As everyone knows, cockroaches are supposedly the only creatures able to survive a nuclear explosion.1 Well, I think I've found the pre-atomic, chemical equivalent! It's from a novel published in 1926:
Poison gas in the open is one thing. Dropped on a densely populated town like London it's quite another. Suppose you dropped enough to make a lethal atmosphere all over London to a depth of forty feet, not a single living thing could survive, not one -- except flies. Curiously enough, they are immune.
Source: the Earl of Halsbury, 1944 (London: Thornton Butterworth, 1926), 25.2
This is a new one on me, I wonder if this idea became as popular as the cockroach version later did?
It also has grave implications for the future of life on this planet, because chemical weapons are easier to develop than nuclear ones and so that will give the flies an advantage over the cockroaches in the eternal struggle for supremacy ...