The ladybug uses two motors from a salvaged hobby servos from which the gears were broken. It does not use any gearbox at all, but relies on the small wheels to have a decent speed. I have to say that this approach works and is also used in some commercial (toy) robot kits (velleman running bug). The only drawback I had was the relative high power consumption of the servo motors. The choice of the batteries was limited due to the small size of the body. I had to settle with some non-chargeable button batteries to power the electronics and some AAAA batteries (rather small) for the two motors.
The brains are (again) a AT90S2313 from Atmel, running at 10Mhz, the motor driver is a L293D, a dual H-bridge with build-in clamp diodes.
» That’s all