Larval development of Muellerius cf. capillaris in small (1st-year juveniles, shell diameter 0.96 +/- 0.05 cm) and medium-size (2nd-year juveniles, 1.27 +/- 0.06 cm) Trochoidea seetzenii land snails was significantly more rapid than in large adult snails (1.96 +/- 0.09 cm). Only 9% of the inoculated 1st-stage larvae (400 +/- 20 per snail) were recovered from the large snails as compared to 25% from the medium and small snails. Of the exposed small snails, however, only 35% survived to the end of the experiment (33 days post-infection) as compared to a 97.5% and 98% survival rates for the same period in the medium and large adult snails, respectively.