Dear Jim: I have been searching in some databases of pollination and the info available refers that Trillium is self sterile (it need the activity of pollinator for seed set) and most species are pollinated by bumblebees, flies, ants and beetles. The fly you have observed is probably a Syrphid fly not a Drosophila, i guess. Syrphid flies use to eat pollen and pollinate as well. You can check this publication for more information and references: ___________________________ Tammy L. Sage, Steven R. Griffin, Vincenza Pontieri, Peter Drobac, William W. Cole and Spencer C. H. Barrett 2001. Stigmatic Self-Incompatibility and Mating Patterns in Trillium grandiflorum and Trillium erectum(Melanthiaceae) Annals of Botany 88: 829-841 Post-pollination processes governing mating patterns in Trillium, a well-known genus of insect-pollinated woodland herbs, are poorly understood. Mechanisms influencing outcrossing were investigated in T. grandiflorum and T. erectum, two widespread species native to eastern North America. In southern Ontario, Canada, the two species are often sympatric; they flower in early May, and are pollinated by different assemblages of insects. Controlled cross- and self-pollinations and structural observations of pollen germination and pollen tube growth were conducted to determine whether the two species possess a self-incompatibility (SI) system and, if so, the specific site(s) of self-rejection. Controlled pollinations indicated that both species set significantly more seeds from cross-pollination than self-pollination, implicating the action of SI. This was confirmed by structural studies which demonstrated that self-recognition and rejection reactions occurred on dry-type stigmatic papillae. Observations of pollen hydration revealed that self-rejection was rapid, being initiated within 10 min of pollination and prior to pollen tube emergence. Final self-rejection resulted in failure of pollen tube growth at the base of stigmatic papillae. SI was expressed more weakly in T. erectum and thereby resulted in considerable self-seed set in some individuals . Estimates of outcrossing rates using allozyme markers indicated that T. erectum displayed a mixed-mating system whereas T. grandiflorum was more highly outcrossed. Structural studies of pollen traits indicated that the two species differed with respect to the size of grains and their aggregation with implications for pollen dispersal and mating. The ecological and evolutionary implications of the variable expression of SI in Trillium are discussed. ____________________ In your case if the 2 species of Trillium has diferent pollen shape (color, size, etc), perhaps you can capture the flies using a dry method so pollen is not washed and then extract the pollen from the bodie of the flie and observe it using a microscope, in that way you can see if the flies visit the 2 species or only one of them. Hope this help Best wishes Germán At 11:19 11/05/2008, you wrote: >Hi Kelly, > >I'm just referring to anything that transports pollen from one flower to >another in a manner that results in pollination of the recipient flower, so >I use "vector" in the broadest sense. It had not occurred to me before >that there might be a methodology involved in establishing that a >particular bug was a true natural pollinator of a given plant species. > >Jim Shields > >At 09:06 AM 5/11/2008 -0500, you wrote: > >Hi, Jim. I don't have an answer. I would ask are meaning "pollinator" > >and not "pollination vector", unless you are talking about disease carriers? > > > >Mr. Kelly M. Irvin > >10850 Hodge Ln > >Gravette, AR 72736 > >USA > > > >479-787-9958 > >USDA Cold Hardiness Zone 6a/b > > > >http://www.irvincentral.com/ > > > >_______________________________________________ > >pbs mailing list > >pbs@lists.ibiblio.org > >http://www.pacificbulbsociety.org/list.php > >http://pacificbulbsociety.org/pbswiki/ > >************************************************* >Jim Shields USDA Zone 5 Shields Gardens, Ltd. >P.O. Box 92 WWW: http://www.shieldsgardens.com/ >Westfield, Indiana 46074, USA >Tel. ++1-317-867-3344 or toll-free 1-866-449-3344 in USA > > >_______________________________________________ >pbs mailing list >pbs@lists.ibiblio.org >http://www.pacificbulbsociety.org/list.php >http://pacificbulbsociety.org/pbswiki/