Comparison of the correlation between Einstein radii and lensing cross sections for a sample of isolated triaxial dark matter haloes to the same correlation for a sample of merging triaxial dark matter haloes. The red solid line in the left (right) diagram indicates the best linear fit relation between median (effective) Einstein radii and lensing cross sections found for a sample of triaxial dark matter haloes at redshift z_l = 0.5. The blue crosses represent selected pairs of Einstein radii and lensing cross sections during cluster mergers (see text for details).