Will,
I'm not confused, far from it and generally try my hardest not to confuse anyone else.
The fact that different species of Ephemerids are found in different habitats and simply will not be present in some places is a damn good reason not to use the accepted common name for one particular Ephemerid to describe any insect from that order.
I'd certainly never use 'Mayfly' generically when teaching as it has an accepted meaning, it refers to something specific. To do so could be confusing and is factually incorrect and I'm not in the habit of wilfully teaching stuff that is incorrect or confusing, whether it sounds good or not. If you consider that to be picky then fair enough, I can live with that 
Enough debate about Claret Duns, I need to finish my Mayfly box (like proper actual Mayflies for anyone who may be confused) for my upcoming trip.
Ben
Cheers
Ben
OK. Fair enough Ben. Your logic is unassailable, I accept that.
Nevertheless, it seemed that most of the people reading this thread are either (a) happy to use the terms interchangeably and or (b) can cope with the fact that a single term can mean two things without their brains exploding or the sky falling in.
The problem Ben, is that "Mayfly" isn't a scientific term (that's why we have Danica etc) it's a common name, and it is FACTUALLY CORRECT to say that "Mayfly" has TWO accepted meanings. Just because you don't accept one of them doesn't make it go away.
On the teaching thing I say words to the following effect:
"This group of insects are referred to as either up-wings or the mayflies. The latter term can be confusing because there is a single species which, in the UK, is known as The Mayfly. etc. etc."
This gives them all the info they need. It prepares them for the fact that many people and books refer to the group as mayflies, as well as telling them that it may refer to a single species.
What
will confuse them is ignoring the fact that the term "mayflies" can have two meanings. Tell them it has two potential meanings and they know to ask clarifying questions to get the facts straight.
W.
