Kinetics of water exchange between a mite, Laelaps echidnina, and the surrounding air

The temporal dependence of water exchange between an arthropod and its surroundings fits a mathematical model based on diffusion theory. The model requires that the mass change rate of L. echidnina results from a zeroorder component consisting primarily of water sorption and a first-order component made up largely of water loss. Tentatively, transpiration of water is associated with primarily the tracheal system, and sorption of water primarily with other surfaces. Placing mites in a CO 2 atmosphere greatly increased their water loss, but had little effect on sorption of water. The effect of increase in temperature on the sorption rate ( m ̇ s ) and transpiration rate constant ( k T ) was to increase them. The influence of the activity of the water in the vapour phase in the ambient air ( a v ) was primarily on sorption.