Natural history of a Balaustium sp. (Parasitengona: Erythraeidae) from eastern North America, with emphasis on moisture and temperature requirements

Abstract

ABSTRACTXeric-suitability and heat tolerance by having a low water loss rate (3%/h) and high upper lethal temperature (48°C) are reported for adults of a Balaustium sp., which match typical hot, dry Balaustium habitat where pollen and arthropod prey on landscape plants are available. They do not have the capacity for water vapour absorption; i.e. the critical equilibrium humidity ≥100% relative humidity with body water losses in unsaturated air. They drink water from droplets, occurring only on occasion and by chance. Prey is their primary source of water. This mite has several features: (1) the inability to recover from heat shock, (2) little heat shock resistance, and (3) no acclimatizing effects by conditioning at a sublethal temperature. In absence of a heat stress-survival mechanism, cooler, shady refuges are sought and used more often that simultaneously help to minimize desiccation risks. This selection for shady spots permits niche differentiation from the bright-red B. murorum, a more desiccation- and heat-resistant species, that coexists in the same habitat and is active in well-lit, sunny locations.