MonoMonday....Distant.....

......entertainments.....this fine selection is from May 1919, found this morning when I was doing a bit of local history research into bathing machines on Tynemouth Longsands (don't even ask!) on the British Newspaper Archive......but y'know, I can never resist reading the small ads ;-) 
But, here's the question, what ARE Mexican Insurrection Dancers anyway, were they 'mainstream variety' or more of a 'niche market' act?.......I did a google search but I'm no wiser (and I'm probably now on a priority CIA watch list!)
Answers, preferably in code, by pigeon post please ;-)