Within- and between-treatment relationships between mean reproductive parasite loads, latency time and virulence. Each circle represents the mean for a single parasite selection line, averaged over three replicate assay tubes. Black circles denote selection lines from early-killing, open circles selection lines from late-killing treatments. Regression lines illustrate correlations within treatments. Squares indicate the treatment means, averaged over selection line means. Error bars represent standard error. Parasite load = number of reproductive forms per infected individual on day 7; latency time = time until 50% of infected hosts produce infectious forms; virulence = Log-transformed host density uninfected minus log-transformed host density infected in the individual assay (i.e., larger positive values indicate higher virulence).