The Saimyōshō (Hell Wasps) are Naraku's insects, his demonic wasps. They are used for retrieving Jewel shards, spying on various people, or to prevent Miroku from using his Wind Tunnel, as their poison is deadly. On the weak side for demons, many of them are killed by Inuyasha and his friends: their only strength is in their numbers. Saimyōshō resemble bees and, like bees, they lose their stingers and die when they sting others. They often accompany Naraku or his incarnations, but will obey Naraku's orders over those of one of his incarnations. They are seldom dangerous by themselves. In swarms, one unique ability they seem to possess is that they are capable of merging their bodies together to forge demon body parts: one instance is when they regenerated into an arm for Musō during his fight with Inuyasha, another in Jaken Falls Ill, they bonded together to form a severed ogre arm to attack Rin in the forest, also during that time they also seem to be able to dissemble their merge form by whim.
When Inuyasha storms Naraku's Castle with the Red Tessaiga, Kagura is ordered to stop him from proceeding. She starts to fight Inuyasha, but goes easy on him, as she wants him to succeed in killing Naraku. When she sees the Saimyōshō watching her, she thinks to herself that they know she is losing on purpose, suggesting that the insects are quite intelligent. It would also appear that Kanna has some connection to the wasps, as she can use them to show images in her mirror, like video cameras. It is unknown whether she is simply able to use them, or if she is, in fact, their master, as it is not told exactly when Kanna was created and where the wasps come from. They live in nests or hives like regular wasps and bees, and are most often seen in forested areas, suggesting that they are herbivores, and try to avoid contact with humans.
In the Band of Seven arc, Naraku uses the Saimyōshō (and occasionally Kohaku) to relay orders to the undead mercenaries, like when they order the band of seven to flee battle because they would lose, or when they tell Bankotsu that Renkotsu betrayed and killed Jakotsu.