This paper reports a MEMS micro force sensor with a novel configuration of differential tri-plate comb drives suitable for bulk micromachining. A high-yield fabrication process using DRIE on SOI wafers is utilized to construct the high aspect ratio devices. The sensor has a high sensitivity, good linearity, and a large bandwidth, which are required for characterizing flight behavior of fruit flies (Drosophila). The technique allows for the instantaneous measurements of flight forces, which result from a combination of aerodynamic and inertial forces generated by the wings. The potential impact of this research extends beyond gathering flight data on Drosophila melanogaster by demonstrating how MEMS technology can be used to provide valuable tools for biomechanical investigations