It is out of character for red to give creatures toughness bonuses without power bonuses. Also, the second ability on your suggestion doesn't involve the enchanted creature at all -- it might as well be a global enchantment, in that case. Also, black has had a handful of ants in the past. It shared Army Ants with red and had Carrion Ants all to itself. It also has its share of insects, even though some/most of them are not ants, per se.
If I were to make this red, I think it would be something like a better firebreathing:
Cloak of Ants

{R}
Enchant Creature
Enchanted creature gets +2/+0.

: Enchanted creature gets +1/-1 until end of turn.
If I were to make this green, it might be something like this:
Cloak of Ants

{G}
Enchant Creature
Enchanted creature gets +2/+0.
Sacrifice Cloak of Ants: Regenerate enchanted creature
(the gren variant is a much better [card]Carapace[/card])