模拟降水对朱砂叶螨实验种群数量的干扰作用

采用人工模拟降雨的方法研究了降水对棉花苗期朱砂叶螨校正虫口减退率的影响以及转移干扰作用,评价棉花苗期降水对朱砂叶螨种群数量的控制作用。结果表明,暴雨(49.59%±3.09%)、大雨(33.21%±2.46%)、中雨(37.25%±0.986%)和小雨(36.03%±2.69%)均能明显降低朱砂叶螨的校正虫口减退率,其中暴雨对朱砂叶螨校正虫口减退率的影响极为明显,显著高于大雨、中雨和小雨。而大雨、中雨和小雨对朱砂叶螨校正虫口减退率的影响两两之间无显著差异。随着降水量逐步增加,对朱砂叶螨数量由释放点向叶片正面和叶柄位置转移的干扰作用逐步增强。在释放点之间,大雨、中雨和小雨均对朱砂叶螨转移干扰作用不明显,但暴雨对朱砂叶螨转移干扰作用极为明显。     

The effect of inbreeding and larval feeding regime on immature development of Aedes albopictus

The fundamental approach to the biological control of Aedes albopictus requires the mass rearing of mosquitoes and the release of highly competitive adults in the field. As the fitness of adults is highly dependent on the development of immatures, we aimed to identify the minimum feeding regime required to produce viable and competitive adults by evaluating three response parameters: development duration, immature mortality, and adult wing length. Our study suggests at least 0.60 mg/larva/day of larval diet composed of dog food, dried beef liver, yeast, and milk powder in a weight ratio of 2:1:1:1 is required to maximize adult fitness. With standardized protocols in mass rearing, intensive studies can be readily conducted on mosquito colonies to facilitate comparisons across laboratories. This study also evaluated the differences in response of laboratory and field strains under different feeding regimes. We found that strain alone did not exert substantial effects on all response parameters. However, the field strain exhibited significantly lower immature mortality than the laboratory strain under the minimum feeding regime. Females and males of the laboratory strain had longer wing lengths under nutritional constraint due to the higher mortality that resulted in reduced interactions with the remaining larvae. Meanwhile, the field strain exhibited heterogeneous duration of immature development compared with the laboratory strain. The disparities demonstrated by the two strains in this study suggest the effect of inbreeding surfaced after a long term of laboratory colonization. Despite the trade‐offs resulting from laboratory colonization, the competitiveness of the laboratory strain of Ae. albopictus is comparable to the field strain, provided the larvae are fed optimally.     

Oviposition by Aedes aegypti and Aedes albopictus: Influence of congeners and of oviposition site characteristics

We investigated the oviposition behavior of Ae. aegypti and Ae. albopictus. In particular we examined whether small‐scale site characteristics and the presence of conspecifics or congeners altered oviposition by these mosquitoes. Various combinations of females of the two species were allowed to oviposit inside cages among either vegetation (potted plants) or structural components (wood and concrete blocks). Numbers of eggs deposited per female were compared between species, sides, and treatments. Most significant differences between treatments and species involved differences between single species and mixed species treatments. Ae. aegypti deposited more eggs/female in the vegetation side than in the structure side whereas the opposite pattern was evident for Ae. albopictus. Ae. aegypti females had higher frequency of skip oviposition than Ae. albopictus. An average of 63% of the containers in the two‐species treatments contained eggs of both species, with more frequent joint occurrences observed in the treatment with three females of each species than in the treatments with one of each. Our results point to the existence of various interactions between gravid Ae. aegypti and Ae. albopictus females at or near the oviposition sites but further experimental work is necessary to fully characterize the interactions and their specific mechanisms.     

Synthesis and bio-evaluation of aryl hydrazono esters for oviposition responses in Aedes albopictus

A novel series of aryl hydrazono esters (AHE) (1-13) were synthesized (yield 76-98%) to study the oviposition responses in Aedes albopictus (Skuse) mosquitoes for the first time. At a concentration of 10 μg ml⁻¹ in dual choice experiment, among the screened compounds, AHE-12 showed remarkable oviposition attractant activity with an oviposition activity index (OAI) of +0.299 (greater than 95% confidence limit) comparable to p-cresol (OAI +0.320) which is well-reported oviposition attractant for Aedes aegypti. Conversely, AHE-10 exhibited highest oviposition deterrent activity with OAI −0.247. The possible utilization of these compounds will be in integrated vector management strategies.     

Influence of Bacillus thuringiensis var. israelensis on oviposition of Aedes albopictus (Skuse).

