There are only two grappler (attacker and defender) and a lot of supporter. The supporter perfom the assist action to grant the grapplers a +2 bonus to CMD or CMB. The first attacker maintains the grapple with +18 (for 9 assisting formians) on his CMB and then he performs the attack action for 1d6+4 damage. Thats all ..
Multiple Creatures: Multiple creatures can attempt to grapple one target. The creature that first initiates the grapple is the only one that makes a check, with a +2 bonus for each creature that assists in the grapple (using the Aid Another action). Multiple creatures can also assist another creature in breaking free from a grapple, with each creature that assists (using the Aid Another action) granting a +2 bonus on the grappled creature's combat maneuver check.
Aiding in a grapple is exactly the same as Aiding Another to attack. No damage bonus, just a +2 to cmb.
In melee combat, you can help a friend attack or defend by distracting or interfering with an opponent. If you're in position to make a melee attack on an opponent that is engaging a friend in melee combat, you can attempt to aid your friend as a standard action. You make an attack roll against AC 10. If you succeed, your friend gains either a +2 bonus on his next attack roll against that opponent or a +2 bonus to AC against that opponent's next attack (your choice), as long as that attack comes before the beginning of your next turn. Multiple characters can aid the same friend, and similar bonuses stack.
You can also use this standard action to help a friend in other ways, such as when he is affected by a spell, or to assist another character's skill check.