Kikaichū

are a species of small, beetle-like insects that seem to be exclusively native to Konohagakure. These special 'ninja insects' are bred and utilized exclusively by the Aburame clan for their unique techniques. In combat, the Kikaichū are also recognized as a kind of Ninja Tool, similar to the use of Ninken by the Inuzuka clan, or other ninja.

In the series, it is shown that all members of the Aburame bug-user clan actually live in symbiosis with the kikaichū through a Hiden Jutsu, called the Destruction Bug Host Technique: The Aburame clan, shortly after birth, allows the kikaichū to live and breed inside the their bodies, and in return through this practice, the host ninja receives the life-long ability to control and command the bugs, using them as their primary fighting technique. Additionally, due to having simpler nervous systems, the kikaichū are less likely to be affected by Genjutsu--which are designed to affect the more complex nervous systems of humans.

The kikaichū can fly, and they will typically move in swarms when on the attack, or in smaller numbers when practicing stealth. A female bug can be left on a target and then they can be tracked by smell, or scout bugs can be sent out and return to tell the host information about the area. Thanks to the kikachū, Aburame clan members are experts in communication and espionage, due to their ability to communicate with the insects, stealth because the kikaichū make no noise or motion during combat, as well as in search-and-seizure missions.

The most common use of the kikachū in combat is to ambush an opponent and drain them of their chakra before they notice the bugs at work. This process can leave the victim with so little chakra that it leaves then unable to fight and thus killed or taken in for questioning. Other uses include simply tracking down a target, serving as a a protective shield and as a prison to hold and detain a target in place.

Usually, since the kikaichū only have a lifespan of a few hours, they are always breeding safe within their host, maintaining their numbers. Because of their short lifespans, the kikaichū are easily expandable in combat, it is easily decided to send them out and not expect them all to come back. If large numbers of the kikaichū should be wiped out, then the bug-user can utilize the Secret Technique: Insect Cocoon technique, a technique which can be used to rapidly breed a whole new generation of the kikachū, repopulating their numbers.

Since the kikachū only have a lifespan of a few hours, their life cycle ensures that there will always be females with eggs. Any variations that prove useful to the individual bug, and consequently the bug-user, in combat such as immunities will be passed on to the next generation, which can then be cultivated for their success against dangerous opponents in combat. The immunities gained from the kikachū can be used as a defense mechanism; by exerting chakra, the original source of the immunities can be rendered useless or can be destroyed on contact. For example, when the kikachū gained immunities to Guren's unique Crystal Release, they were able to resist being crystallized, and were able to shatter her techniques on contact.

Trivia

 * Kikai, when written as 奇怪, means "strange", or "mysterious".