Species ID by geography

Hi folks

I’m fairly new here but having fun I must say.

My thought for the day: In many cases, a single species in a given genus is most commonly collected in a particular locality. For example, with water penny beetles in Vermont (and all of the Northeast) we have: Psephenus herricki. There is a different genus, Ectopria, very distinct from Psephenus, also has one species E nervosa. likely to be collected.

What standard do we apply? In the case of the beetles, IDing a larva from a photo works with confidence to genus level but not beyond. Can we use geography to narrow it farther? ANd if so, how certain do we need to be?

Welcome to the forums @declanmccabe, and good question!

I think there is already a discussion thread going for this topic, where you might want to chime in: