Mosquitocidal activities of Chenopodium botrys whole plant n-hexane extract against Culex quinquefasciatus / Atividades mosquitocidas do extrato de n-hexano de planta inteira de Chenopodium botrys contra Culex quinquefasciatus

This research aimed to investigate various mosquitocidal activities of Chenopodium botrys whole- plant n-hexane extract against Culex quinquefasciatus. The extract showed remarkable larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus. During the larvicidal and pupicidal activities, the 24-hour lethal concentration (LC50) of extract against 2nd instar larvae, 4th instar larvae and pupae were 324.6, 495.6 and 950.8 ppm, respectively. During the CDC (Centers for Disease Control and Prevention) bottle bioassay for adulticidal activity, the median knockdown times (KDT50) at 1.25% concentration was 123.4 minutes. During the filter paper impregnation bioassay for adulticidal activity, the KDT50 value at 0.138 mg/cm2 concentration was 48.6 minutes. The extract was fractionated into 14 fractions through silica gel column chromatography which were then combined into six fractions on the basis of similar retention factor (Rf) value. These fractions were screened for adulticidal activity by applying CDC bottle bioassay. The fraction obtained through 60:40 to 50:50% n-hexanes-chloroform mobile phase with 0.5 Rf value showed 100% adulticidal activity at 0.2% concentration. During oviposition deterrent activity, the highest concentration (1000 ppm) showed 71.3 ± 4.4% effective repellence and 0.6 ± 0.1 oviposition activity index. During adult emergence inhibition activity, the median emergence inhibition (EI50) value was 312.3 ppm. From the outcome of the present investigation, it is concluded that the n-hexane extract of C. botrys whole- plant possesses strong larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus.

Esta pesquisa teve como objetivo investigar várias atividades mosquitocidas do extrato n-hexano de planta inteira de Chenopodium botrys contra Culex quinquefasciatus. O extrato mostrou atividades larvicida, pupicida, adulticida, dissuasora de oviposição e inibidora da emergência de adultos contra a Cx. quinquefasciatus. Durante as atividades larvicida e pupicida, a concentração letal de 24 horas (CL50) do extrato contra larvas de 2º estádio, larvas de 4º estádio e pupa foi de 324,6, 495,6 e 950,8 ppm, respectivamente. Durante o bioensaio com frasco do CDC (Centros para Controle e Prevenção de Doenças) para adulticida, o tempo médio de desativação (KDT50) na concentração de 1,25% foi de 123,4 minutos. Durante o bioensaio de impregnação com papel de filtro para a atividade adulticida do extrato, o valor KDT50 na concentração de 0,138 mg / cm2 foi de 48,6 minutos. O extrato foi fracionado em 14 frações através de cromatografia em coluna de gel de sílica que foram então combinadas em seis frações com base em um valor de fator de retenção (Rf) semelhante. Essas frações foram selecionadas quanto à atividade adulticida por meio da aplicação do bioensaio com garrafa do CDC. A fração obtida através da fase móvel de n-hexanos-clorofórmio 60:40% a 50:50% com valor de 0,5 Rf apresentou atividade adulticida de 100% na concentração de 0,2%. Durante a atividade de dissuasão da oviposição, a maior concentração de extrato (1000 ppm) apresentou repelência efetiva de 71,3 ± 4,4% e índice de atividade de oviposição de 0,6 ± 0,1. Durante a atividade de inibição da emergência de adultos, o valor médio de inibição da emergência (EI50) foi de 312,3 ppm. A partir do resultado da presente investigação, conclui-se que o extrato de n-hexano da planta inteira de C. botrys possui fortes atividades larvicida, pupicida, adulticida, dissuasora da oviposição e inibidora da emergência de adultos contra a Cx. quinquefasciatus.

