Fig. 4. Maximum force output in relation to motor mass by a selection of Group 2 motors (flying insects; Marden, 1987), along with data from two studies that predicted either vastly different (microjet; Epstein et al., 2000) or subtly different (euglossine bees; Dillon and Dudley, 2004) results. These comparisons demonstrate the robustness of the M^1.0 scaling and a mean specific force of 57 N kg^-1 for these types of motors. Maximum force output (N) and motor mass (kg).