Walkthrough:Big Truck
"Big Truck" is a job for Sly Cooper and Murray in "Rumble Down Under" of Sly 3: Honor Among Thieves.
Walkthrough
After the cutscene, have Sly deal with the guards and activate the drill. Control will switch to Murray.
To ride the truck, hold down 
to drive forward and 
to reverse. Hitting 
while moving activates the e-brake and flips the truck over, releasing a net. Cool down the tires every once in a while by driving over scorpions or going into the water.
After capturing 8 red solider scorpions, Bentley will say that less scorpions are coming to the surface. Control will switch to Sly. Climb up to the top of the drill and activate it. Control will switch to Murray.
Repeat the process for the remaining 12 red scorpions. The water has drained down, though, so squish scorpions (including the blue worker ones) to cool your tires.
Once you capture all 20 red scorpions, set them loose in the mine, and it's Job Complete.