SURVIVAL AND WATER-BALANCE CHARACTERISTICS OF UNFED ADULT AMBLYOMMA CAJENNENSE (ACARI, IXODIDAE)

Off-host survival, water balance, and cold tolerance of unfed adult, C ayenne ticks, Amblyomma cajennense (F.), were examined to evaluate spe cies characteristics important to zoogeography and off-host ecology. S urvivorship decreased when males and females were subjected to progres sively drier constant environmental conditions. Average maximum surviv al was 641.2 and 682.5 d at 85% RH and 23 degrees C (2.98 mm Hg) for m ales and females, respectively. Mean survival in both sexes was progre ssively less variable in drier conditions. Slopes of log-linear models of survival days based on saturation deficit (mm Hg) were significant ly different between males and females at 50%, but not at 25 or 0%. Wh ole-body water loss rates for 4-wk-old adults were measured at 0% RH a nd 23 degrees C until ticks became nonambulatory. The mean whole-body water loss rate of females, 0.06128% h(-1), was 11.3% less than for ma les, 0.06914% h(-1). Although nonambulatory ticks appeared dead, >1/2 of the individuals from each sex regained ambulatory status after they were removed from 0% RH and exposed to 96% RH for 24 h. Among these, male ticks averaged 0.44 more recuperative (ambulatory) cycles than fe males, although, the duration encompassing all recuperative cycles was generally lone;er for females and on average, females gained 8.16% mo re weight than males upon each rehydration. Estimates of the mean crit ical equilibrium activity for males and females were 0.74 av and 0.79 av, respectively. A. cajennense adults were found to be less tolerant to -12.5 degrees C than adult lone star ticks, Amblyomma americanum (L .), whose distribution encompasses more temperate regions. Although A. cajennense exhibit little host preference and are capable of extended off-host survival, the establishment of populations beyond this speci es zoogeographic distribution may be constrained by an intolerance to cold.