Skutterchuck
Unknown Enemy 6 is a small bipedal insectoid creature featured in Pikmin 3. They have a similar habbit of picking up objects like Dweevils. However, this creature particularily picks up small round crystaline pebbles to defend themselves. If the player uses a Rock Pikmin to break the pebble, it will scurry away
Its head appears to be concave, allowing it to hold the pebbles. If Pikmin continue to attack it after there are no more pebbles for it to pick up, it will thrust itself upward to launch the attacking Pikmin high into the air, causing them to lose their flowers. When it dies, it flips over and curls its legs in the same stereotypical fashion most insects die.
It doesn't appear to be able to kill Pikmin on its own, but it is assumed that the pebbles it launches could crush Pikmin or the Captains. A single Rock Pikmin thrown onto it while it is unprotected is enough to kill it instantly.[1]
This enemy was seen in the Pikmin 3 Demo at E3, and its true name has yet to be revealed.
Video featuring the bug in action:
Skip to 0:40 to see the bug.