Host-seeking nymphal Amblyomma americanum (L.) (Acari: Ixodidae) were placed into heated water, and their survival or their torpidity was recorded as a function of exposure time. Exposures were determined that either kill the nymphs or affect their mobility. All nymphs died when exposed for a minute or more to a temperature >51 degrees C. Nearly all nymphs remained motionless for a period of time when exposed for 3 min to a temperature >44 degrees C.