Photo 7/24/04, Cook County, MN
These are carnivorous plants, inhabiting fens, bogs and peatlands in the northern latitudes. Pretty as they may be, these peatlands are killing fields. Insects are attracted to a sweet mucilage secreted by the glandular hairs on the sundew leaf. The hairs are thigmonastic, that is, they move in response to touch or vibration. The hairs converge on the struggling insect. The musilage contains enzymes: chitinase, esterase, peroxidase, phosphatase, protease. The mucilage secretion is stimulated by specific molecules. A quote from Matusikova 2005: "The reaction of sundew leaves depends on the molecular nature of the inducer applied." And from Gallie 1997, regarding pitcher plant (Sarracenia purpurea), another carnivorous plant found in fens and bogs: "Hydrolase expression is induced upon perception of the appropriate chemical signal."
This is to say, the glistening tentacles of sundew respond to touch and the chemistry of the insect that lands on them, inducing the plant to produce enzymes and to curl the tentacles around the insect.
The purpose of all of this is to convert the insect into digestible material for the plant, enabling it to live in a nutrient-poor habitat, such as bogs are.
Yes, like a cold fog, death creeps across the sodden moor.
That is not all. These northern bogs have two other carnivorous plants. Pitcher plant traps insects in a leafy vase filled with rainwater and enzymes. The vase is lined with sharp spikes, like concertina wire, preventing any escape. Bladderwort (Utricularia) has a submerged bladder under negative pressure that has a trap door and a lever. A water flea or mosquito larvae that touch the lever open the trap door, sucking it into the bladder within tenths of a second. Once again, it is bathed in digestive enzymes.
The insect dies within 15 minutes, and it is safe to say that these are the most horrifying 15 minutes of his brief, hapless life, as the powerful enzymes attack his defenseless, softening body and reduce it to a soupy meal.
We are pleased that insects do not scream, at least in a range heard by humans.