The effect of Bacillus thuringiensis var israelensis (B.t.i.) on the oviposition behavior of Aedes albopictus was evaluated in the field and laboratory in Clemson, SC, U.S.A. In the field, water taken from containers in which mosquito larvae were reared (conditioned water) was placed in 16 containers. Eight containers received 50 jld of B.t.i., and eight with water only were kept as controls. In the laboratory, field-collected females of Ae. albopictus were placed in rearing chambers and provided two containers for oviposition, one with 50 microl of B.t.i and one a control with water only. Eight cage experiments were conducted, five using filtered tap water and three with conditioned water. In the field over the 13 trials, more eggs were laid in the containers with B.t.i. although no significant difference was found in the number of eggs between the treatment and controls over 72 h. In the laboratory, more eggs were laid in the containers with B.t.i. versus the controls. The containers had filtered tap water and B.t.i. had significantly more eggs laid in them compared to the controls.     

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.     

Laboratory and field evaluation of insect repellents as oviposition deterrents against the mosquito Aedes albopictus

Three experimental approaches were used to evaluate the oviposition deterrency of three insect repellents, AI3-35765, AI3-37220 (piperidine compounds), and the standard N,N-diethyl-3-methylbenzamide (deet) to the mosquito Aedes albopictus Skuse (Diptera: Culicidae). Against laboratory-reared Ae. albopictus gravid females, the EC50 values of AI3-37220, AI3-35765 and deet were 0.004%, 0.008% and 0.011% in laboratory cages and 0.004%, 0.01% and 0.009% in an outdoor screened cage. For a natural population of Ae. albopictus tested in the field, the EC50 values were determined as 0.004%, 0.008% and 0.001%, respectively. Ageing concentrations of 0.1% of each repellent provided >50% effective oviposition deterrency against the laboratory population of Ae. albopictus for 13 days in laboratory cages, for 15 days in the outdoor cage, and for 21 days against field population of Ae. albopictus in Florida. These topical skin repellents are effective oviposition deterrents for Ae. albopictus when employed at relatively low application rates.     

The effect of rainfall on population dynamics in Sahara-Sahel rodents

In arid and semi-arid regions, rainfall is scarce, limiting primary productivity and animal reproduction. As long-term population monitoring is limited in remote arid areas, indirect and remote technicals are needed. We investigated if and how populations of rodents in Sahara-Sahel responded to past events of rainfall. Using short field surveys and remotely sensed rainfall data, spanning between years 2010 to 2015, we tested if rainfall prior to field surveys affected populations of Gerbillus rodents. Generalized additive analysis showed that amount of moonlight (the effect of number of days away from full moon) negatively correlated with number of trapped animals. When controlling for moonlight and geographic and temporal variation, rainfall up to 1 year prior to surveys positively and rainfall 2 years prior to surveys negatively correlated with number of trapped gerbils. We suggest that the effect of increased number of gerbils resulted from reproduction and population density increase after bursts of primary productivity. Negative correlation with rainfall could be related to increased predation or other ecological effects (e.g., resource collapse, pathogens spread) on prey population densities and activity levels. Our results suggest multiphase delayed effect of gerbils population response to rainfall implying interactive model of population regulation in rodent communities on Sahara-Sahel. Presented indirect method and results are readily applicable to population monitoring and management of remote and understudied areas.     

Adaptation of the BG-Sentinel trap to capture male and female Aedes albopictus mosquitoes

In recent years, the remarkable spread of Aedes albopictus (Skuse) (Diptera: Culicidae) throughout the world has drawn attention to this hitherto poorly studied species, particularly after its role in outbreaks of chikungunya fever in the western Indian Ocean and in Italy. Variants of sterile insect technique (SIT), including the release of transgenic males with a dominant lethal gene (RIDL), have been proposed in the search for new and innovative methods of control. Knowledge of male dispersal, mating behaviour and longevity will be critical to the success of this approach. We present an effective and practical method for trapping both male and female Ae. albopictus using a mouse-baited BG-Sentinel trap.     

Evaluation of attractants and egg-laying substrate preference for oviposition by Aedes albopictus (Diptera: Culicidae).

