Outdoor Wonders you should get out more ...

Google

One day in the Lingayen Gulf area of the Philippines, I saw a small troupe of boys carrying these bamboo tubes, carefully scanning the ground.

The device is a simple tube of bamboo, with one joint left intact to form a cover. There are two notches cut into the bamboo. The top notch holds a small bamboo trigger, shaped into an arrow point. It attaches with a small piece of monofilament line to a canoe-paddle shaped piece, which is stuck into the second notch.

There is also a little bow that is tied around the top of the paddle and wedged into the bamboo with a small slit cut through a few layers of the tube. This bow acts as a spring.  This particular trap has its bow, paddle and trigger painted blue.

The boys were searching for mounds of earth—small burrows made by land crabs. Once they found a hole of a certain size, they would set the trap as shown above and stick it into the hole like this:

Land crabs would come out of their burrows at night in search of food. They would crawl up the bamboo tube until they hit the small notched pin in the top of the trap (seen in the triangular-shaped slot cut in the trap above.) That would release the bow, which engaged the small paddle. The paddle acted as the door and tripping it caught the crab in the tube.

Land crabs were then either eaten by the hunters or sold. They are delicious!