I find that mosquitos from different regions affect me quite differently. So for example NZ and AUS mosquitos barely register while German ones itch quit a lot.

Fully agreed on the sandflies. They actually relate to the topic at hand. Sandflies don't stop sucking unless shooed away. A couple of years ago we were talking to an older couple who lived in fjordland. They had moved away when their first kid was born, because the baby could not chase the sandflies away, so was tormented by sandflies which would sit on it and suck until exploded.