And of every living thing of all flesh, two of every sort shall you bring into the ark, to keep them alive with you; they shall be male and female.
All Commentaries on Genesis 6:19 Go To Genesis 6
Augustine of Hippo
A further question asked by the curious concerns those tiny creatures, smaller even than mice and lizards, such as locusts, beetles, flies and even fleas. Were there not more of these in the ark than the number prescribed by God? Those who raise this difficulty must first be reminded that the words “that creep on the earth” imply that there was no need to preserve in the ark animals that live either in the water like fishes or on the water, as certain birds do. Second, the words “male and female” imply that there was no need to have in the ark such animals as are not born in the normal way but populate from putrid or inanimate matter. Or if they were in the ark, they could have been there as they are in our houses and not in any definite number. On the other hand, if the sacred mystery that was there being enacted demanded down to the last number of nonmarine animals the perfect accord of symbolic figure and historical fact, then God took care of this in his own way and did not leave it to Noah or his family.