Noah Whiteman presents "A New Look at an Old Nemesis: Are Desert Mistletoes Generators of Biodiversity in the Sonoran Desert?" from 6 to 7:30 p.m., Tuesday, Oct. 22; free. The lectures are held in the library of the old Desert Laboratory, the first structure on the right among the buildings that are roughly halfway up the hill. Reservations are requested; email to [email protected], or 629-9455.