Effect of fluid viscosity on the liquid-feeding flow phenomena of a female mosquito

Abstract

SummaryLiquid-sucking phenomena by the two-pump system of a female mosquito have been investigated experimentally to understand the feeding mechanism. In most previous experimental studies on liquid-feeding insects, the net increase of mass was divided by the feeding time and fluid density to evaluate the intake rate. However, this weighting method is not so precise for mosquitoes, because they are too lightweight to measure the gain of mass accurately. In this study, the intake rate of female mosquitoes feeding various sucrose solutions was estimated using a micro particle image velocimetry technique. As the sucrose concentration increases from 1% to 50%, the intake rate decreases from 17.3 nl/s to 5.8 nl/s. Furthermore, the temporal volume variations of the two-pump chambers were estimated based on the velocity and acceleration information of the flow at the center of food canal of the proboscis. One pumping period is divided into four elementary phases, which are related to the different operational modes of the two pumps. According to the hypothetical model established in this study, the phase shift (α) between the two-pump chambers increases from 14 ms to 28 ms and the percentage of reversal flow to forward flow in a pumping period decreases 7.6% to 1.7% with increasing viscosity. The developed analytic methodology is helpful to the study of an insect’s feeding mechanism.