The white-bellied piculet is long and weighs . Adult males of the
nominate subspecies P. s. spilogaster have a black cap with a red patch on the forehead and white spots on the rest of it. Their face is mostly dark brown with white tips on some feathers. Their upperparts are olive brown with diffuse pale grayish barring. Their flight feathers are brown with light buff edges, especially on the
secondaries and
tertials. Their tail is dark brown; the innermost pair of feathers have mostly white inner webs and the outer two pairs have mostly white outer webs. Their chin, throat, and sides of the neck feathers are whitish with blackish bars. Their upper breast is pale yellowish buff with broad black bars and the lower breast and belly are creamy white with wide black spots. Adult females are identical but for no red on the forehead. Juveniles are more heavily barred than adults and have buffier underparts. Subspecies
P. s. orinocensis has mostly plain underparts, sometimes with
vermiculation on the flanks.
P. s. pallidus is essentially the same as the nominate but slightly smaller with a shorter tail. ==Distribution and habitat==