Water balance components in adults of terrestrial red mite Balaustium sp. (Acarina: Erythraeidae)

Balaustium, spp. mites are noted for their quickness, red color, population bursts, and ubiquity. Water balance characteristics of adults were assessed to determine their primary source of water to gain insight into the biology and physiology of these poorly studied mites. Characteristics of this mite show that it is xeric adapted, featuring a 71% body water content, 39% dehydration tolerance limit, and a modest water loss rate of 2% h^-1. This species is unable to absorb water vapor from atmospheric air which is unusual for mites. This is illustrated by net water losses at water vapor activities close to saturation, failure to maintain the uptake after first day passive gains, and no detectable salt accumulation around the base of the mouthparts in scanning electron micrographs. Thus, enhanced water conservation enables this mite to withstand desiccation, and their aggressive predatory life style has apparently not necessitated evolution of an active uptake mechanism for absorption of water vapor for this mite that obtains most of its water from feeding.