After hitting my "brick wall" with Euclide and his father several years ago, I gave up researching for a while. When Ancestry emailed the free 1940's records search a few days ago I have managed to get a few more snippets of information. This in turn led me to familysearch.org - BUT I hadn't searched for him as a Beffre (I've now viewed the image.)
Euclide's and his brother appear as Beffre in 1925 but in the 1930 census Elias is back to being a Theriac and continued to use that name until he died...so I assume it was an error made by the family and census taker at the time.
After 1925 Euclide seems to disappear which is why I think he may have gone to Canada.
Again, thanks for your input.