Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters which govern them. The non-linear evolution of large scale structure produces a non-Gaussian signal which is potentially observable in galaxy shear data. We study the three-point statistics of the convergence, specifically the bispectrum, using the dark matter halo approach which describes the density field in terms of correlations between and within dark matter halos. Our approach allows us to study the effect of the mass distribution in observed fields, in particular the bias induced by the lack of rare massive halos (clusters) in observed fields. We show the convergence skewness is primarily due to rare and massive dark matter halos with skewness converging to its mean value only if halos of mass M > 10^15 M_\sun are present. This calculational method can in principle be used to correct for such a bias as well as to search for more robust statistics related to the two and three point correlations.

9 ApJ pages, 8 figures; submitted to ApJ