THE EFFECTS OF TEMPERATURE AND WATER-VAPOR ACTIVITY ON WATER-LOSS BY VARROA-JACOBSONI (ACARI, VARROIDAE)

The effect of temperature and relative humidity on the water mass (and survival) of adult female Varroa jacobsoni was studied. This hemolymp h-feeding ectoparasite of the honey bee, Apis spp. was exposed to thre e temperatures (20, 30, 34 degrees C) and five water vapor activities of 0, 0.60, 0.75, 0.85, 0.97 a(v) (water vapor activity (a(v)) is equa l to % RH/100). Water loss was greatest at a high temperature and low a(V). Time to reach 50% mass at Oa(v), which is a reflection of whole body water loss, was 16+/-1.8, 5+/-0.4, and 5+/-0.5 hs at 20,30, and 3 4 degrees C, respectively. At 0.97a(V) for each significant temperatur e, we saw a 2-4 fold increase in time to lose 50% body mass. The most interesting observation was the impact of having mites at 0.85 versus 0.97a(v) (20 degrees C), where time to reach 50% increased from 35+/-3 .9 to 123+/-22 hs. These results suggest a contribution by metabolic a nd/or active water vapor uptake. The values at 0.60, 0.75, and 0.85 a( v) were statistically similar at 20 and 30 degrees C. At each level of a(v), significantly faster moisture loss occurred at 30 and 34 degree s C than at 20 degrees C, but they (30 and 34 degrees C) were not sign ificantly different from each other.