When Naraku first met Sesshomaru he gave him the Poison Insects' hive. He said to use it Sesshomaru must throw it and then they will come out of the hive. When Sesshomaru did, Miroku tried to pull them in with his "Wind Tunnel", but the insects' venom harmed his right hand by poisoning it.
In this other episode the Poison Insects disguise themselves as Kikyo's Soul Servants because it will make InuYasha and the others think Kikyo is in that direction. It appeared to be a trap inside the people's worst fears using Naraku's Illusory Death. InuYasha's was the day he was pinned to the tree, Shippo's being left behind with only the main casts' clothes, Miroku being sucked in his Wind Tunnel, Sango being killed by Kohaku, and Kagome getting her jewel shards stolen.( And where InuYasha was in love with Kikyo.)
Submitted by Roan Quiozon