Weft inserting and withdrawing grippers for a shuttleless weaving machine are disclosed, wherein the weft inserting gripper has a clamping member composed of pivoting blade-type foot biased by a spring and mounted in such a way that the foot bears against a horizontal gripping surface at an angle nearly equal to the complementary of the angle of friction between the yarn and the gripping surface. The gripping member of the withdrawing gripper has a hook with a wedge which can be axially slid towards and away from the hook to seize and hold the thread, or to clear it. The axial sliding motion of the wedge is controlled by a linkage which is resiliently biased by a spring.