PREY CAPTURE BY DIONAEA MUSCIPULA A REVIEW OF SCIENTIFIC LITERATURE WITH SUPPLEMENTARY ORIGINAL RESEARCH.

Many descriptions of prey capture by Dionaea muscipula (Venus flytrap) in popular publications and educational literature are inaccurate. Here we review well documented literature on prey capture in this plant's natural habitat and add observations on prey capture and attraction mechanisms we have observed in plants cultivated in a greenhouse and garden. Despite its common name "Venus flytrap" does not specialize in capturing flies. About 70% of the prey it captures in its native habitat consists of spiders, ants, and beetles. Flies are only oneto-eighteen percent of what it captures. In a greenhouse where flies, capable of entering the vents, composed most of the available prey, over 90% of the prey captured were flies. Dionaea cultivated in a garden captured a diverse array of animals, only about 37% of which were flies. Dionaea is a generalist, capturing a wide variety of prey species. Its capture mechanism does not appear to have a "syndrome" analogous to the Pollination Syndrome in flowers where a specific floral type is pollinated by a specific animal (i.e. Bee Flowers or Fly Flowers). The measured capture rates of Dionaea are low, about one capture/leaf/month in its native habitat. Similar but lower rates were measured in the greenhouse and garden. The single measurements in each habitat need to be repeated, but the low rates are consistent with the observation that wherever it is observed Dionaea has nearly all of its traps open. Both the low capture rates and the large number of open traps suggests that alluring agents drawing prey either do not exist or are ineffective. Despite reports of nectar secretion by Dionaea traps, our observations show that unstimulated traps are always dry unless wet by rain, condensation, or a sprinkler system. Secretion occurs only after prey capture. Alluring glands along the outer trap margin have been reported to be visited by small ants that work their mouthparts over the glands. We have photographed a fly exhibiting the same behavior. The exact nature of this behavior needs to be further investigated, but it does not appear that this attractant can act at a distance since flies are as likely to land on the outside of a trap as on the inside. Darwin proposed that the trap closure mechanism allows small prey to escape, preventing the expenditure of energy on captures likely to be of little benefit. Recent measurements of prey captures indicate that traps show little selectivity based on prey size and that while traps could, in theory, select larger prey, statistically they do not behave this way. [ABSTRACT FROM AUTHOR]