377%, 4.251%, and 10.715%, respectively, for tetramethrin. All dosages were tested in the excito‐repellency system. Survival analysis was used to compare each chamber of the test. It was found that cyphenothrin had a stronger repellent effect than the other pyrethroids, while the contact irritant effect was similar among compounds tested. The LC₅₀ of each pyrethroid was found to be the optimal dose for repelling Ae. aegypti. There was no significant difference in LC₉₉ values for either non‐contact or contact trials for each pyrethroid.     

Septic tanks as larval habitats for the mosquitoes Aedes aegypti and Culex quinquefasciatus in Playa‐Playita,Puerto Rico

Adult Aedes aegypti (Linnaeus) (Diptera: Culicidae) were previously recovered from emergence traps on septic tanks in southeastern Puerto Rico. In this study we quantified immature mosquito abundance and its relationship with structural variables of the septic tanks and chemical properties of the water containing raw sewage. A miniaturized floating funnel trap was used to sample 89 septic tanks for larvae in the Puerto Rican community of Playa‐Playita. Aedes aegypti larvae were recovered from 18% of the sampled tanks (10.3 larvae per septic tank per day). Larval presence was positively associated with cracking of the septic tank walls and uncovered access ports. Larval abundance was positively associated with cracking of the septic tank walls and larger tank surface areas, and inversely associated with the total dissolved solids (TDS). Culex quinquefasciatus (Say) larvae were also recovered from 74% of the septic tanks (129.6 larvae per septic tank per day). Larval presence was negatively associated with TDS in the water and larval abundance was positively associated with cracking of the septic tank walls. A screened, plastic emergence trap was used to sample 93 septic tanks within the community for Ae. aegypti and Cx. quinquefasciatus adults. Aedes aegypti adults were recovered from 49% of the sampled tanks (8.7 adults per septic tank per day) and Cx. quinquefasciatus adults were recovered from 97% of the sampled tanks (155.5 adults per septic tank per day). Aedes aegypti adult presence was positively associated with cracking, uncapped openings and septic water pH. The Ae. aegypti adult counts were positively associated with cracking and inversely associated with TDS and conductivity. This study marks the first published record of the recovery of Ae. aegypti larvae from holding tanks containing raw sewage in the Caribbean region. Our study indicates that Ae. aegypti larvae are present in sewage water and that septic tanks have at least the potential to maintain dengue transmission during the dry season.     

Incrimination of the mosquito,Aedes taeniorhynchus,as the primary vector of heartworm,Dirofilaria immitis,in coastal Yucatan,Mexico

Mosquito collections were carried out on microfilaraemic dogs, positive for Dirofilaria sp., for 18 consecutive nights in the coastal town of Celestún, Yucatan, southeast Mexico, during the rainy season (August) of 2007. A total of 292 female mosquitoes representing 12 species of dipteran Culicidae were collected: Anopheles albimanus (Wiedemann); Anopheles crucians (Wiedemann); Anopheles pseudopunctipennis (Theobald); Culex coronator (Dyar & Knab); Culex interrogator (Dyar & Knab); Culex nigripalpus (Theobald); Culex quinquefasciatus (Say); Culex salinarius (Coquillett); Aedes aegypti (Linnaeus); Aedes scapularis (Rondani); Aedes sollicitans (Walker), and Aedes taeniorhynchus (Wiedemann). Aedes taeniorhynchus and Cx. quinquefasciatus were the species found most commonly feeding on the dogs. Filarial nematodes were observed by microscopy in nine of the mosquito species collected; however, third‐instar larvae were only observed in Ae. taeniorhynchus and An. crucians. Of 76 Ae. taeniorhynchus specimens found positive for Dirofilaria sp. by dissection, 14 were confirmed to be positive for Dirofilaria immitis (Leidy) by polymerase chain reaction (PCR). The resulting infection rate for D. immitis confirmed by PCR (6.2%) is higher than any infection rate for Ae. taeniorhynchus previously reported from the Americas.     

Laboratory evaluation of lactic acid on attraction of Culex spp. (Diptera: Culicidae)

The role of lactic acid was evaluated for attraction of Culex nigripalpus, Culex quinquefasciatus, Culex tarsalis, and Aedes aegypti in the laboratory using a dual‐port olfactometer. When lactic acid was combined with chicken odor, attraction was increased for Cx. quinquefasciatus compared to chicken odor alone but not for Cx. nigripalpus, Cx. tarsalis, and Ae. aegypti. Lactic acid combined with hand odor did not change attraction of Cx. tarsalis and Ae. aegypti but decreased attraction of Cx. nigripalpus and Cx. quinquefasciatus. The addition of lactic acid to CO₂ increased attraction of Ae. aegypti and Cx. quinquefasciatus but reduced attraction of Cx. nigripalpus and Cx. tarsalis. Use of commercial lactic acid baits with CO₂ resulted in a similar trend except for Cx. nigripalpus which showed no difference. A blend of lactic acid, acetone, and dimethyl disulfide was attractive to Ae. aegypti (63.4%) but elicited low responses by all Culex spp. (1.3–26.8%). Addition of the blend to CO₂ increased attraction of Ae. aegypti and Cx. quinquefasciatus but reduced attraction of Cx. nigripalpus and Cx. tarsalis. The mixture of compounds plus CO₂ was as attractive as a hand for Cx. quinquefasciatus, Cx. tarsalis, and Ae. aegypti.     

