Utricularia caerulea is a bladderwort widely distributed across Asia and Australia. In Australia, it occurs in Western Australia, Northern Territory, Queensland and Northern NSW. The species is named for its colouration, which confusingly is purple, rather than caerulean.
The species has a domed lower corolla lip which features white striped markings akin to the jaw of a cartoon skull. The spur is wide at the base, tapering to a point and pushed forward beneath the lower corolla lip. The uppper corolla lip is unremarkable. The flower is purple in colour, with a touch of yellow at the palate. The inflorescence is often crowded, with many flower heads bunched together at the end.
I observed the species growing in sandy substrates at the edge of small creeks in the Northern Territory.
U. caerulea is similar in morphology to several other species like U. geoffrayi and U. nivea but can be recognised through its usually crowded inflorescence of purple flowers at the terminus of a thick peduncle.