Fish Behaviour - Mating Or Establishing Shoal Hierarchy?

This should probably be in a section entitled "fish behaviour" which I'm quite fascinated with.

I've already mentioned the recent episodes of hyperactive behaviour at http://www.thinkfish.co.uk/forums/index.php/topic,2141.0.html , similar to what happens when fish are first introduced to the tank.

The 6 x-ray tetras have been behaving like this for the past 3hrs - chasing one another round and round the tank, and up and down the entire length and width of the rear glass, while the 6 harlequins are behaving naturally amidst all this hyperactivity. On close inspection, it seems to be the following:
* One female rests at one particular point in the tank, while individual males swim up to her and she chases them to the other side of the tank before resuming her original position.
* The other, largest female seems to be chased by the 3 of the 4 males, so that she takes the lead with the other 3 almost conjoined to her, up and down the length and width of the glass, round the heater, and in among the plant leaves - enough to induce a form of dizziness/seasickness in anyone watching.
* The two smallest males seem to be involved in frequent duels/tussles although sometimes a harlequin ends up in their path and gets pushed out of the way.

I have never actually seen any sign of eggs in the females - in fact, I'm only assuming the two females are indeed females because they are largest - but one in particular (and possibly both) seems to be particularly greedy and skilled at acquiring food as well as scouring the sand for leftovers.  I have never seen any eggs being released or in the tank. 

My questions are:
* Is this mating or just re-establishing the hierarchy in the shoal?
* With having had the x-ray tetras for 13mths and the harlequins for 6mths, ought I to have seen eggs before now in either/both species? [NB. I spend a lot of time at home, and sit in front of the fish, whether at leisure or working when they are in my line of sight beyond the laptop.]
* Presumably, even if there have been no eggs laid in this time, this isn't any actually cause for concern?

I would say a bit of both. My Penguins do a similar thing.
The larger female would sit in open water, as it were, whilst the males would come up and get chased off, which I'm sure she's picking out a suitable mate.
For hierarchy sorting, every now and then, two of them would chase each other around the tank. Nothing else really happens other than a bit of butting and the rare fin nip.
As for eggs, I asked about different species adopting young, bit it was more likely my male krib was guarding a tasty feeding area littered in tetra eggs. So I would suggest any eggs would be quickly eaten unless you've provided some form of carpet for the eggs to fall and be safely hidden. Seriously Fish goes into the breeding habits in a lot more detail.