Evaluation of oviposition attractants and substrate preferences of Aedes albopictus was carried out under laboratory and field conditions. To obtain candidate oviposition substances we used a water rinse of 3 mollusk species: blood cockle (Anadara granosa), carpet shell (Paphia undulata), and sea mussel (Mytilus smaragdinus), and the giant tiger prawn (Penaeus monodon). The rinse water of carpet shell and giant tiger prawn showed higher attractiveness for ovipostion than the other candidate attractants. The filter paper substrate received fewer eggs than the other two substrates. There was no significant difference between the mean number of eggs laid on hardboard paddles and sponge sheets. The hatching rate of Ae. albopictus eggs laid on hardboard paddles was higher than those from the filter papers and sponge sheets. The sponge had lethal effects on Ae. albopictus eggs, and very few eggs laid on sponge hatched. In field experiments, evaluation of attractiveness of carpet shell rinse in ovitraps lined with sponge sheet as egg-laying substrate was carried out in various habitats and different areas of Thailand. The mean number of eggs in traps containing carpet shell rinse was significantly higher than those laid in rainwater traps. These studies reveal that the carpet shell and giant tiger prawn rinses are sources of oviposition attractant for Ae. albopictus under both laboratory and field conditions and could possibly be used as an attractant in surveillance and control.     

First finding of Dirofilaria repens in a natural population of Aedes albopictus

The invasive mosquito Aedes albopictus (Skuse) (Diptera: Culicidae) has become widespread in Italy during the past decade. Also Italy has foci of canine filariasis caused by Dirofilaria (Spirurida: Onchocercidae), due to subcutaneous D. repens Railliet & Henry as well as the dog heartworm D. immitis (Leidy) transmitted by various vector mosquitoes (Diptera: Culicidae). In 2002, at Fiumicino, west of Rome (Lazio Region), 17% of dogs were found to have D. repens microfilariae in peripheral blood. To evaluate the role of Ae. albopictus as a vector of Dirofilaria in this area, female mosquitoes were collected daily, June-October 2002, landing on dog or human bait in a rural house at Focene. Mosquitoes were maintained at 27 degrees C and 70% RH for 6 days, to allow development or purging of filaria larvae, then identified and frozen for subsequent molecular assay with filaria-specific ribosomal S2-S16 primers. To distinguish specimens harbouring infective L3 Dirofilaria larvae, DNA was extracted separately from the mosquito abdomen and head-thorax. Dirofilaria species were identified by sequencing, confirmed by polymerase chain reaction of positive specimens using primers specific for D. immitis and D. repens. Dirofilaria DNA was detected in 3/154 (2%) of Ae. albopictus females examined: D. repens DNA in head-thorax and abdomen of one collected 27th July; D. immitis in the abdomen of one collected 24th September; DNA of both D. immitis and D. repens in the head-thorax of one collected 11th October 2002. Thus Ae. albopictus is a potential vector of both Dirofilarias in Italy, representing risks for veterinary and human health.     

Forest canopy,water level,and biopesticide interact to determine oviposition habitat selection in Aedes albopictus

Understanding how interacting abiotic and biotic factors influence colonization rates into different habitat types is critical for both conserving and controlling species. For example, the rapid global spread of Asian tiger mosquitoes, Aedes albopictus, has reduced native species abundances and produced disease outbreaks. Fortunately, bacterial endospores of two Bacillus species (biospesticide) are highly lethal to Ae. albopictus larvae and have been commercially developed to reduce populations. Oviposition habitat selection is the first defense Ae. albopictus females possess against any control substance added to breeding sites, and considerable variation exists in their response to biopesticides. In a field experiment, I crossed the presence/absence of biopesticides, with two canopy (open, closed) and water (high, low) levels at 64 breeding sites, to examine if these interacted to influence oviposition site choice. Avoidance of biopesticide was most pronounced in closed canopy sites and those with low water levels, as all main effects and two‐way interactions influenced oviposition. Oviposition habitat selection represents a possible mechanism of resistance to biopesticides and other methods used to kill mosquito larvae. Future experiments examining how larval density and mortality modify these results should allow for more effective control of this highly invasive species.     

Effects of forced egg-retention in Aedes albopictus on adult survival and reproduction following application of DEET as an oviposition deterrent.

The insect repellent DEET (0.1% concentration), used as a mosquito oviposition deterrent in the laboratory, influenced the retention and maintenance of mature eggs by caged gravid female Aedes albopictus Skuse. This egg-retention mechanism could benefit survival because the gravid females were ultimately able to lay maintained eggs upon availability of water, but the length of forced egg-retention time reduced the number of eggs laid per female. Gravid females with retained eggs also laid a higher percentage of eggs that failed to tan, and this percentage increased with time duration of egg-retention. Percent egg hatch was not significantly affected by DEET when used as an oviposition deterrent; however, percent hatch was affected by time duration of egg-retention in both treated (exposed to DEET) and untreated (control) gravid females. The rate of egg hatch was considerably reduced after three weeks of retention; this reduction declined to zero for treated and control females at six and four weeks post-treatment, respectively. The fecundity and fertility of gravid female Ae. albopictus were affected by the time duration of forced egg-retention.     

