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Good question! The m-dot pages might not actually be indexed at all. Check out this article, and specifically the section I'm quoting: https://searchengineland.com/google-advice-switch-m-dot-domain-responsive-mobile-first-index-rollout-277446 "The rationale is that right now, Google has a desktop-first index. So Google doesn’t really index your m-dot; they just annotate the m-dot URLs, but there is no true indexing of your m-dot content..." You might first want to double-check that Google is actually indexing the mobile site as you suspect, or simply marking up search results with the subdomain. Mobile-first has been a slow rollout, which might not have hit you yet! This might help you check if you have indeed been moved: https://blog.seoprofiler.com/google-check-log-files-find-site-moved-mobile-first-index/ If they are indexing, then yes -  you'll have to make sure the URLs migrate appropriately to the new responsive site, and keep a close eye on mobile traffic changes in Search Console. Hope this helps a bit! Mike

Thanks Kate,  the  https://s3.amazonaws.com/images.seroundtable.com/hreflang-google-mobile-first-1511959807.png is really what I needed. Cheers!