Effects of Peganum harmala L Seed Extract on Culex pipiens (Diptera: Culicidae) / Efeitos do extrato de semente de Peganum harmala L em Culex pipiens (Diptera: Culicidae)

Mosquito-borne diseases result in the loss of life and economy, primarily in subtropical and tropical countries, and the emerging resistance to insecticides is increasing this threat. Botanical insecticides are promising substitutes for synthetic insecticides. This study evaluated the larvicidal and growth index of Culex pipiens of four solvent extracts of Terminalia chebula, Aloe perryi, and Peganum harmala against Cx. pipiens. None of the 12 extracts exhibited larvicidal potential against third instars except the ethyl acetate extract of P. harmala. After 24 h of exposure, the LC50 value was 314.88 ppm, and the LC90 value was 464.19 ppm. At 320 ppm, the hatchability was 25.83%, and it resulted in 100% mortality. In addition, the eggs treated with the EtOAc extract of P. Harmala exhibited a long larval period compared with the control. The larval period continued for 12 days, and the pupal period took three days in the treatment groups. The growth index data also exhibited a decrease (0.00–7.53) in the treated groups compare with 8.5 in the control. The transformation of eggs into adults decreased with increasing concentrations. This paper is the first report on the development and growth index of Cx. pipiens potential using P. harmala seeds.

As doenças transmitidas por mosquitos resultam na perda de vidas e economia, principalmente em países subtropicais e tropicais, e a resistência emergente aos inseticidas está aumentando essa ameaça. Os inseticidas botânicos são substitutos promissores dos inseticidas sintéticos. Este estudo avaliou o índice larvicida e de crescimento de Culex pipiens de quatro extratos solventes de Terminalia chebula, Aloe perryi e Peganum harmala contra Cx. pipiens. Nenhum dos 12 extratos exibiu potencial larvicida contra o terceiro ínstar, exceto o extrato de acetato de etila de P. harmala. Após 24 horas de exposição, o valor LC50 era 314,88 ppm e o valor LC90 era 464,19 ppm. A 320 ppm, a eclodibilidade foi de 25,83% e resultou em 100% de mortalidade. Além disso, os ovos tratados com o extrato de EtOAc de P. harmala exibiram um longo período larval em comparação com o controle. O período larval continuou por 12 dias, e o período pupal durou três dias nos grupos de tratamento. Os dados do índice de crescimento também exibiram uma diminuição (0,00-7,53) nos grupos tratados em comparação com 8,5 no controle. A transformação de ovos em adultos diminuiu com o aumento das concentrações. Este artigo é o primeiro relatório sobre o índice de desenvolvimento e crescimento de Cx. potencial de pipiens usando sementes de P. harmala.

Ensayos de sensibilidad de larvas de Aedes aegypti y Culex quinquefasciatus frente al nematodo Heterorhabditis bacteriophora en condiciones de laboratorio / Laboratory susceptibility tests of Aedes aegypti and Culex quinquefasciatus larvae to the entomopathogenic nematode Heterorhabditis bacteriophora

Resumen Introducción. Aedes aegypti es el vector de los virus del dengue, la fiebre amarilla, el Zika y el chikungunya, y Culex quinquefasciatus, de los virus de la encefalitis de Saint Louis y de la del Oeste del Nilo. Objetivo. Evaluar la capacidad infecciosa de Heterorhabditis bacteriophora N4 en larvas de C. quinquefasciatus y A. aegypti en el laboratorio. Materiales y métodos. Treinta larvas de segundo estadio de cada especie de mosquito se expusieron a diferentes dosis (0:1, 1:1, 5:1, 15:1, 100:1, 500:1, 750:1 y 1.500:1) de ejemplares juveniles infectivos del nematodo. Se hicieron cuatro réplicas por dosis. Resultados. El parasitismo varió entre 2,5 y 80 % en C. quinquefasciatus y entre 4,2 y 92,5 % en A. aegypti, con diferencias significativas entre las dosis (p<0,0001). Las DL50 fueron de 160,8 ejemplares juveniles infectivos por larva de C. quinquefasciatus y 113,6 por larva de A. aegypti; 4 a 6 % de los ejemplares juveniles infectivos llegaron a la fase adulta en C. quinquefasciatus, y 12 a 61 % en A. aegypti. Nuevos ejemplares juveniles infectivos aparecieron a partir de la dosis de 100:1. En A. aegypti aparecieron solo con dosis superiores a esta y, en C. quinquefasciatus, con una dosis de 1500:1. Se observó melanización de los ejemplares juveniles infectivos en las dos especies de mosquitos. Conclusión. Se estableció la sensibilidad de estas especies de mosquitos al parasitismo producido por un aislamiento autóctono de H. bacteriophora en condiciones de laboratorio y su potencial efecto como agente de control biológico.

