Key: Name (Level range according to Wowhead, Subzone: Zone) *Notes*
4.1 Silithid Ant Tameables:

Copper
Gorishi Worker (51-52, The Slithering Scar: Un'goro Crater)
Hive'Zora Hive Sister (55-60, Hive'Zora: Silithus) *Did not see any 57+ mobs*
Hive'Zora Waywatcher (55-59, Hive'Zora: Silithus) *Did not see any 57+ mobs*

Tan
Zukk'ash Worker (38-45, The Writhing Deep: Feralas) *Did not see any 40+ mobs*
Vekniss Drone (60, Temple of Ahn'Qiraj)
Vekniss Hatchling (60, Temple of Ahn'Qiraj)

Pink
Centipaar Worker (47-49, The Noxious Lair: Tanaris)
Hive'Regal Slavemaker (55-60, Hive'Regal: Silithus) *Did not see any 57+ mobs*
Zukk'ash Tunneler (38-46, The Writhing Deep: Feralas) *Did not see any 40+ mobs*
Hive'Zara Collector (60, Ruins of Ahn'Qiraj)

Blue-green
Hazzali Worker (46-48, The Gaping Chasm: Tanaris)
Hive'Ashi Defender (55-59, Hive'Ashi: Silithus) * Did not see 57+ mobs*
Vekniss Soldier (61, Temple of Ahn'Qiraj)
Hive'Zara Hatchling (60, Ruins of Ahn'Qiraj)
Hive'Zara Drone (60, Ruins of Ahn'Qiraj)
Notes:
* For each mob, I tamed them, checked to be sure they had the correct talent trees, and dismissed/recalled a few times to be sure they are stable colors.
* There are no color changers.
* They are all now the correct size when tamed (previously one model was tiny after taming).
* They still show quite low in the Character Pane (pet pane).
* I believe that the Wowhead level listing is also listing pre-Cataclysm levels, so I've included both level ranges here.
* There are two mobs NOT listed, because both require a quest to summon:
- Silithid Swarmer
- Arakis <Hive'Zora Overlord>
* There is also one Silithid Ant which is not tameable: the level 1 Nerub'ar Scarab, a neutral Borean Tundra mob classed as Undead.
* Some of the Ruins (20-man) and Temple (40-man) Ahn'Qiraj mobs are Elite.