Behavior of RestingAedes aegypti(Culicidae: Diptera) and Its Relation to Ultra-low Volume Adulticide Efficacy in Panama City, Panama

Abstract

The resting behavior of Aedes aegypti (L.) adults was investigated in 14 districts of Panama City, Panama, in relation to ground ultra-low volume (ULV) applications of malathion. Adults primarily rested inside the premises (75.1%) at a distance Ͼ6 m from the street (86.4%). Both sexes rested mainly in bedrooms, living rooms, and bathrooms. The small ULV aerosol droplets (2Ð 4 m) penetrated all indoor resting sites of Ae. aegypti, but in low amounts. Because of the low amount of insecticide reaching the primary resting sites within the premises, limited control of the Ae. aegypti was obtained. This limited the potential effectiveness of ground vehicle ULV applied insecticide as a dengue epidemic control method.KEY WORDS Aedes aegypti, culicidae, resting behavior, ultra-low volume insecticides DURING THE 1950S and 1960s, Ͼ20 countries in the Americas were able to eradicate Aedes aegypti (L.), but in the last 20 yr, almost every one of these countries including Panama has become reinfested and has had sizable epidemics of dengue fever (Gubler and Kuno 1997). Although future outbreaks of dengue fever may be avoided by eliminating larval habitats through community participation, there are still areas with Ae. aegypti infestation that may allow outbreaks of the disease. For this reason, emergency measures must be available for use in future dengue outbreaks.The intervention used during epidemics is the ground application of small quantities of aerosol insecticide (ultra-low volume or ULV). Elsewhere, ULV applications have been shown repeatedly to give Ͻ100% control of adult Ae. aegypti populations (Hudson 1986, Focks et al. 1987, Perich et al. 1990. One reason for this reduced effectiveness is Ae. aegypti resting behavior. A portion of the population is found in wardrobes, under beds, behind furniture and in closed rooms where it is difÞcult for aerosol droplets to reach. Focks et al. (1987) hypothesized that gravid females remain sequestered during treatment periods in places that are well-protected from aerosols.Schoof (1967) indicated that the resting habits of this mosquito are relatively unknown, but suggested that adults gather at breeding places, resting there and on adjoining surfaces. In Thailand, Pant and Yasuno (1970) demonstrated that 95% of the mosquitoes rest indoors, and of these, Ͼ90% did so on surfaces that could not be sprayed with residual compounds, such as clothing, pictures, decorative objects, coverlets, and mosquito nets. This Þnding indicated that it was of little value to use residual insecticides on indoor walls. Nelson (1986) reported that mosquitoes rested indoors most frequently in bedrooms, bathrooms, and kitchens where they preferred vertical surfaces such as walls, furniture, and hanging articles such as clothing, towels, curtains, and mosquito nets, although they also were found on the ceiling and under furniture such as beds.Detailed investigation of the resting behavior of Ae. aegypti is needed if chemical control is to be adopted for the control of adult mosquitoes. In th...

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