Abstract Introduction: Aedes aegypti is the vector of dengue, yellow fever, Zika and Chikungunya viruses, and Culex quinquefasciatus is the vector of St. Louis and West Nile encephalitis viruses. Objective: To evaluate infectivity of Heterorhabditis bacteriophora N4 in C. quinquefasciatus and A. aegypti larvae under laboratory conditions. Materials and methods: Thirty second-instar larvae of the two mosquito species were exposed each to different doses (0:1, 1:1, 5:1, 15:1, 100:1, 500:1, 750:1 and 1,500:1) of nematode infective juveniles. Four replications per dose were performed. Results: Parasitism varied between 2.5 and 80 % in C. quinquefasciatus, and between 4.2 and 92.5 % in A. aegypti, with significant differences between doses (p<0.0001). DL50 were: 160.8 infective juveniles per larva for C. quinquefasciatus and 113.6 infective juveniles per larva for A. aegypti. In C. quinquefasciatus, 4 to 6 % of the infective juveniles developed to adults and in A. aegypti, 12- 61 %. In A. aegypti the emergence of new infective juveniles occurred with 100:1, 500:1, 750:1 and 1,500:1 infective juveniles per larva, and in C. quinquefasciatus, with 1,500:1 infective juveniles per larva. Melanization of infective juveniles was observed in both mosquito species. Conclusion: The susceptibility of these mosquito species to parasitism of an indigenous isolate of H. bacteriophora in the laboratory was demonstrated. Heterorhabditis bacteriophora N4 could be an efficient biological control agent.

Aceites esenciales y sus componentes como una alternativa en el control de mosquitos vectores de enfermedades / Essential oils and their components as an alternative in the control of mosquito vectors of disease

Resumen Más de la mitad de la población humana está expuesta a contraer infecciones transmitidas por mosquitos. El cambio climático y la aparición de cepas resistentes a los insecticidas tradicionalmente utilizados han motivado la búsqueda de nuevos agentes capaces de controlar las poblaciones de mosquitos. Los aceites esenciales han resultado ser eficaces agentes repelentes y larvicidas. El objetivo de este trabajo fue revisar las investigaciones llevadas a cabo en los últimos años sobre la actividad larvicida de los aceites esenciales y sus componentes contra mosquitos de los géneros Aedes, Anopheles y Culex, así como los últimos reportes sobre su posible mecanismo de acción.

Abstract More than half of the human population is exposed to mosquito-borne infections. Climate change and the emergence of strains resistant to traditionally used insecticides have motivated the search of new agents for mosquito population control. Essential oils have been effective repellents and larvicidal agents. The aim of this work was to review research studies conducted in recent years on the larvicidal activity of essential oils and their components against Aedes, Anopheles and Culex mosquitoes, as well as the latest reports about their possible mechanism of action.

Distribution of the members of the Pipiens Assemblage in the sympatric area from Argentina: which is where and when?

