As the Badab War ground on and the number of casualties mounted, the Mantis Warriors were forced recruit an ever growing number of initiates to compensate for the Chapter's Battle companies inability to keep a full contingent of Tactical Squads. In an effort to ensure that the Chapter could still call upon full strength Battle companies to defend the Mantis Warriors home world, the chapter's Reserve and Scout Companies were dissolved and their numbers were added to the remaining Battle Companies. In doing so, several Scout Squads were permanently added to Captain Mantodea's second company, a shift from the Codex Astartes that has continued long after the the Mantis Warriors reunification with the Imperium.
Scout Squad Ultis was formed late in the Siege of Tranquility. Although their sniper rifles were poor use against the Carcharodon Terminator legions, they mainly attacked from the rear of the advance, taking out servitors, chapter surfs, and other non-combat personnel in an effort to slow down the Space Shark warmachine and ultimately make any time spent on Tranquility as miserable as possible for the invaders.
That was a bit of a long winded fluff piece but I hope you enjoyed it. To be honest I don't recall why I decided to paint up these scouts. I've played a few games with them and they are terrible. BS3 with sniper rifles is rubbish, not to mention the squad costs the same as 10 Eldar Rangers. Well they are painted now so I'm sure they will make their way into some future lists.