For the moth, I went back and forth between just outside Voljin's to down and just to the right of Teldor. I killed one in each place (yes, I'm THAT guy) and ran to the othert to look and it was there. Stopped to check Royal Moths and Waterflys for secondaries and found none.
For the firefly, found near and to the immediate right of Southport, near and to west south west of Axefall, and at the north tip and south tip (after the curve) of the road going thru the town with the Arak pet daily in it.
I think I have been within site of a town or settlement just about every time I have seen one and haven't seen one out in the boonies at this point. Therefore I would say stay near the town and if you don't see it run to the next area. Have your minimap all the way out and tracking pets on. Use a mod that tells you in the minimap tooltip if you have it or not (I think I use collectanator).