A surgical instrument, comprising: a housing; a shaft extending distally from the housing; an ultrasonic waveguide extending through the shaft; and an end effector assembly (60; 600), including: a first jaw member (61; 610) defining an insulative tissue-contacting surface and first and second electrically-conductive tissue-contacting surfaces disposed on either side of the insulative tissue-contacting surface, the first and second electrically-conductive tissue-contacting surfaces adapted to connect to a source of electrosurgical energy; and a second jaw member (62; 620) including an ultrasonic blade body adapted to receive ultrasonic energy from the ultrasonic waveguide and positioned to oppose the insulative tissue-contacting surface of the first jaw member, wherein the first jaw member is movable relative to the second jaw member between a spaced-apart position and an approximated position to apply a first grasping force to tissue disposed between the first and second jaw members; wherein a slider is slidably disposed on an outer distal end of the shaft and coupled to an actuator operably associated with the housing and selectively actuatable to move the slider between a retracted position and an extended position, characterised by the slider being movable, independent of the movement of the first jaw member from the spaced-apart position to the approximated position, between the retracted position, wherein the slider is disposed proximally of the first and second jaw members, and the extended position, wherein the slider extends about the exterior of the first jaw member and is configured to urge the first jaw member from the approximated position further towards the second jaw member to apply a second, greater grasping force to tissue disposed between the first and second jaw members. a housing; a shaft extending distally from the housing; an ultrasonic waveguide extending through the shaft; and an end effector assembly (60; 600), including: a first jaw member (61; 610) defining an insulative tissue-contacting surface and first and second electrically-conductive tissue-contacting surfaces disposed on either side of the insulative tissue-contacting surface, the first and second electrically-conductive tissue-contacting surfaces adapted to connect to a source of electrosurgical energy; and a second jaw member (62; 620) including an ultrasonic blade body adapted to receive ultrasonic energy from the ultrasonic waveguide and positioned to oppose the insulative tissue-contacting surface of the first jaw member, wherein the first jaw member is movable relative to the second jaw member between a spaced-apart position and an approximated position to apply a first grasping force to tissue disposed between the first and second jaw members; wherein a slider is slidably disposed on an outer distal end of the shaft and coupled to an actuator operably associated with the housing and selectively actuatable to move the slider between a retracted position and an extended position, characterised by the slider being movable, independent of the movement of the first jaw member from the spaced-apart position to the approximated position, between the retracted position, wherein the slider is disposed proximally of the first and second jaw members, and the extended position, wherein the slider extends about the exterior of the first jaw member and is configured to urge the first jaw member from the approximated position further towards the second jaw member to apply a second, greater grasping force to tissue disposed between the first and second jaw members. a first jaw member (61; 610) defining an insulative tissue-contacting surface and first and second electrically-conductive tissue-contacting surfaces disposed on either side of the insulative tissue-contacting surface, the first and second electrically-conductive tissue-contacting surfaces adapted to connect to a source of electrosurgical energy; and a second jaw member (62; 620) including an ultrasonic blade body adapted to receive ultrasonic energy from the ultrasonic waveguide and positioned to oppose the insulative tissue-contacting surface of the first jaw member, wherein the first jaw member is movable relative to the second jaw member between a spaced-apart position and an approximated position to apply a first grasping force to tissue disposed between the first and second jaw members; wherein a slider is slidably disposed on an outer distal end of the shaft and coupled to an actuator operably associated with the housing and selectively actuatable to move the slider between a retracted position and an extended position, characterised by the slider being movable, independent of the movement of the first jaw member from the spaced-apart position to the approximated position, between the retracted position, wherein the slider is disposed proximally of the first and second jaw members, and the extended position, wherein the slider extends about the exterior of the first jaw member and is configured to urge the first jaw member from the approximated position further towards the second jaw member to apply a second, greater grasping force to tissue disposed between the first and second jaw members.