One thing in general about the people living in North Wales is that they are generally short in height compared to people who live in South and Mid Wales. True that Corris is on the boarder between Mid and North, but it is generally noticable. Is like the natives are built to H0 and if one heads south one enters 00 territory. (Those who understand model railways will understand what I mean).
It is one of the ways one can tell in North Wales who is native and who amongst the tourists or an incomer to the area.
The main reason is that in the South, they grow potatoes as their soil and their climate is most suitable for these crops, so people living in those parts ha e more potatoes in their diet, and we all know that to grow tall one puts manure in ones wellies, but few of us have the time to do that for the duration of our youth though some solitary people (Due to smell) try. Well, potatoes grown in manure has the same effect without the smell, so people living in South Wales grow tall, while in North Wales people try to grow such crops but when they dig them up, all they get are rocks which if eaten gives them weight but does not provide growth. But in North Wales they do have to look out for stone worm which can, if untreated knaw through hones and even gristle. Is why the native "Rissoles" are rarely found in North Wales as to catch those rounded creatures one has to go in the habbitat they thrive, and stoneworm in North Wales tends to eat them alive to the point where they have become extinct. Not many places have a habitat that are favourable to these shy little creatures, and South Wales is one of the rare places in the world where they can survive and thrive, with areas in Pembrokeshire famous for their potatoes also house whole communities of those little creatures who can survive as they don't have issues with stoneworm as stoneworm are not found in those parts.
[There is another reason in the South West of Wales is that their unique enviroment partly sheltered from Ireland, is gently drenched with the purest of rain throughout the year with interludes of sunshine shining through allowing for the rare and unique climatical atmosphere where sunflakes fall, while up north, snowflakes abound instead. South Wales does get snow when the temperature drops below freezing, hut rarely anywhere else does one see the delicate little misty sunflakes fall which has refreshed many a cyclist on their way home! It is their unique and gentle climate is why Pembrokeshire potatoes are one of the few potatoes that do not need peeling, as if one wants to boil potatoes in a pan, the potato growers provide rounded potato-like stones in with the sacks of potatoes so one can place them in the saucepan along with the potatoes, so the gentle moving of the semi-floating potatoes in the water in the pan will gently peel the potatoes on the rounded stones, so perfectly peeled ready potatoes come out of the pan when cooked. Many outsiders who do not know this just chuck the stones and are completely unaware why farmers include these hard to find stones in the sacks. Other types of potatoes have the occasional stones picked by accident, but Pembrokeshire potatoes are unique in this, as carefully selected stones are included in the sacks all as part of the service completely free of charge!]
{Also worth note, is that Pembrokeshire does have areas of slate with a lovely distinctive light blue shade. The shade comes from being drenched by centuries of sunflakes falling from the sky. If one travels into the depths of South West Wales, one may see these slated roofs which are distinct in colour and are different from the many roofs which were slated by the various darker shades of North Wales slate which by nature of much of North Wales being built on rocky slate, had a more plentiful supply!}
There are slate areas in the north of Wales which have no stoneworm but who can plant potatoes in such places, which is another reason why rissoles don't survive. Rissoles which survive by eating the potato worm tend to live in areas where pototo growing thrives, which is why in South Wales from Newport in the east to Fishguard in the west one will find shops selling rissole and chips along with fish and other tasty delights!