Nectar Robbery and Thievery in the Hawk Moth (Lepidoptera: Sphingidae)-Pollinated Western Prairie Fringed OrchidPlatanthera praeclara

Abstract

ABSTRACT Nectar larcenists target flowers with a long nectar spur. The western prairie fringed orchid, Platanthera praeclara Sheviak and Bowles (Orchidaceae), has a 50-mm-long spur and is pollinated by hawk moth (Lepidoptera: Sphingidae) species with tongues that are shorter than the spur.We placed net traps above inflorescences at P. praeclara sites in southeastern North Dakota to survey potential nectar larcenists, including hawk moth thieves (2004–2014) and bumble bee robbers (2007–2014).We captured two hawk moths, Manduca quinquemaculata (Haworth) and Agrius cingulata (F.), that have tongues over twice the length of P. praeclara's spur. Also captured were eight bumble bee species (genus Bombus), which may produce the holes discovered in P. praecala's spur. Holes triggered loss of the spur and its nectar. In 2007, 2013, and 2014, robbery was observed in 10, 60, and 37% flowers per plant, respectively. At the flower level, robbery had a positive effect on removal of pollinaria and no effect on pollen de...