These look like the nymphs (juveniles) of the Florida Predatory Stink Bug. Despite its name, they occur up here in Maryland as well as a native insect, and they feed on other insects, including those we consider pests in the garden. They are fine to leave alone to provide this benefit and do not need treatment or removal. They may overwinter as adults, which can mean they begin to seek-out warm, sheltered spots as nights get chilly, the same way other types of stink bug routinely do in our area in autumn. Occasionally this means they wind-up in houses but the same approach can be used for them as with Brown Marmorated Stink Bugs, the more commonly-seen species in home landscapes.

Miri