Larvae of Ischnura verticalis reared on either green or brown substrates showed significant differences in colour; larval colour tended to match that of the substrate. When presented with different-coloured substrates, both green and brown animals chose brown in preference to green. Preference for brown was not significantly altered by the presence of fish. Green larvae on green substrates were at significantly greater risk to predation by fish than they were on brown substrates. In addition, green larvae on brown substrates captured significantly more larval mayflies (Callibaetis sp.) than did green larvae on green substrates. Results suggest that the adaptive significance of colour change and choice of substrates is related to both avoidance of predators and concealment from potential prey.