The distribution of mosquitoes across an altitudinal gradient in the Galapagos Islands

An avian malaria parasite (genus Plasmodium) has been detected consistently in the Galapagos Penguin (Spheniscus mendiculus) and less frequently in some passerines. We sampled three resident mosquito species (Aedes taeniorhynchus, Culex quinquefasciatus, and Aedes aegypti) using CDC light and gravid traps on three islands in 2012, 2013, and 2014. We sampled along altitudinal gradients to ask whether there are mosquito‐free refugia at higher elevations as there are in Hawaii. We captured both Ae. taeniorhynchus and Cx. quinquefasciatus at all sites. However, abundances differed across islands and years and declined significantly with elevation. Aedes aegypti were scarce and limited to areas of human inhabitation. These results were corroborated by two negative binomial regression models which found altitude, year, trap type, and island as categorized by human inhabitation to be significant factors influencing the distributions of both Ae. taeniorhynchus and Cx. quinquefasciatus. Annual differences at the highest altitudes in Isabela and Santa Cruz indicate the lack of a stable highland refuge if either species is found to be a major vector of a parasite, such as avian malaria in Galapagos. Further work is needed to confirm the vector potential of both species to understand the disease dynamics of avian malaria in Galapagos.     

Oviposition substrate selection by Florida mosquitoes in response to pathogen‐infected conspecific larvae

The impact of the presence of larval mosquito pathogens with potential for biological control on oviposition choice was evaluated for three mosquito species/pathogen pairs present in Florida. These included Aedes aegypti infected with Edhazardia aedis, Aedes albopictus infected with Vavraia culicis, and Culex quinquefasciatus infected with Culex nigripalpus nucleopolyhedrovirus (CuniNPV). Two‐choice oviposition bioassays were performed on each host and pathogen species with one oviposition cup containing infected larvae and the other cup containing uninfected larvae (control). Both uninfected and E. aedis‐infected female Ae. aegypti laid significantly fewer eggs in oviposition cups containing infected larvae. Uninfected gravid female Ae. albopictus and Cx. quinquefasciatus oviposited equally in cups containing uninfected larvae or containing larvae infected with V. culicis or CuniNPV, respectively. Gravid female Ae. albopictus infected with V. culicis did not display ovarian development and did not lay eggs. The decreased oviposition by gravid Ae. aegypti in containers containing E. aedis‐infected larvae may indicate that the infected larvae produce chemicals deterring oviposition.     

A recent survey of mosquito fauna in Guandong Province, southern China, with a review of past records

Abstract The southern province of Guangdong has long been subject to endemic mosquito‐borne diseases. In recent years, this region of China has experienced rapid, extensive economic development involving environmental change, making much of the scant knowledge of its mosquito fauna obsolete. This paper reviews previous mosquito surveys, some of which may be too old to be of relevance to present‐day conditions, and presents the results of a recent survey of adult and immature mosquitoes. The main vectors of mosquito‐borne diseases endemic to the area, such as dengue and Japanese encephalitis virus, develop in container habitats. A three‐year survey was carried out, between 2004 and 2006, of 4131 breeding containers in residential areas and in open, sparsely populated areas, of which approximately 50% were positive for the presence of mosquitoes, and 10 156 larvae and pupae were collected and identified. Twelve species were found in both residential and sparsely populated areas: Aedes albopictus (Skuse) (Diptera: Culicidae), Ae. lineatopennis (Ludlow), Ae. vexans (Meigen), Tanakaius togoi (Theobald), Culex barraudi Edwards, Cx dispectus Bram, Cx malayi (Leicester), Cx pallidothorax Theobald, Cx quinquefasciatus Say, Cx sitiens Wiedemann, Lutzia fuscanus Wiedemann and Tripteroides bambusa (Yamada). Armigeres subalbatus (Coquillett) was found only in containers in villages, whereas Ae. macfarlanei Edwards, Cx mimeticus Noé, Cx sinensis Theobald, Cx vegans Wiedemann, Cx wilfredi Colless and Mansonia uniformis (Theobald) were found only in non‐ or sparsely populated areas. In residential areas, the rank order of most common species, as measured by the proportion of containers colonized, was Ae. albopictus > Cx quinquefasciatus > Lu. fuscanus, whereas in sparsely populated areas the rank order was Cx quinquefasciatus > Ae. albopictus > Lu. fuscanus. Light traps in non‐ or sparsely populated areas caught 5995 adult mosquitoes of 25 species, some of which are not container breeders. The most common species were: Anopheles sinensis Wiedemann, An. maculatus Theobald, An. minimus Theobald, Ta. togoi, Cx bitaeniorhynchus Giles, Cx malayi, Cx quinquefasciatus, Cx sinensis Theobald, Cx sitiens, Cx tritaeniorhynchus Giles and Lu. fuscanus. It is noteworthy that nine species caught had not been previously recorded in Guangdong Province, highlighting the deficient knowledge of the current composition and distribution of the mosquito fauna of this part of China.     

