During my hikes in the North Woods a couple weeks ago, I wondered how trillium were pollinated, speculating that the role was probably filled by solitary bees rather than wind. I've subsequently found this:
Trillium grandiflorum has been studied extensively by ecologists due to a number of unique features it possesses. It is a representative example of a plant whose seeds are spread through myrmecochory, or ant-mediated dispersal, which is effective in increasing the plant's ability to outcross, but ineffective in bringing the plant very far...That discussion relates more to seed dispersal than to pollination per se, but I thought it was interesting (and totally new to me).
Fruits are released in the summer, containing about 16 seeds on average. These seeds are most typically dispersed by ants, which is called myrmecochory, but yellow jackets (Vespula vulgaris) and harvestmen (order Opiliones) have both been observed dispersing the seeds at lower frequencies. Insect dispersal is aided by the presence of a conspicuous elaiosome, an oil-rich body attached to the seed, which is high in both lipids and oleic acid. The oleic acid induces corpse-carrying behavior in ants, causing them to bring the seeds to their nesting sites as if they were food. As ants visit several colonies of the plant, they bring genetically variable seeds back to a single location, which after germination results in a new population with relatively high genetic diversity...
Although myrmecochory is by far the most common dispersal method, white-tailed deer have also been shown to disperse the seeds on rare occasions by ingestion and defecation. While ants only move seeds up to about 10 meters, deer have been observed to transport the seeds over 1 kilometer... Thus occasional long distance dispersal events, such as by deer, probably helped save this and other species with otherwise short distance dispersal ability from extinction during the glaciations of the ice ages.
Bent Trillium photographed by me at Honey Creek State Natural Area (Wisconsin), May 2008.