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Pitfall traps

Cunning pitfall-traps are perfectly evolved to defeat their light-footed insect prey.

Pitfall traps 

Cunning pitfall-traps are perfectly evolved to defeat their light-footed insect prey. 

The trap’s lip is glassy-smooth, and a microscopic stairway slopes downward. Stumbling inside, the prey’s feet become clogged by tiny wax crystals that break off the walls ... and they fall. 

Sequence of a pitcher plant pitfall trap in action

1. Putting on a Show - The plant signals insects with colours that mimic a flower’s ultraviolet landing-pattern. Near the trap’s mouth, sweet nectar lures prey closer to the edge...

2. Slippery Slope - The smooth lip of the trap is super-slippery when wet, and impossible to grip. The victim’s feet slide on the slick surface, and they tumble into the abyss.

3. Certain Doom - The trap walls are waxy or covered in downward pointing hairs. The victim falls into digestive fluid and drowns, then slowly dissolves.

Plants with bite – lobster pots

Putting on a show - lower pitcher of Nepenthes rowanae with preying mantis, Cape York Greg Bourke

Slippery slope – (common name?) Nepenthes trusmadiensis, Borneo Greg Bourke

Certain doom - Pitcher plant (Nepenthes lowii x zakriana) with prey. © G Bourke

Frog on pitcher plant (Sarracenia flava) Greg Bourke

Pitfall traps of Pitcher plants growing in The Calyx, Royal Botanic Gardens, Sydney Image - Caroline Seltz

Pitfall traps activities

  • Observe the structural adaptations of the plant. Draw and label a scientific diagram of its pitfall trap. Label its features and outline the function of each.
  • ​Construct a 3D model of the plant, replicating the plant’s structural adaptations such as colours and surfaces. Use a model of an invertebrate to demonstrate the plant’s trapping mechanisms.
  • ​Pitfall traps are used by scientists to catch and study crawling ground-dwelling invertebrates. Use the structural features of the pitcher plant’s trap to construct a pitfall trap to collect invertebrates. Insert it into a garden bed at ground level and leave it overnight. Next day, extract the trapped invertebrates. Use magnifiers to examine their features and infer their structural adaptations.
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