How were the Giant Hornets actually defeated? In Shinsekai Yori (From the New World), the Robber Fly colony uses the Akki (Fiend) to disarm the Giant Hornet soldiers. 

However, in the 18th episode of the anime, it is also revealed that the Giant Hornet soldiers were reduced to nothing but lumps of flesh. 

How is that possible? I understand that the Akki is immune to the death feedback when considering humans, but the Akki couldn't have possibly done that to the Giant Hornets, the Akki could have at most disarmed the soldiers. 

That being said, how did the Giant Hornets die? Or is this something that is lost in translation? (I was watching the Japanese version with English subtitles).
I don't think it was ever stated how exactly they were wiped out, but we do know that it wasn't a WMD (no damage to the surrounding land), it wasn't the fiend that killed them (death feedback), and that the fiend stopped their arrows and disarmed them. It's also possible the fiend prevented the Giant Hornet soldiers from attacking any of the Robber Fly and that's why none of them were killed. Being unable to fight back, all the Robber Fly soldiers had to do was slaughter them all.

That could also be the reason Kiroumaru was the sole survivor of the battle, in order to bring suspicion onto him from the humans. The Robber Fly could have purposely let him live.