The plant Aristolochia microstoma uses a unique trick: its flowers emit a fetid-musty scent that seems to mimic the smell of decomposing insects. Flies from the genus Megaselia (family Phoridae) likely get attracted to this smell while searching for insect corpses to mate over and lay their eggs in. When they enter a flower, they are imprisoned and first pollinate the female organs, before being covered with pollen by the male organs. The flower then releases them unharmed.
Source: T. Rupp, B. Oelschlägel, K. Rabitsch et al.
Rupp and colleagues sampled A. microstoma plants from three sites in Greece: one West of Athens and two on the Peloponnese. From 1457 flowers (of which 72% were in the first, female phase) they collected a total of 248 arthropods, ranging from flies from four families to centipedes and springtails. "The study shows that the flowers of A. microstoma emit an unusual mix of volatiles that includes alkylpyrazines, which are otherwise rarely produced by flowering plants. Our results suggest that this is the first known case of a flower that tricks pollinators by smelling like dead and rotting insects rather than vertebrate carrion," says corresponding author Prof Stefan Dötterl, the head of plant ecology group and the Botanical Gardens at the Paris-Lodron University of Salzburg, Austria.
When pollinators enter an Aristolochia flower, they are guided by hairs downwards to a small chamber which holds the sexual organs. Trapped inside, they deposit any pollen they carry onto the female organs, before the stamens ripen and release more pollen. When the hairs that block the entrance to the chamber wither, the pollinators can escape, and a new cycle can begin.