Like a lot of things, the takeover of “the blob” wasn’t noticeable at first. Sure, you’d see the blob here and there, but you didn’t think much of it. At the time, you didn’t even know it had a name.

Blackworms (Lumbriculus variegatus) are distant relatives of rainworms, measuring up to 10 cm long. They live in shallow marshes, ponds, and swamps in Europe and North America, where they feed on ...