Bladderworts have active traps. These plants are aquatic, terrestrial and frequently amphibious growing on pond margins. Aquatic varieties are often found as mats of plants floating in quiet, acidic ponds and bogs. The terrestrial forms are found growing in damp, sandy, acid soils. Bladderworts are often overlooked and only noticed when they are in flower. The flowers are often yellow, but can range from white, coral, and violet. They emerge above the water, often in large numbers, and can be a very colorful highlight to the bog waters. These rootless plants form branching feathery whorls. The bulbous traps are generally quite small, less than an 1/8 inch (3 mm) and are attached to the fine branches. The trap contains a small opening with a hinged lid surrounded by many branched plant hairs. While at rest, fluid inside the trap is slowly absorbed, resulting in decreased water pressure inside the trap. When a small prey brushes against one of the sensitive trigger hairs, an electrical action potential opens the trap door and the prey is "sucked" into the trap. Digestion takes several days. Bladderworts can ingest a large number of mosquito larva and are ecologically valuable.