Gigantic ants are used as beasts of burden throughout Faerie. Ants are the only large feral creatures without sapient elvish analogues. The use of feral vertebrates such as horses or oxen would be viewed as bizarre, if not morally repugnant.
Ant-breeding is a profession with a long and honourable history in the South Country, with some families having engaged in the business for generations.
Of note is the fact that there are differing breeds of ants; some small, domesticated house ants are seen in "Personal Diplomacy," and the truculent Elfhamian ant, with its shaggy hairs, played a significant role in the history of Irenaeus the Conqueror...in a way he (the White Elf) had not foreseen.
Flying cockroaches are used as steeds by some evil-doers in "In Hoc Signo Vinces."