The third plague that God sent to Egypt during the time prior to the IsraElite exodus was a countrywide infestation of small, biting insects. The Greek word for them is skniphes, which has been translated as gnats, fleas, mosquitoes, etc. We have decided that they were likely some sort of flea, because gnats aren’t thought of as biting insects, and the text indicates that they lived on the ground, which would rule out mosquitoes.