Fine scale spatial urban land cover factors associated with adult mosquito abundance and risk in Tucson,Arizona

It is currently unclear what role microhabitat land cover plays in determining the seasonal spatial distribution of Aedes aegypti and Culex quinquefasciatus, disease vectors of dengue and West Nile Virus, respectively, in Tucson, AZ. We compared mosquito abundance to sixteen land cover variables derived from 2010 NAIP multispectral data and 2008 LiDAR height data. Mosquitoes were trapped with 30–9 traps from May to October of 2010 and 2011. Variables were extracted for five buffer zones (10–50 m radii at 10 m intervals) around trapping sites. Stepwise regression was performed to determine the best scale for observation and the influential land cover variables. The 30 m radius buffer was determined to be the best for observing the land cover‐mosquito abundance relationship. Ae. aegypti presence was positively associated with structure and medium height trees and negatively associated with bare earth; Cx. quinquefasciatus presence was positively associated with pavement and medium height trees and negatively associated with shrubs. These findings emphasize vegetation, impervious surfaces, and soil influences on mosquito presence in an urban setting. Lastly, the land cover‐mosquito abundance relationships were used to produce risk maps of seasonal presence that highlight high risk areas in Tucson, which may be useful for focusing mosquito control program actions.     

Piperonyl butoxide synergizes the larvicidal activity of Origanum vulgare essential oil and its major constituents against the larvae of Aedes albopictus and Culex pipiens quinquefasciatus

Mosquitoes bite human beings and transmit many diseases, such as malaria, dengue fever, and Zika virus. Vector control of mosquitoes is an effective strategy for reducing the spread of disease. However, extensive use of insecticides (e.g. pyrethroids and organophosphorus) has caused resistance in mosquitoes, which weakens the effectiveness of mosquito control. Phytochemicals have been considered an alternative approach to mosquito control. Essential oil (EO) was obtained from the leaves and flowers of Origanum vulgare, and its synergistic activity with piperonyl butoxide (PBO) was tested against Aedes albopictus and Culex pipiens quinquefasciatus larvae. Thirty-seven compounds were identified, among which carvacrol and thymol were two major constituents (30.73 % and 18.81 %, respectively). O. vulgare EO had a significant toxic effect against fourth-stage larvae of Cx. p. quinquefasciatus and Ae. albopictus, with LC₅₀ values of 17.51 and 75.90 mg/L. Carvacrol and thymol also each appeared to be more effective against Cx. p. quinquefasciatus (LC₅₀ = 19.30 and 11.56 mg/L, respectively) than Ae. albopictus (LC₅₀ = 26.62 and 26.66 mg/L, respectively). PBO interacted synergistically with O. vulgare EO, carvacrol and thymol with 2.60–6.26 times as much of the active compound needed without PBO as against Cx. p. quinquefasciatus and Ae. albopictus larvae. Overall, our results contribute to the development of new natural mosquito insecticides.     

Oviposition preference and offspring performance in container breeding mosquitoes: evaluating the effects of organic compounds and laboratory colonisation

1. The preference–performance hypothesis (PPH) predicts that organisms lacking parental care should oviposit in habitats that optimise offspring performance. Preference–performance relationships were investigated for the Asian tiger mosquito (Aedes albopictus Skuse) and the southern house mosquito (Culex quinquefasciatus Say) (Diptera: Culicidae), two medically important container‐breeding species, in response to an organic chemical blend mimicking decaying plant matter. Additionally, the effects of long‐term laboratory colonisation of Cx. quinquefasciatus using wild and laboratory strains were evaluated. 2. Oviposition bioassays were conducted by releasing gravid mosquitoes into field enclosures with automobile tires containing low and high concentrations of the chemical blend, and water controls. The offspring were then reared in water collected from the tires in which they were deposited. 3. Aedes albopictus and wild Cx. quinquefasciatus laid more eggs in the chemical blend than water controls but did not differentiate between the low and high concentrations. Conversely, laboratory Cx. quinquefasciatus only preferred the high concentration to the low concentration. No statistical associations between oviposition preference and larval survival were found, as the chemical blend did not affect survivorship of either species. 4. The oviposition preference for the chemical blend over water controls suggests that both species oviposit in the best available resource environment, but further studies are needed before conclusions regarding preference–performance relationships can be drawn. 5. It was found that long‐term laboratory colonisation affects the oviposition behaviour in Cx. quinquefasciatus, suggesting that behavioural studies on laboratory strains are not always applicable to wild populations.     

