Mortality and length of development of B. eburneus nauplii is modified in laboratory culture by both temperature and concentration of unicellular algal food. At 20 and 25 degree C mean larval survival was 63.5% and 66.0%, respectively, at an algal concentration of 1 x 10 super(5) cells ml super(-1). When the algal concentration was doubled to 2 x 10 super(5) cells ml super(-1) mean survival increased significantly to 92.5 and 96.5% at 20 and 25 degree C, respectively (p = 0.002 at both temperatures). At 30 degree C the difference in mortality related to algal food concentration disappeared and mean survival was above 90% at both concentrations. Over the interval of 20 to 30 degree C, time to complete development to the cyprid stage decreased from a median of 7.6 to 3.9 d at 2 x 10 super(5) cells ml super(-1) and from 10.8 to 3.9 d at the lower food level of 1 x 10 super(5) cells ml super(-1). At 30 degree C there was no difference between the 2 food concentrations in the median time to reach the cyprid stage.