Temperature and photoperiod effects on dormancy status and life cycle parameters in Aedes albopictus and Aedes aegypti from subtropical Argentina

Aedes albopictus (Diptera: Culicidae) distribution is bounded to a subtropical area in Argentina, while Aedes aegypti (Diptera: Culicidae) covers both temperate and subtropical regions. We assessed thermal and photoperiod conditions on dormancy status, development time and mortality for these species from subtropical Argentina. Short days (8 light : 16 dark) significantly increased larval development time for both species, an effect previously linked to diapause incidence. Aedes albopictus showed higher mortality than Ae. aegypti at 16 °C under long day treatments (16 light : 8 dark), which could indicate a lower tolerance to a sudden temperature decrease during the summer season. Aedes albopictus showed a slightly higher percentage of dormant eggs from females exposed to a short day, relative to previous research in Brazilian populations. Since we employed more hours of darkness, this could suggest a relationship between day‐length and dormancy intensity. Interestingly, local Ae. aegypti presented dormancy similar to Ae. albopictus, in accordance with temperate populations. The minimum dormancy in Ae. albopictus would not be sufficient to extend its bounded distribution. We believe that these findings represent a novel contribution to current knowledge about the ecophysiology of Ae. albopictus and Ae. aegypti, two species with great epidemiological relevance in this subtropical region.     

Aedes albopictus (Diptera: Culicidae) oviposition response to organic infusions from common flora of suburban Florida

We evaluated the oviposition response of gravid Aedes albopictus (Skuse) to six organic infusions. Laboratory and field‐placed oviposition cups baited with water oak (Quercus nigra L.), longleaf pine (Pinus palustris P. Mill), or St. Augustine grass (Stenotaphrum secundatum (Walt.) Kuntze), as well as binary infusion mixtures of each, were used. In addition, a triple‐cage, dual port olfactometer was used to measure upwind response of gravid individuals to these infusions. We found that Ae. albopictus deposited more eggs in infusion‐baited cups compared with water alone. Moreover, significantly more eggs were laid in the water oak and a water oak‐pine mixture as compared with the St. Augustine grass infusion in laboratory bioassays. However, a negative upwind response was observed with longleaf pine infusion in the olfactometer. In field cages, significantly more eggs were deposited in infusion‐baited cups as compared with water alone and a greater percentage of eggs were deposited in cups containing a water oak and the water oak‐longleaf pine mixture as compared with cups containing single infusions or their mixtures.     

Utilization of larval and pupal detritus by Aedes aegypti and Aedes albopictus

The utilization of detritus sources by mosquito larvae during development may significantly affect adult life history traits and mosquito population growth. Many studies have shown invertebrate carcasses to be an important detritus source in larval habitats, but little is known regarding how invertebrate carcasses are utilized by mosquito larvae. We conducted two studies to investigate the rate of detritus consumption and its effect on larval development and life history traits. Overall, we found that Aedes aegypti and Aedes albopictus larvae rapidly consumed larval detritus, while pupal detritus was consumed at a significantly slower rate. We also found that the consumption of larval detritus significantly increased larval survivorship and decreased male development time but did not significantly influence female development time or pupal cephalothorax length for either sex. Our results suggest that the direct consumption of larval detritus can support the production of adults in larval habitats that lack allochthonous detritus inputs or where such organic inputs are insufficient. These studies indicate that different forms of invertebrate detritus are utilized in distinct ways by mosquito larvae, and therefore different forms of invertebrate detritus may have distinct effects on larval development and adult life history traits.     

白纹伊蚊和埃及伊蚊经卵传递登革病毒的研究

白纹伊蚊和埃及伊蚊通过吸食病毒液或叮吸有病毒血症的小鸡血后,能感染登革１－４型病毒,并能在蚊体内增殖,对感染雌蚊了１和子２代幼虫,雌性或雄性成虫４５５９只,分１０１批进行了病毒检测,白纹伊蚊子１代的批阳性率;登革１型为１０％（１／１０）２型为２２．２２％（２／９）３型为３３．３３％（４／１２）,４型为２８．９５％（１１／３８）登革１～４型的最低子代感染率依次主国０．２０％,０．７１％,０．７０％和