Function of the heater: the dead horse arum revisited.

The dead horse arum, Helicodiceros muscivorus, is a conspicuous, foul smelling and thermogenic plant of the Araceae family. This Mediterranean arum lily copies several aspects of a carcass in order to attract carrion blowflies, which are subsequently exploited as unrewarded pollinators. We have previously shown that this plant exhibits a highly accurate olfactory carrion mimicry, which serves to attract the blowflies. In this study, we have investigated the role of thermogeny in the arum. We show that the thermogeny has a direct effect on the pollinators, altering their behaviour. By manipulating heat and odour release of the plant, we can show that the heat, produced along the appendix, is important to lure the flies to this structure, which is vital as the flies from the appendix are more prone to enter the trap chamber that houses the female and male florets. This study provides rare evidence for a direct functional role of thermogeny.