* Shape and size: Both are long, cylindrical, and segmented. Blackworms tend to be smaller and thinner than earthworms, but still have a similar overall body structure.

* Color: As the name suggests, blackworms are black or dark brown, similar to the color of some earthworms.

* Movement: Both blackworms and earthworms move using their muscles and bristles. They "inch" along, leaving a trail behind them.

However, there are also some key differences:

* Habitat: Blackworms live in aquatic environments, while earthworms live in soil.

* Breathing: Blackworms breathe through their skin, while earthworms breathe through their skin and specialized structures called "saddles."

So, while blackworms may not be earthworms themselves, they do share a number of physical and behavioral similarities that make them seem like miniature versions of their terrestrial counterparts.