The Hexug Spider's motors are controlled by a motor controller on the small circuit board. The chip is the ST1155A and the datasheet can be downloaded here: ST1155A Datasheet
In the picture above, pin 1 is the bottom left by the dot. The pins are then numbered counter clockwise from 1 to 14. The control pins are 2,6 and 9,13. The easiest way to hack this is to remove the MCU on the opposite side then tack small 28 or 32 gauge wires to the pins of the 1155. Do not use any more solder than necessary to tack the wires down or you will end up with solder bridges.