They look like aphids... you can blast them off with a jet of water and/or use a solution of horticultural oil/ mild soapy water/ neem oil. You want to get those under control quickly.

Thanks hobbyartisan, that's reassuring. Before you messaged, I took the lemon tree into the shower and brushed off every aphid I could find with a toothbrush and thoroughly rinsed the tree. I'll be keeping an eye on it moving forward.

Boy do those look familiar. lol I have a spray bottle of a 2% Castile soap solution and spray directly on the critters.

Brandon, how many trees do you have? Have you always liked growing citrus? From what part of the world or should I say Zone are you in?

I would take them outside and do that if it's above 35 degrees...

MIke