Found: SciFi short story mystery of psychic alien with remote appendages

Read as part of an anthology in 1980s
The protagonist must discover an immobile alien is psychic and controls what appears to be unintelligent small creatures as its sensors and tools. The alien "brains" live in caves (or similar) never venturing out, but their remote creatures are quite common and generally ignored by the human settlers.

Bump. Still hoping someone will have a suggestion about this one.

The description above was mostly accurate. I was remembering "The Handicapped" by Larry Niven, in Neutron Star.