Over a period of 20 months the survival time of the non-parasitic stages of the cattle tick was investigated under simulated field conditions at three locations near Port Moresby. The work was begun in a year with favourable conditions for larval survival and continued into a less favourable year. Egg-laying and hatching occurred throughout the period of investigation and showed little fluctuation, but larval survival varied with the location and the season. The mean survival time in open tussock, shaded tussock and sheltered tube respectively was, 14.1, 13.5 and 15.6 weeks at Kila Kila, 13.3, 15.1 and 18.0 weeks at Tiaba and 14.8, 17.5 and 24.7 weeks at Bisianumu. Under the conditions prevailing in the Port Moresby area, maximum temperature is the most important factor controlling the survival of larvae. The bulk of a larval population lives for over two-thirds of a total exposure time; once larvae begin to die the majority are dead within a few weeks, but a small number remain alive for some time longer.