unidentified millipedes

Description:

Dark brown millipedes ~ 25mm long with lighter colored legs.

Habitat:

Suburban neighborhood on an insular tropical upland plateau.

Notes:

Spotted on a painted wall along a sidewalk. In total six were spotted at once along ~ 2 m of wall; usually none is observed. I don't know anything about the life cycle of these creatures, but perhaps six were present because several individuals matured at the same time from a clutch of eggs laid in the area.