Can Escallion be replaced by onion? Green onions are said to be milder than onions, which would suggest that if one do not mind the more powerful onion flavour in a particular dish then onions could be used in place of green onions.

My assumption could be wrong here; I am not a chef but a poor father trying to cook. I want to substitute green onion for Escallion in some Caribbean recipes, and several internet sites say that Escallion is green onion - but, confusingly, some Caribbean cooking websites are saying that Escallion is not green onion.

Could someone clear this up for me? Is Escallion the same as scallions (green onions)?  And can Escallion be replaced by onion in a recipe?
A little research seems to suggest that escallion is not scallion :

Escallion - The escallion (Allium ascalonicum L.) is a culinary herb. Grown in Jamaica, it is similar in appearance to the British spring onion, American green onion, Welsh onion and leek, though said by Jamaicans to be more flavourful. Like these others, it is a (relatively) mild onion that does not form a large bulb.
(from Jamaica Cooking Dictionary )

Now ... 'Allium ascalonicum' is not what most countries consider 'scallions' (that'd be the 'Allium fistulosum'); ascalonicum is what we normally call 'shallots' ... so it's possible that they have a variety of shallot (aka 'multipier onion') that's bred for the green tops.
A little further digging suggests that the Allium ascalonicum L. is specifically 'wild onion', which I know I have growing in my lawn (but only really harvestable in the spring, before I start mowing for the season).  It's possible that there are regional variations, but I'd say that wild onion tops are closer to chives, but that might also come from my harvesting them before they've fully matured.
...
All that being said, I substitute things all the time.  I'd probably cut down the amount of onion (or use a milder red or yellow sweet onion), go with chives or shallots, or as @belisarius mentioned, go with leeks.
update: and in walking through my yard today, I noticed that the wild onions are back up above the grass, so at this time of year, you might have a free (and closer) substitute -- if your yard has areas where it looks like densely packed chives, and if you cut some, it'll have an onion-y smell, then you most likely have wild onions.