High temperature and dehydration tolerance of the red velvet mite, Balaustium sp. (Erythraeidae), permit the exploitation of extremely hot, dry microhabitats

Abstract

Red velvet mites Balaustium sp. nr. putmani, a mite commonly associated with landscaping projects throughout the Midwestern United States, show a particular affinity for warm, sunny locations. Adults display a remarkable tolerance for high temperature, capable of actively crawling on extremely hot surfaces for extended periods. To determine the upper thermal tolerance of this mite, we compared short-term 1-hour heat-shock responses, coupled with a behavioural scoring system, among all mobile instars (larva, deutonymph and adult) that occur on hot surfaces. Maximum heat shock for 50% survival was 48°C for larvae, 52°C for deutonymphs and 52–54°C for adults, which is high for an acarine and indicates that the active instars of this mite are generally resistant to heat stress. Larvae experienced their first major drop in survival of ≥20% between 42°C and 44°C; this drop occurred at 48–50°C for deutonymphs and 50–52°C for adults. A distinguishing feature of deutonymphs and adults is their ability to recover from heat-induced injury, something that larvae apparently lack. This recovery is characterized by an abrupt injury/mortality at 52°C (nearly all survive heat shocks of 40–48°C) for adults and deutonymphs, whereas the response in larvae is graded following a dose–response from 42°C to 50°C. Our conclusion is that enhanced high-temperature tolerance coincides with heat-shock recovery in deutonymphs and adults that are active for longer periods of time during the hottest periods each year. The larval season occurs early during the cooler spring, which facilitates the establishment of populations. Balaustium sp. nr. putmani requires a dry habitat to function properly. It seems reasonable to suggest that sunny sites create ideal dry habitats for B. sp. nr. putmani to thrive, and increased sun exposure at these preferred dry sites simultaneously requires that these mites are heat tolerant.

Keywords:

• Parasitengona
• high-temperature tolerance
• heat
• larva
• deutonymph
• adult