Proliferation of red velvet mite Balaustium sp. nr. putmani (Erythraeidae) in Ohio based on water relations of active instars

Abstract

ABSTRACT Population bursts, numbering in thousands of individuals, are characteristic of red velvet mites, Balaustium sp. nr. putmani, in the springtime in Central Ohio. We determined water-balance characteristics for each of the mobile instars (larva, deutonymph, adult female; males are seemingly absent from this population) to link dehydration tolerance with heightened activity in the same habitat. This mite loses water rapidly: larva > deutonymph > adult. None of these active instars could absorb water vapor, unlike many terrestrial mites, indicating that this mite must imbibe liquid as free water or from food sources to maintain water balance. As a voracious predator, most of the liquid is probably obtained from feeding. Developmentally, larvae are the most sensitive and vulnerable to water stress because of their high net transpiration rate and low dehydration tolerance limit. Additionally, urnulae glands are only present in the post-larval instars; hence, larvae lack the protective waterproofing secretion that is provided by these glands. Deutonymphs and adults are much more resistant to desiccation, are capable of losing approximately 40% of their water content before succumbing to death, and have reduced water loss rates. We concluded that population bursts of B. sp. nr. putmani might be a response to abundance of plant pests in the landscape. Deutonymphs and adults are modified for water conservation and are correspondingly active for longer periods of time. Larvae survive for a brief time, which minimizes their exposure to desiccating habitats, and use the cooler temperatures experienced early in the season, which suppress their high rate of water loss.