Nepenthes Inermis - Carnivory

Carnivory

Nepenthes inermis produces extremely thick mucilaginous pitcher liquid. It is so viscous that if a pitcher is held upside down, the fluid will pour out, forming an unbroken stream several metres in length. This fluid coats the entire inner surfaces of the pitchers in a thin film. The pitchers of N. inermis function not only as pitfall traps but also as flypaper traps, with the sticky inner walls trapping flying insects above the surface of the fluid. The fluid also acts as a lubricant, allowing prey items to easily slide down into the bottom of the pitcher cup.

The upper pitchers of N. inermis are frequently tipped over during downpours. The rainwater that accumulates in them is lost, but the extremely viscous fluid, together with the laterally appressed walls, ensure that the contents is retained. No longer holding heavy rainwater, the pitchers quickly spring back to an upright position. A similar trapping method may be employed by related species such as N. dubia, which also produce very viscous pitcher fluid.

Nepenthes inermis pitchers mostly trap flying insects, particularly those of the two fly suborders: Nematocera and Brachycera. However, they do not normally contain invertebrate pitcher infauna.

It has been suggested that glands on the lid secrete compounds that intoxicate visiting insects, such that they lose their footing and fall into the pitcher.