Nepenthes bicalcarata (fanged pitcher plant)
Nepenthes bicalcarata, a distinctively ‘fanged’ pitcher plant from Borneo, has a mutually beneficial relationship with ants living inside its tendrils.
About this species
Nepenthes bicalcarata is a pitcher plant from Borneo with two, distinctive fang-like structures that emerge below the lid of each pitcher. The specific epithet bicalcarata derives from the Latin bi, meaning two, and calcaratus, meaning spurred. In 1880 British explorer Frederick Burbidge described these protrusions as ‘walrus-tooth-like prickles’ and likened them to rat-traps.
Early speculation over the function of the spurs included the suggestion that they may deter insectivorous mammals such as tarsiers from removing insects from inside the pitchers. Now it is thought likely that the nectar that accumulates on their tips attracts insects, which then fall off the spurs into the pitcher fluid below.
In addition to feeding on captured and digested insects, N. bicalcarata also obtain nutrients through a mutually beneficial relationship with a species of ant living inside its tendrils.
Geography & Distribution
Nepenthes bicalcarata is native to Borneo, where it is found in northwest Kalimantan, Sarawak, Brunei and southwestern Sabah.
It is locally common in peat-swamp forest and sometimes also occurs in heath forest on white sandy soils. It has been found at up to 950 m above sea level.
Dried specimen of Nepenthes bicalcarata from Kew’s Herbarium
Overview: A terrestrial climber up to 15 m tall. Stem circular in cross-section, about 2 cm in diameter.
Leaves: Thin and stiff, up to 65 × 14 cm. Petiole (leaf stalk) up to 12 cm long, narrowly winged. Nectaries usually present on lower surface of petiole, next to stem. Ten or more longitudinal nerves on each side of midrib.
Pitchers (modified parts of leaves): Greenish orange, with orange to red flush from the covering of hairs. Peristome (collar around the opening) green, rarely red. Lid yellowish above, marbled deep red or purple below.
Lower pitchers up to 13.0 × 6.5 cm with two fringed wings. Nectaries scattered across surface of pitcher. Peristome up to 2 cm wide, ribbed, inner margin with teeth about 0.6 mm long. The uppermost 10–12 ribs are drawn out into a pair of downward curving, sharply pointed thorns up to 2.5 cm long. Lid kidney-shaped. Tendril swollen, up to 12 mm thick, with a thin-walled spot facing the pitcher surface that is often hollowed out and inhabited by ants.
Upper pitchers up to 13 × 6 cm, with two prominent ribs. Lid up to 4 × 10 cm. Tendril once-coiled.
Male flowers: Tepals deep purple to blackish, 5 × 4 mm, borne in clusters of up to 15 flowers on inflorescences up to 1 m long.
Female flowers: Borne on inflorescences that are shorter than the male inflorescences.
Fruits: Capsules with valves to 3.0 × 0.5 cm. Seeds not yet recorded.
Insects are believed to be attracted to nectar produced by large glands covering the pitchers, especially on the lower surface of the pitcher lid. The ridged and toothed edge (peristome) of the pitcher makes it difficult for any animals that fall in to climb back out. They usually die inside the pitcher, drowning in the liquid secreted in its lower half, where they are then broken down by digestive enzymes into nutrients that become available for use by the plant.
Unusual relationship with ants
Pitchers of Nepenthes bicalcarata often have a swollen tendril with a thin-walled spot that is sometimes hollowed-out and inhabited by ants. These ants (Camponotus schmitzi) benefit not only from a nesting space, but also obtain nutrition from extrafloral nectar and by recovering prey items from pitcher fluid.
Fanged pitcher plant is thought to benefit from this relationship in a number of ways. The ants may fend off herbivores and animals seeking to remove prey items from the pitchers. By removing and consuming large, indigestible prey items they may also protect pitchers from putrefaction. Additionally, research has found that these ants regularly clean the surface of the peristome (collar around the opening of the pitcher). This cleaning increases the prey capture efficiency (by keeping the peristome smooth) and extends the life of the pitcher (it remains functional for longer and hence does not need to be replaced by energy-expensive new growth).
Threats & Conservation
Nepenthes bicalcarata is locally common in peat-swamp forest in parts of Borneo but has been assessed as Vulnerable (VU) according to IUCN Red List criteria.
Nepenthes species are listed on CITES Appendix II, meaning that trade in wild collected plants is subject to controls.
Nepenthes species are cultivated worldwide by carnivorous plant enthusiasts.
Nepenthes bicalcarata is cultivated in the Tropical Nursery (one of the behind-the-scenes areas) at Kew.
The Nepenthes collection is one of the few for which Kew still uses a small amount of peat. A coir-based mix has been tested but was not suitable and hence a perlite and peat mix is used. Kew is committed to reducing its use of peat even further and is trialling a range of alternatives from pure Seramis (expanded clay particles) to finely chipped bark.
Plants are kept at 20–24°C during the winter and vents are opened if the temperature reaches 26°C in the summer. They are misted daily (but only on sunny days during the winter), twice daily during the summer. Plants benefit from the strong light of a south-facing position and small weekly feeds of liquid fertiliser.
This species at Kew
Nepenthes bicalcarata can be seen growing in the Tropical Carnivorous Zone of Kew’s Princess of Wales Conservatory (Zone 8).
This newly redeveloped zone is home to many other species including Nepenthes truncata, N. rafflesiana, N. vietchii and the recently described N. robcantleyi. Growing alongside these are Amorphophallus paeoniifolius and A. variabilis.
Dried and alcohol-preserved specimens of Nepenthes bicalcarata are held in Kew’s Herbarium, where they are available to researchers from around the world, by appointment. Details of some of these specimens, including images, are available online in Kew’s Herbarium Catalogue.
Leaves, pitchers and a stem of Nepenthes bicalcarata collected by British explorer Frederick Burbidge (1847–1905) are held in Kew’s Economic Botany Collection, where they are available to researchers, by appointment.
Kew’s work on Asian pitcher plants
Kew has a long tradition of work on Nepenthes. Joseph Hooker, a former Director of Kew, completed the first revision of this genus and described many of the world's most spectacular species.
Kew's micropropagation unit pioneered development of cultures from seed in the 1970s and 1980s. Species such as Nepenthes rajah, which had been highly threatened by the collection of plants from the wild, became widely available through subsequent tissue culture work carried out by various nurseries.
Keep up to date with events and news from Kew
- newly discovered
- around the world
- of use
- ground breaking
- english garden
- garden plants
- english heritage
Plants & Fungi blogs from Kew
27 Jan 2014
Alan Paton, Assistant Keeper of Kew's Herbarium, describes some of the problems associated with plant names and the importance of the new release of The Plant List.
16 Dec 2013
Rhian Smith takes a closer look at Christmas trees and their relatives, and describes the scientific work Kew is carrying out on the taxonomy, biogeography and evolution of this important group of plants.
09 Dec 2013
Sarah Cody explains how gap analysis is helping our partners collect the seed of crop wild relatives (CWR) for a project called 'Adapting Agriculture to Climate Change', run jointly by Kew's Millennium Seed Bank and the Global Crop Diversity Trust.
25 Jan 2013
He may be a Seed Morphologist but Wolfgang Stuppy of Kew's Millennium Seed Bank discovers there is more to the snake gourd than just some strange fruit and eccentric seeds.
03 Jun 2013
The southeast Asian plant Durian has been called the King of Fruits but, like Marmite, it sharply divides opinion between those who love the incredible taste of its custard-like pulp and those who are revolted by its putrid smell.