Bug? I'm getting 3-4 Chrysallids popping up out of the ground half a map away and MOVING ACROSS the entire map to hit my guys.

So I'm on an Retaliation mission and turn 1 I aggro 2 'lids. No big deal I think, until on the very next turn about 4 of them pop out of the ground OUT OF LINE OF SIGHT then proceed to move about 30 squares into my squad and melee them. Surely this is a bug?