Given their medical and veterinary relevance, the members of the Pipiens Assemblage are a worldwide target of ecological research. The distribution of Culex pipiens s.s. and Cx. quinquefasciatus converge in Buenos Aires, Argentina, where hybrids have been detected. Each member of the assemblage exhibits a distinct eco-physiological behaviour that can affect its efficiency in pathogen transmission. Our aim was to identify the environmental drivers for the spatio-temporal distribution of each member, focusing on latitudinal and urbanisation gradients. Immatures of mosquitoes were surveyed in artificial containers found within 11 public cemeteries, raised up to the adult stage and identified by their male genitalia. The distribution of each member was associated with the environment in a Generalized Linear Model. The variable accounting for most of the heterogeneity was latitude; Cx. quinquefasciatus was collected more frequently at northern cemeteries, whereas Cx. pipiens and hybrids were more likely at the southern extreme. The urbanisation gradient was also associated with the occurrence of Cx. quinquefasciatus and hybrids at the high and low end, respectively. Other relevant variables were cemetery total area, the proportion with graves and the presence of plastic flowers in the containers. The spatial distribution of the members of the Pipiens Assemblage within the sympatric region in South America is driven by environmental features. The information presented herein provides essential baseline data for surveillance programs and control activities.

Characterisation of Culex quinquefasciatus (Diptera: Culicidae) larval habitats at ground level and temporal fluctuations of larval abundance in Córdoba, Argentina

The aims of this study were to characterise the ground-level larval habitats of the mosquito Culex quinquefasciatus, to determine the relationships between habitat characteristics and larval abundance and to examine seasonal larval-stage variations in Córdoba city. Every two weeks for two years, 15 larval habitats (natural and artificial water bodies, including shallow wells, drains, retention ponds, canals and ditches) were visited and sampled for larval mosquitoes. Data regarding the water depth, temperature and pH, permanence, the presence of aquatic vegetation and the density of collected mosquito larvae were recorded. Data on the average air temperatures and accumulated precipitation during the 15 days prior to each sampling date were also obtained. Cx. quinquefasciatus larvae were collected throughout the study period and were generally most abundant in the summer season. Generalised linear mixed models indicated the average air temperature and presence of dicotyledonous aquatic vegetation as variables that served as important predictors of larval densities. Additionally, permanent breeding sites supported high larval densities. In Córdoba city and possibly in other highly populated cities at the same latitude with the same environmental conditions, control programs should focus on permanent larval habitats with aquatic vegetation during the early spring, when the Cx. quinquefasciatus population begins to increase.

Temperature Effects on the Immature Development Time of Culex eduardoi Casal & García (Diptera: Culicidae)

The effect of constant temperatures on the development time from first instar to adult emergence was studied in Culex eduardoi Casal & García reared at 7, 10, 15, 20, 25, 30 or 33°C. Data were adjusted to the linear degree-day model and the nonlinear Briére model. According to the linear model, the development time was inversely related to the rearing temperatures between 7°C and 25°C. Maximum mortality (100 percent) was recorded at temperatures > 30°C. According to the linear model, the development threshold temperature and thermal constant were 5.7°C and 188.8 degree days, respectively. The lower and upper threshold temperatures and the optimum temperature for the nonlinear model were -2.3, 30.0 and 28.1°C, respectively.

Hábito alimentar de Aedes aegypti e Culex quinquefasciatus e sua implicação na capacidade reprodutiva / Feeding habits of Aedes aegypti and Culex quinquefasciatus and its implications on the reproductive capacity

