Utricularia caerulea is a bladderwort widely distributed across Asia and Australia. In Australia, it occurs in warmer parts of 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 sometimes 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 usually a shade of purple or white in colour, with a touch of yellow at the palate. The inflorescence is often crowded, with many flower heads bunched together at the end.
The bladderwort is widely distributed across warmer parts of Australia and across SE Asia. In Australia, it is not picky about its habitat, growing in waterlogged terrestrial niches such as seepages, creek beds, springs and seasonally moist heathlands.
U. caerulea is similar in morphology to several other species like U. geoffrayi and U. nivea. It is distinguished from U. geoffrayi by its entire lower corolla lip (those of U. geoffrayi are usually divided into three shallow lobes) and lack of yellow eye dots at the palate (the palate of U. geoffrayi features two yellow dots on top of bulbous protrusions). It is distinguished from U. nivea by its larger size and (sometimes) crowded inflorescence and purple colouration (The blooms of U. nivea are invariably white, small and occur singly or are well spread along the inflorescence).