For those of you who have trouble understanding how gnats could kill a chicken, I have posted the following picture. This is the result of a single buffalo gnat bite. Now chickens don't swell like this, but you can imagine the effect of the toxins that must be present in multiple bites that chickens are susceptible to. In addition they can suffer from blood loss, and plain out suffocation from hundreds of gnats blockin their respiratory passages. The scab on the nose is a coop injury, not attributable to gnats, I dropped a lift-up door on it.