O estudo de hábito alimentar de espécies vetoras de doenças, ou potencialmente vetoras, indica os organismos envolvidos na transmissão e manutenção das doenças. Com a expansão de áreas urbanas e consequente aglomeração humana, como acontece no município de Marília, criou-se ambiente propício para a criação de mosquitos adaptados à essa situação. Esse trabalho teve por objetivo caracterizar o hábito alimentar de culicídeos capturados em área urbana do município de Marília e relacionar com o nível socioeconâmico. A técnica utilizada para a identificação do hábito alimentar foi o ELISA (Enzyme Linked Immunosorbent Assay) considerando quatro hospedeiros (humano, cão, ave e roedor). Entre as espécies coletadas com maior frequência estavam os Aedes aegypti e Culex quinquefasciatus. Em laboratório foram testados os aspectos da capacidade reprodutiva para fêmeas dessas espécies, alimentadas artificialmente com sangue dos mesmos hospedeiros observados em campo. As espécies coexistem em toda a área mesmo em diferentes níveis socioeconâmicos. A não concorrência pode ser explicada por apresentarem perfis hematofágicos distintos. Diferentemente do Ae. aegypti, o Cx. quinquefasciatus é espécie eclética quanto as fontes de hematofagia, no entanto apresentou maior frequência de repastos sanguíneos em roedores. Os Ae. aegypti se mostraram essencialmente antropofílicos.

Efficacy of pirimiphos-methyl (50% EC), as a larvicide for the control of Culex quinquefasciatus.

Background & objectives: Pirimiphos-methyl, an organophosphorus insecticide is known to overcome resistance mechanisms of mosquitoes to other organophosphates. Information on the duration of efficacy of pirimiphos-methyl (50% emulsifiable concentrate) for the control of immatures of Culex quinquefasciatus, the vector of bancroftian filariasis, is scanty and hence site specific field trials are necessary to determine the field dosage. Pirimiphos-methyl (50% EC) was tested for its efficacy in cesspits and drains against the immatures of Cx. quinquefasciatus at Puducherry, an endemic area for filariasis, south India. Methods: In cesspits, Pirimiphos-methyl (50% EC) was tested at the dosage of 25, 50, 100 and 200 g(ai)/ ha and in drains at 50, 100 and 200 g(ai)/ha. Immature density during pre-treatment and post-treatment periods was recorded and the efficacy was determined by calculating percentage reduction in larval and pupal densities for a period of about one month. Results: In cesspits, application of the insecticide at 25 and 50 g(ai)/ha reduced the density of larvae by >80 per cent for 2-4 days only, whereas at 100 and 200 g(ai)/ha, the efficacy lasted for 7-8 days. More than 80 per cent reduction was observed in pupal density for 4 days at 50 g(ai)/ha and for 10-12 days at 100 and 200 g(ai)/ha respectively. In drains treated with 50 g (ai)/ha, >80 per cent reduction in larval density was recorded up to 3rd day post-treatment. The efficacy showing >80 per cent reduction in larval density lasted for 12-13 days and the same in pupal density lasted for 10-12 days at 100 and 200 g(ai)/ha. Interpretation & conclusions: At the dosages of 100 and 200 g(ai)/ha, pirimiphos-methyl (50% EC) showed no difference in the control of larvae of Cx. quinquefasciatus in cesspits and drains. Pirimiphosmethyl may be applied at the field dosage of 100 g (ai)/ha at 10 day-intervals in the larval habitats of Cx. quinquefasciatus to achieve >80 per cent reduction in immature density.

Mosquito fauna [Diptera: culicidae] and seasonal activity in Makka al Mukarramah region, Saudi Arabia

From March 2004 to February 2006, a mosquito survey was conducted in Makka Al Mukarrama Region, in the western part of Saudi Arabia, and 19 species which belong to 4 genera, were collected: Aedes [2 species], Anopheles [8 species], Culex [8 species] and Culiseta [1 species]. The mosquitoes were Aedes caspius, Ae. aegypti, Anopheles d'thali, An. gambiae, An. multicolor, An. rhodesiensis, An. sergenti, An. stephensi, An. subpictus, An. turkhudi, Culex arbieeni, Cx. laticinctus, Cx. pipiens, Cx. quinquefasciatus, Cx. sinaiticus, Cx. tigripes, Cx. tritaeniorhynchus, Cx. univittatus and Culiseta longiareolata. Cx. arbieeni was reported for the first time in Saudi Arabia from Al Taif District. The physical properties of water of mosquito's larval breeding sites showed the total dissolved salts [TDS] varied between 70-15552 ppm, pH ranged between 5.4-11.2 and water temperature varied between 15°C in winter to 40.7°C in summer. There was no correlation between these physical properties and the distribution of mosquito larvae. Light traps collected 1858 mosquitoes, and adult Culex were the most prevalent as 1658 [89.24%] were collected, followed by 121 [6.51%] Aedes, 68 [3.66%] Anopheles and 11 [0.59%] Culiseta. The effects of temperature and rainfall on seasonal abundance of mosquitoes in the study area are discussed

