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United States Department of Agriculture

Agricultural Research Service

Research Project: BITING ARTHROPODS: INTEGRATED PEST MANAGEMENT

Location: Mosquito and Fly Research Unit

Title: Mating status and body size in Aedes albopictus (Diptera: Culicidae) affect host finding and DEET repellency

Authors
item Barnard, Donald
item Xue, Rui-De -
item Ali, Arshad -

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2012
Publication Date: N/A

Interpretive Summary: A method for protecting humans from mosquito attack and mosquito transmitted disease is to use the repellent DEET on skin. In laboratory tests of repellent efficacy, mosquito response to DEET is variable, which leads to doubt regarding the actual time protection from mosquito bites is provided. In this study, ARS scientists in Gainesville, FL and University of FL and the Anastasia Mosquito Control District scientists determined the effects of body size in mated and unmated mosquitoes on host seeking, the number of female mosquitoes that land on a human subject, and length of time DEET prevented these female from landing. The results showed that more mosquitoes were attracted to human odor than landed on a human subject and that mosquito body size and mating status caused the differences. When using DEET on skin, unmated small female mosquitoes were repelled for the longest time and large bodied mated females for the shortest time. The results show how the reliability of estimates of DEET protection time in laboratory and field repellent bioassays can be improved by testing only large bodied mated female mosquitoes.

Technical Abstract: Variations in the conditions accompanying mosquito development and mating can result in females of variable size that have not been inseminated. In this study, we compared the host finding activity of mated and unmated large and small Aedes albopictus and the repellency to these mosquitoes of 25% DEET. The percentage of females seeking the source of human odor in an olfactometer was significantly influenced by body size (P = 0.007) but not mating status (P = 0.07). Most respondents were large (71%) but 40% of all host seeking females were not inseminated. Landing rates by Ae. albopictus on human skin were influenced in screened cage tests by mating status (P <0.0001) and body size (P = 0.004). Mated females exhibited the highest landing rates (17.3% [large] and 12.7% [small]) followed by unmated large females (7.3%) and unmated small females (6.4%). The Complete Protection Time (CPT) from mosquito landing provided by 25% DEET was significantly influenced by mating status (P <0.0001) and body size (P = 0.025). Unmated small females were repelled longer (7.5 h) than unmated large females (7.0 h) and longer than small and large mated females (6.3h and 5.6 h, respectively). CPT was inversely related to mosquito landing rate in all treatment groups. The result when using 25% DEET was an average of 75 min more protection from bites by unmated females than by mated females.

Last Modified: 7/28/2014
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