Effects of temperature and relative humidity on development and survival of the free-living stages of Trichostrongylus colubriformis, T. rugatus and T. vitrinus.

Temperatures of 4 and 10 degrees C reduced the rate of hatching of eggs and the development of the pre-infective stages of T. colubriformis and T. rugatus, but not T. vitrinus. Eggs of T. rugatus hatched at 4 degrees C, but did not develop to the infective stage. At 20 and 30 degrees C, no differences were detected between species in egg hatching or the development of infective larvae. Third-stage larvae of T. rugatus survived for significantly longer periods of time at 33 and 56% relative humidities at a temperature of 20 degrees C than did either T. colubriformis or T. vitrinus. At 30 degrees C, differences were less marked, but T. rugatus and T. colubriformis survived longer than T. vitrinus. The results are discussed in relationship to the known distribution of these species in eastern Australia.