Longchaeus insularum is a species of sea snail, a marine gastropod mollusk in the family Pyramidellidae, the pyrams and their allies.

[1] The shell has a yellowish color, banded and spotted with chestnut, with fine longitudinal white raised striations, appearing like low rounded riblets, with occasional darker macillations, especially on the base.

The suture and periphery are channeled.

The columella is straight, three plaited.

[2] This species occurs in the Pacific Ocean off Hawaii.