Prevalence of mosquito species in Chhura block of Raipur district of Chhattisgarh state.

Mosquitoes act as vectors for several diseases including malaria and filaria. In Indian scenario, Chhattisgarh is endemic for both the diseases. The present study on prevalence of mosquito population in block Chhura of Raipur district of Chhattisgarh state was undertaken between August 2002 and March 2004 to asses the distribution pattern of various species of mosquitoes and their seasonal variations. Indoor resting mosquitoes were collected from five villages by aspirator tube in the morning (06:00-08:00 hr) using torchlight. Adult mosquitoes were identified using standard morphological and pictorial keys. Altogether 11 species belonging to three genera viz., Anopheles (7 species), Armigeres (1 species) and Culex (3 species) were recorded during study period. Average man-hour mosquito density was high in February 2003 (62.15) & March 2003 (69.35) and declined gradually till June 2003. From July 2003, it started rising again and reached a peak in August (94.10)-September (91.60) 2003. The vector species i.e. Anopheles culicifacies and Anopheles annularis were recorded high in rainy and winter seasons.

Evaluación del nicho ecológico deformas larvales de Aedes aegypti y Culex quinquefasciatus (Díptera: Culicidae) en una comunidad urbana de San José, Costa Rica / Evaluation of the ecological niche of Aedes aegpti and Culex quinquefasciatus (Díptera: Culicidae) larvae in an urban community of San José, Costa Rica

Observations related to the width and overlap of the ecological niche for larval forms of Aedes aegypti and Culex quinquefasciatus in artificial containers were performed using the data obtained during two laval surveys in the four sectors of the neighborhood 'La Carpio', San Jose, Costa Rica. 'La Carpio' was the first community of the Metropolitan Area of San José that suffered a dengue outbreak. The first survey was performed in the dry season of 2003 and the second one in the wet season of the same year. The width of niche was expressed using the Levin Index, and the overlap of niche was determined by the Morisita Index modified by Horn. In both larval surveys Ae. aegypti and Cx. quinquefasciatus were present. Ae. aegypti showed higher values for width of niche in the four sectors of the neighborhood and during both surveys.During the first larval survey (dry season of 2003), there was an overlap of niche only in sectors I and 3. In the wet season, the overlap was observed in the four sectors, but the values were higher in sectors I and 2. Results show that Ae. aegypti is the most common species of mosquitoes in artificial containers in the neighborhood, and that the role of Cx. quinquefasciatus as modulator of the Ae. aegypti populations could be limited.

Se realizaron observaciones relativas a la amplitud y solapamiento del nicho ecológico para las formas larvales de Aedes aegypti y Culex quinquefasciatus en contenedores artificiales, utilizando datos obtenidos in dos encuestas larvales que se ejecutaron en los cuatro sectores que conforman el poblado 'La Carpió', San José, Costa Rica. 'La Carpió' fue la primer comunidad del Área Metropolitana de San José en sufrir un brote de dengue. La primera encuesta tuvo lugar en la estación seca del 2003 y la segunda se realizó en la estación lluviosa del mismo a +/- o. La amplitud de nicho fue expresada por medio del índice de Levin y el solapamiento de nicho fue calculado mediante el índice de Morisita modificado por Horn. En ambas encuestas Ae. aegypti y Cx. quinquefasciatus estuvieron presentes. Ae. aegypti mostró los valores más elevados en lo referente a amplitud de nicho en los cuatro sectores de la comunidad durante ambas estaciones. En la primer encuesta larval (estación seca del 2003), hubo solapamiento de nicho sólo en los sectores 1 y 3. En la estacón lluviosa el solapamiento fue observado en los cuatro sectores, pero los valores más elevados se dieron en los sectores 1 y 2. Los resultados muestran que Ae. aegypti es el mosquito más abundante en contenedores artificiales en la comunidad y el papel de Cx. quinquefasciatus como modulador de las poblaciones parece ser limitado.

