Effects of temperature and relative humidity on development times and mortality of eggs from laboratory and wild populations of the European house-dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae).

As part of a study on passive physical control of house-dust mites, a total of 6000 eggs from a population of Dermatophagoides pteronyssinus (Trouessart, 1897) from 17-year-old laboratory cultures were incubated at 60 temperature and relative humidity combinations between 10-35 degrees C and 55-100% RH. Eggs hatched at every combination, although mortality and development time increased between 10-20 degrees C and 30-35 degrees C and below 65% RH. Optimum conditions were 35 degrees C and 80-85% RH. In temperate dry conditions, eggs from a wild population were found to be more resistant to mortality: they developed faster, with 7 times lower mortality than eggs from the laboratory population. This may have been because the laboratory population had become acclimated to the constant near-optimum conditions at which it was kept. Therefore it has been suggested that where laboratory cultures have been used in studies relating to passive physical control, caution should be taken in applying the conclusions to wild populations in the natural house-dust environment.