Spatial repellency and other effects of transfluthrin and linalool on Aedes aegypti and Aedes albopictus

In the present study, the effects of two spatial repellents (SR) were determined for Aedes aegypti and Ae albopictus, the main vectors of dengue, Chikungunya, and Zika fever. The modular high‐throughput screening system (HITSS ) was used to evaluate the response of both species to transfluthrin and linalool SR at different concentrations. The highest spatial repellency results for Ae. aegypti were obtained by transfluthrin to 0.001% with 37.50 ± 4.33%, and for linalool to 10% with 77.50 ± 3.90%. For Ae. albopictus, the highest spatial repellency percentages for transfluthrin 0.01% were 45.00 ± 3.78%, and linalool at 1% and 10% were 56.25 ± 7.06% and 56.25 ± 6.46%, respectively. Transfluthrin caused high levels of mortality with 71.25 ± 6.66%, 79.75 ± 8.65%, and 100% to Ae. aegypti and 70.00 ± 5.98% and 98.75 ± 0.82% to Aedes albopcitus. With the results of this study, we concluded that both the transfluthrin and linalool could be used as protection measures against the bite of Ae. aegypti and Ae. albopictus in the integral strategies for the control of vectors in Mexico.     

The influence of ecological factors on mosquito abundance and occurrence in Galápagos

We sampled mosquitoes across 18 sites established at different elevations and stretching from the north to the south of Isla Santa Cruz, Galápagos. Two commonly occurring species, Ae. taeniorhynchus and Cx. quinquefasciatus, were collected along with environmental variables characteristic of the trapping sites to assess their influence on mosquito abundance and occurrence in the dry season of 2015. We captured Ae. taeniorhynchus at 14 out of 18 sites and Cx. quinquefasciatus at low and high elevation sites on Santa Cruz. We utilized two generalized linear models; the first assessed the influence of environmental variables on abundances of Ae. taeniorhynchus and the second assessed the influence of these variables on the presence of Cx. quinquefasciatus. Populations of both mosquito species declined with elevation. Rainfall data were limited, as we sampled during the dry season of 2015. Distance to mangroves and maximum humidity were significant in influencing the abundance of Ae. taeniorhynchus, while maximum humidity was found to significantly influence the presence of Cx. quinquefasciatus. Both species occurred in sites where temperature, precipitation, and humidity should allow for mosquito development as well as parasitic development of the protozoan parasites that cause avian malaria. Further research involving year‐round sampling of mosquitoes and accompanying meteorological data as well as experimental studies on vector competence are required to understand disease dynamics of parasites such as avian malaria in Galápagos.     

Specific detection of the floodwater mosquitoes Aedes sticticus and Aedes vexans DNA in predatory diving beetles

Floodwater mosquitoes (Diptera: Culicidae) are associated with periodically flooded wet meadows, marshes, and swamps in floodplains of major rivers worldwide, and their larvae are abundant in the shallow parts of flooded areas. The nuisance caused by the blood‐seeking adult female mosquitoes motivates mosquito control. Larviciding with Bacillus thuringiensis israelensis is considered the most environmentally safe method. However, some concern has been raised whether aquatic predatory insects could be indirectly affected by this reduction in a potential vital prey. Top predators in the temporary wetlands in the River Dalälven floodplains are diving beetles (Coleoptera: Dytiscidae), and Aedes sticticus and Ae. vexans are the target species for mosquito control. For detailed studies on this aquatic predator–prey system, we developed a polymerase chain reaction (PCR) assay for detection of mosquito DNA in the guts of medium‐sized diving beetles. Primers were designed for amplifying short mitochondrial DNA fragments of the cytochrome C oxidase subunit I (COI) gene in Ae. sticticus and Ae. vexans, respectively. Primer specificity was confirmed and half‐life detectability of Ae. sticticus DNA in diving beetle guts was derived from a feeding and digestion experiment. The Ae. sticticus DNA within diving beetle guts was detected up to 12 h postfeeding, and half‐life detectability was estimated to 5.6 h. In addition, field caught diving beetles were screened for Ae. sticticus and Ae. vexans DNA and in 14% of the diving beetles one or both mosquito species were detected, showing that these mosquito species are utilized as food by the diving beetles.