When it rains, it feeds: The pitcher plant that uses the power of water droplets to catapult ants to their death
By Eddie Wrenn
Almost trapped: Ants can cling to the south-east Asian plant when it is dry, but they will be flung off to their death when it rains
A pitcher plant captures ants ready for digestion - using the power of raindrops.
Pitcher plants have large, slippy rims, which catch unsuspecting insects unaware.
The insects lose their footholes and fall into the pool of fluid, drowning and waiting for digestion.
But this pitcher - nepenthes gracilis- has a novel approach to get ants into the trap.
The bizarre feeding technique used by the pitcher was identified for the first time by scientists from Cambridge University.
A highly-attractive nectar is used to attracts insects to the underside of its leaves. When a raindrop hits the leaf it catapults the bug into another cup-shaped leaf below, which is full of a digestive fluid.
The leaf of the plant is covered in a specialised crystal wax which creates a surface that is sticky enough to allow the bug to walk on it in calm conditions but slippery enough to allow them to drop off when hit by raindrops.
Dr Ulrike Bauer from the University of Cambridge’s Department of Plant Sciences, who led the study said: 'It all started with the observation of a beetle seeking shelter under a Nepenthes gracilis lid during a tropical rainstorm.
'Instead of finding a safe - and dry - place to rest, the beetle ended up in the pitcher fluid, captured by the plant.
'We had observed ants crawling under the lid without difficulty many times before.
'So we assumed that the rain played a role, maybe causing the lid to vibrate and "catapulting" the beetle into the trap, similar to the springboard at a swimming pool.'
To test their theory scientists simulated ‘rain’ with a hospital drip and recorded its effect on a captive colony of ants that was foraging on the nectar under the plant’s lid.
They counted the number of ants that fell from the lid in relation to the total number of visitors to the plant, which usually grows in nutrient-poor areas like roadsides.
They found that ants were safe before and directly after the ‘rain’, but when the drip was switched on about 40 per cent of the ants got trapped by the killer plant.
The bizarre feeding technique used by the Nepenthes gracilis pitcher was identified for the first time by scientists from Cambridge University
The amazing feeding techniques of the plant, which is native to the Malay Archipelago, were discovered by Dr Bauer while she conducted field research in Borneo last June.
The plant has been well known to science for hundreds of years but this was the first time the unique mechanism was documented by scientists.
Dr Bauer added: 'It is amazing to see things like this in the field. The pitcher plants have very unique mechanisms and but this is perhaps the most amazing.
'Scientists have tried to unravel the mysteries of these plants since the days of Charles Darwin.
'The fact that we keep discovering new trapping mechanisms in the 21st century makes me curious what other surprises these amazing plants might still have in store.'
While these plants treat ants as food - sometimes the plants have a more co-operative approach.
A species of pitcher plant in Borneo actually relies on ants to help it ingest larger plants such as flies.
When nepenthes bicalcarata swallows a fly which is too big, or even bigger prey, it relies on an army of ants to come in and clear away the debris.
The ants live at the foot of the plant, with precious nectar to feed their larvae, and they will also chew and then excrete the remains of larger insects.
The co-operation between fauna and flora is even more incredible as, without the ants there, t