For ME beetle patterns are one of MY dry "go to" patterns for searching the
water, fishing to fish I've seen when nothing specific seems to be hatching,
and for fishing to risers when they won't accept my "hatch matching"
efforts. Larry's Fishing Rule #19 " After some refusals to your best
entomological marvel ties, rest him and show him a beetle before you give
up." g

I'd probably pick a #14 or 16 black foam beetle, tied with a peacock
underbody, rubberlegs, and a dab of bright poly on the back to help me see
it, in that oft contemplated "you can only have one dry fly" situation

YMMV

PS another benefit? you can tie them VERY fast and they last a long time
if you run tying thread through the peacock to strengthen it

PPS do NOT be afraid to try some HUGE beetles for searching ... I bet
you'll be pleasantly surprised