i'm not an entomologist, but it looks like one to me.
i have it in a ziploc bag in the freezer.
a few things.
1) i have no physical signs of bites, and no reason to think the bugs have been downstairs for a long period.
2) i have no proposed source.
3) so, they would have to have migrated from upstairs to downstairs - and i think the totality of evidence makes that obvious.
there's a non-trivial possibility that it's some other kind of bug. again: i'm no entomologist. but, it does certainly look like one to me.
i have no requests for action in the basement. again: i have not been bit. but, if you required evidence for action upstairs then i may have it for you.
(pause)
the only other thing i can think of is that it might be booklice.
fwiw, i found it walking on the hallway floor - nowhere near the bed.
anyways - i don't have bites. i can't complain if i don't have bites! but if you need evidence for upstairs, i may have some.
or, if the problem from upstairs has become more obvious over the last little while, it may be spreading.
(pause)
on second thought, i saw a second bug this morning and i think it's not a bed bug but a roach nymph. i'll hang on to the body for a few days.
that would be more consistent with what i've noticed down here.
i've checked my body carefully - still no signs of bites.
j