they are aphids. If you don't want to buy an insecticide for just a couple of plants, you can first try just wiping down the plants - both tops and bottoms of the leaves - with a wet paper towel. This will remove/kill most if not all the aphids, and also most of the black spots. You may have to rub the spots a little bit to get them off.
Or spray the whole plant with a fine mist of water from a spray bottle, let it soak for a few minutes and then wipe it off with paper towels.
If they come right back, you might want to try spraying the whole plant - again be sure to get the undersides of the leaves and the stems - with soapy water. Just 1/2 tsp. of dish soap for a quart spray bottle is plenty. Don't think that if some is good, more is better because soap can be harsh if it's too concentrated. Do this at least twice within a week, to get any new bugs whose eggs that hatch after the first treatment.
After that, to prevent a re-infestation, take your plants to the shower at least once a month and give them a good "rain bath". They will thank you for it. Most indoor plants are more or less tropical in nature, so they like the extra humidity.