Aspectos da distribuição de Culex (Culex) quinquefasciatus Say (Diptera, Culicidae) na região do rio Pinheiros, na cidade de São Paulo, Estado de São Paulo, Brasil / Aspects of the distribution of Culex (Culex) quinquefasciatus Say (Diptera, Culicidae) in the region of the Pinheiros River, in the city of São Paulo, State of São Paulo, Brazil

A distribuição de Culex (Culex) quinquefasciatus Say (1823) ao longo das margens do rio Pinheiros e os principais fatores que levam à proliferação da espécie foram estudados efetuando-se coletas semanais de mosquitos adultos, no período de um ano, em três pontos eqüidistantes às margens do rio. Para as coletas de mosquitos utilizou-se aspirador à bateria, por um período de cinco minutos. Os mosquitos foram identificados, diferenciados segundo o sexo e contados. Para verificação do estado fisiológico, as fêmeas foram separadas em vazias, com sangue e com ovos. Foram coletados 35.684 mosquitos, todos identificados como Cx. quinquefasciatus, sendo 39,4 por cento fêmeas e 60,6 por cento machos. As freqüências tomaram proporções diferentes entre os pontos de coletas e, em uma série temporal. O ambiente impactado do rio Pinheiros representa um excelente criadouro de Cx. quinquefasciatus, confirmado pela ocorrência de picos acentuados na freqüência de mosquitos, com desenvolvimento de forma explosiva e sobreposições entre as gerações, após as chuvas e em épocas de verão.

The distribution of Culex (Culex) quinquefasciatus Say (1823) along of the margins of the Pinheiros river and the main factors that lead to the proliferation of the species were studied doing weekly collections of adult mosquitoes, in the period of one year, in three equidistant points in the margins of the river. For the collections of mosquitoes battery vacuum cleaner was used, for a period of five minutes. The mosquitoes were identified, differentiated according to the sex and counted. For verification of the physiological state, the females were differentiated in empty, with blood or eggs. A total of 35.684 mosquitoes were captured, all of them were identified as Cx. quinquefasciatus, being 39.4 percent females and 60.6 percent males. The frequencies took different proportions between the points of collections and in a temporary series. The damaged environment of the Pinheiros river represents an excellent breeding site of Cx. quinquefasciatus, confirmed by the occurrence of picks accentuated in the frequency of mosquitoes, with development in an explosive way and accumulation between the generations, after the rains and in summer times.

Role of some factors on the breeding of JE vector Culex vishnui group.

Vector of JE, Culex vishnui group, prefer to breed in rice field. During the present study, roles of some factors like irrigation, manuring, pesticide application, rainfall, temperature and pH of the breeding water, depth of breeding water and height of paddy plants on breeding of Culex vishnui group larvae have been studied. It is evident from the study that besides striking role of the factors like manuring and pesticide application, other factors have also some role on the breeding of JE vectors at their breeding sites.

