As they move in the team realizes that any effort to fly will give them away instantly. While the bigs have only had a chance to clear out a small radius around the hive, the height of the things is such that their sentries would see anhy approachers from miles off if flying above the treeline. This means walker the armor in the old fashioned way.
But a mission like this comes with its complications. You need more intelligence on the motion and activity of the enemy around the hive. You need to know when they are in and when they are out. As well as how many other bugs are flying about that could return and reinforce the battle if it should take place.
Bugs like this use all kinds of nasty tactics. After all, while most people forget Gridia will never forget these are intelligent monstrosities, capable of human level reason and tactics.