Calibration and evaluation of field cage for oviposition study with Aedes (Stegomyia) aegypti female (L.) (Diptera: Culicidae)

Abstract

-Differences among results gathered from insect behavior studies conducted in laboratory and fi eld situations are due to ambient variables that differ greatly between both environments. In laboratory studies the environmental conditions can be controlled whereas in fi eld temperature, humidity and air velocity vary uncontrollably. The objective of this study was to calibrate and evaluate an experimental area (fi eld cage) (14 x 7 x 3.5 m) subdivided into eight test cages (2.5 x 2.5 x 2 m) for use in behavioral oviposition tests of Aedes aegypti (L.) mosquitoes for developing a new methodology to assess attractants and oviposition traps. Test cage calibration involved: (1) minimal experiment duration tests; (2) optimal female release number per traps test and (3) trap placement tests. All tests used gravid A. aegypti females; 3-4 days post blood meal and the sticky trap MosquiTRAP ® to catch adults. Ninety percent of the females released were recaptured 2h after the beginning of the experiment, and this allowed up to 32 test repetitions/day to be conducted in the fi eld cage. The minimum number of females necessary to conduct statistical analyses was 20 females/trap/test per cage. No signifi cant difference was found in the behavioral response of gravid females to four different trap positions within test cages. Field trapping results with attractant were similar to those in the fi eld cage. Therefore, the fi eld cage could replace fi eld trapping for evaluating at least mosquito traps and oviposition attractants for A. aegypti.KEY WORDS: Oviposition behavior, attractant, semi-fi eld, MosquiTRAP RESUMO -Discrepâncias entre resultados de estudos de comportamento de insetos em laboratório e em campo ocorrem devido a variáveis encontradas entre os ambientes. Enquanto em laboratório as condições são controladas, em campo os insetos são avaliados em condições variáveis de temperatura, umidade e velocidade do ar. O objetivo deste trabalho foi calibrar e avaliar uma área experimental (14 x 7 x 3,5 m) contendo oito gaiolas de teste (2,5 x 2,5 x 2 m), para estudos comportamentais de oviposição para Aedes aegypti (L.) visando desenvolver uma nova metodologia para avaliar atraentes e armadilhas de oviposição em semi-campo. A calibração consistiu na (1) determinação do tempo de realização dos experimentos e no (2) número de fêmeas liberadas por teste e na (3) avaliação das posições das armadilhas no interior das gaiolas de teste. Fêmeas de A. aegypti de 3-4 dias após repasto sangüíneo e MosquiTRAP ® foram utilizadas nos experimentos. Noventa por cento das fêmeas liberadas foram recapturadas após 2h do início dos experimentos, permitindo a realização de até 32 repetições/dia. A amostra mínima de fêmeas por experimento para a realização de análises estatísticas foi limitada a 20 fêmeas/armadilha/gaiola. Não foi observada diferença na resposta comportamental das fêmeas nas diferentes posições avaliadas. Resultados com MosquiTRAP em área urbana foram semelhantes aos do semi-campo. Portanto, a metodologia pode substitui...

Influence of breeding site availability on the oviposition behaviour of Aedes aegypti

“…In laboratory conditions, four transparent acrylic boxes (150 × 50 × 41 cm) were kept in a room with monitored temperature and humidity conditions (27 ± 3°C, 60-90% RH) and a photoperiod of 12L:12D ( Eiras & Jepson 1991 ). The semi-field tests were performed in an experimental area of 14.0 × 7.0 × 3.5 m, where eight cages (2.5 × 2.5 × 2.0 m each) were installed ( Roque & Eiras 2008) . The temperature, RH and the photoperiod ranged according to the external environment and were monitored with a Thermo-Hygrometer.…”

“…The temperature, RH and the photoperiod ranged according to the external environment and were monitored with a Thermo-Hygrometer. The tests were considered valid only when the temperature reached a minimum of 25°C ( Roque & Eiras 2008) .…”

Olfaction in vector-host interactions

“…Semi-field cages are considered a controlled environment that offers intermediate conditions between the laboratory and the field for behavioural studies, where both laboratory and wild-caught insects can be tested. Behavioural studies in semi-field cages (Roque and Eiras 2008) showed that the MosquiTRAP baited with a formulation of synthetic oviposition cues caught similar proportions of gravid Ae. aegypti to traps baited with infusions of 10-45 days of fermentation (Figure 3).…”

Ovitraps Provide a Reliable Estimate of Wolbachia Frequency during wMelBr Strain Deployment in a Geographically Isolated Aedes aegypti Population

“…aegypti females have a behavior called skip oviposition, in which mosquitoes lay their eggs in different breeding sites to avoid intraspecific competition [36,37]. Previous studies conducted under semi-field conditions revealed that females could lay their eggs in four to six ovitraps distributed over a 2.5 × 2.5 × 2.0 m cage [38]. In fact, one of the available breeding sites (with ovitraps varying in numbers between 2, 4, 8, and 16 per cage) was consistently found to yield more than 40% of eggs [39].…”