Ld652Y cells from the gypsy moth, Lymantria dispar, are highly sensitive to apoptotic stimuli compared to BM-N cells from the silkworm, Bombyx mori, and undergo apoptosis upon infection with various nucleopolyhedroviruses (NPVs). We previously cloned and characterized Dronc homologues from L. dispar Ld652Y and B. mori BM-N cells and demonstrated that L. dispar Dronc (Ld-Dronc) undergoes proteolytic processing more rapidly and extensively than does B. mori Dronc (Bm-Dronc) upon infection with vAcΔp35, a p35-defective Autographa californica multiple NPV. Here, we comparatively examined expression and proteolytic processing of the Ld- and Bm-Dronc proteins in the transient expression assays using three different insect cell lines, Ld652Y, BM-N and Spodoptera frugiperda Sf9. We demonstrate that even in the transient expression assays, Ld-Dronc undergoes proteolytic processing and activates caspase-3-like protease more rapidly and extensively than Bm-Dronc in a cell-line independent manner. These results indicate that intrinsic properties of Dronc are involved in the differing capacity of Ld652Y and BM-N cells to induce apoptosis in response to apoptotic stimuli, including NPV infection.