Studies of larval mite populations along transects, as measured with black plates, were conducted in forest and grassland habitats for a period of 67 weeks. Larvae of both Leptotrombidium (Leptotrombidium) deliense and L. (L.) fletcheri were influenced greatly by rainfall, with the larvae being abundant and easily collected during periods of heavy rainfall and difficult or impossible to collect during dry periods. Simulated rainfall maintained larval populations for longer periods during dry weather.
Mite foci were fenced above and below ground to prevent the entry of host animals and to prevent the migration of mites within the soil. Weekly counts were made over a period of thirty weeks with larvae being collected at the beginning and end of the study, but not during the intervening period of hot, dry weather. Post-larval forms can survive for long periods and mite foci can remain productive without being visited by the host animals. Mite foci may be missed by normal survey methods during hot, dry weather.