This is in the Summa:
Aristotle says that a female is an occasioned male. But it would be wrong for something occasioned and [hence] deficient to be part of the initial creation. Therefore woman should not have been a part of that world.”  Summa Theologica, 1, qu. 92, art 1, ob. 1
Thomas: “….. the active power of the semen always seeks to produce a thing completely like itself, something male. So if a female is produced, this must be because the semen is weak or because the material [provided by the female parent] is unsuitable, or because of the action of some external factor such as the winds from the south which make the atmosphere humid. … the female is not accidentally caused but is intended by Nature for the work of generation. Now the intentions of Nature come from God, who is its author. This is why, when he created Nature, he made not only the male but also the female” Summa Theologica, 1, qu. 92, art 1, ad 1.