Ciclo de vida de Culex quinquefasciatus Say, 1826 (Diptera Culicidae) bajo condiciones no controladas en Bogotá / Life cycle of Culex quinquefasciatus Say (Diptera: Culicidae) under uncontrolled conditions

El objetivo de este trabajo fue estudiar varios aspectos del crecimiento y el desarrollo de los estadios inmaduros de Culex quinquefasciatus Say, 1826 (Diptera: Culicidae), especie antropofílica frecuentemente encontrada en Bogotá. Con este fin, se realizaron dos experimentos en diferentes épocas del año 2001 (enero-febrero y septiembre-octubre), bajo condiciones no controladas (luz, temperatura y humedad relativa). Se colocaron recipientes plásticos transparentes con agua de charca a la que se le adicionó concentrado para perro; se tomaron cuatro balsas al azar para estudiar el ciclo de vida utilizando los parámetros de la tabla de vida: mortalidad y supervivencia. Las hembras ovipositaron entre cinco y ocho días después de la ingestión de sangre. El número de huevos por balsa varió entre 152 y 203. La eclosión de larvas L1 fue de 50 por ciento en el primer experimento y de 75 por ciento en el segundo. Se destacó la naturaleza no sincrónica de la eclosión de las L1, la menor duración proporcional del estadio de pupa (11 por ciento del tiempo del desarrollo total) y la eficiencia del cambio pupa-adulto (98,61 por ciento). Se reporta una menor duración del ciclo de lo informado previamente. Además, los altos porcentajes de eclosión (83,58 por ciento), pupación (86,63 por ciento) y emergencia (98,61 por ciento) con las condiciones presentes para estos experimentos (temperatura media 14,8°C y 15,1°C y humedad relativa del 72,5 por ciento y 74,1 por ciento, respectivamente) indican el alto grado de adaptación de C. quinquefasciatus al ambiente bogotano. Estas características, más la capacidad vectorial y la resistencia a los insecticidas, hacen de esta especie un problema de salud pública

Predatory potential of Nepa cinerea against mosquito larvae in laboratory conditions.

Biocontrol potential of nepidae bug, Nepa cinerea against immature stages of Anopheles stephensi, Anopheles culicifacies, Culex quinquefasciatus and Aedes aegypti was studied under laboratory conditions. It was found that N. cinerea had the highest predation against An. stephensi followed by An. culicifacies, Cmx quinquefasciatus and Ae. aegypti. From the analysis, it was found that N. cinerea has good predation efficacy. It can be used as a biological control agent to control of mosquito breeding in integrated disease vector control programme.

Cuscuta hyalina Roth., an insect development inhibitor against common house mosquito Culex quinquefasciatus Say.

A preliminary screening of crude acetone extract of Cuscuta hyalina Roth. was conducted against the laboratory reared preadult stages of common house mosquito Culex quinquefasciatus (Say) (Diptera: Culicidae). 24 h LC50 of third and fourth instar larvae and pupae were 303 ppm, 306.44 ppm and 97.66 ppm respectively. The extract completely restrained the adult mosquito emergence at sublethal doses (50 ppm for third instar and 75 ppm for fourth instar), by disrupting the normal morphogenesis. The extract was found to be an effective oviposition deterrent at 80 ppm. The plant was also found to be effective in suppressing the adult emergence when directly sprinkled as dry powder on the water surface.

Description of immature stages of Culex ocossa Dyar & Knab, Culex delpontei Duret and Culex pereyrai Duret of the Melanoconion subgenus (Diptera: Culicidae)

The larva and pupa of Culex (Melanoconion) ocossa Dyar & Knab are redescribed and those of Culex (Melanoconion) delpontei Duret and Culex (Melanoconion) pereyrai Duret are described from specimens collected in the states of Säo Paulo and Paraná, Brazil. The pupa of Cx. ocossa differs from those of the other two species in having seta 5-IV-VI dark with strongly aciculated branches, and caudolateral angle of segment VIII produced into sharp point, and seta 1-P present; Cx. delpontei can be distinguished from Cx. pereyrai in possessing paddle lightly tanned, trumpet flared, and wing and leg cases lightly tanned, without pattern of dark spots; Cx. pereyrai can be recognized by having wing case with pattern of dark, discontinuously pigmented, longitudinal lines, and trumpet cylindrical, not flared. The larvae of the three species share the presence of seta 2-C placed medially to seta 1-C