Bikōchū

The Bikochu beetle is an insect that was once used by the Aburame clan in the Great Ninja Wars. It was becoming an endangered species, however, so they let it live in a special bug habitat, uninhabited by humans. Two of the female's distinguishing traits are its long nose and its blue eyes, but a giant bug-like creature that looks exactly like it is sometimes confused with the real thing. It also has an incredible sense of smell; stronger than even a dog's. The species only lays eggs every several years, in a certain breeding season. The female only lays eggs on a day succeeding a rainstorm. Soon after one hatches, it goes into the pupa stage. After this, it is not long before it metamorphoses into an adult. The thing about the Bikochu that inspires bug-users to go after it is the fact that the first scent that the beetle detects after its metamorphosis stays in its memory, so whenever it smells it again it tries to get to the source of the scent. This is what makes Bikochu beetles coveted, since it can be used as a formidable tracking device.

In the filler arcs, Tsunade sent Naruto Uzumaki, Shino Aburame, Kiba Inuzuka, and Hinata Hyuga pursue it in the hopes of locating Sasuke Uchiha, but simultaneously the Kamizuru clan was pursuing it also, to restore their clan to its former glory. The Leaf ninja managed to retrieve an egg, but Naruto flatulated right after it metamorphosed. Sakura Haruno didn't take the news of that lightly and the Bikochu Beetle managed to help her find out where he's hiding during her chase upon him.