COS 9-10 - Flower foraging behavior in the nectar feeding moth Hemaris (Lepidoptera: Sphingidae), a mimic of Bombus (Hymenoptera: Apidae)

Monday, August 8, 2011: 4:40 PM
9C, Austin Convention Center
Elena S. Tartaglia, Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, NJ and Steven N. Handel, Graduate Program in Ecology & Evolution, and Department of Ecology, Evolution, & Natural Resources, Rutgers University, New Brunswick, NJ

While the majority of nectar feeding moths in the family Sphingidae are nocturnal, four North American species are diurnal.  Of these, three species – Hemaris thysbe, H. diffinis, and H. gracilis – occur in the Eastern United States, and are commonly known as hummingbird moths or clearwing moths. These Hemaris species mimic Bombus species in appearance, size, and by foraging for nectar. Like Bombus, but unlike other members of the Sphingidae family, they are also diurnal in habit. It is well known that bees such as Bombus forage primarily within rather than between patches and that pollinators such as hummingbirds, butterflies and large moths spend more time moving between patches and travel longer distances in search of pollen or nectar. This has immediate consequences for gene flow dynamics by pollen. However, there is no previous research investigating the foraging behavior of Hemaris in the Northeastern United States, so we asked the question, do Hemaris forage like their Lepidopteran relatives or like the Hymenoptera that they mimic?

From 14-26 August, 2010, I observed a patch of approximately 25 Cirsium discolor flowers. When a pollinator entered the patch, I noted whether the pollinator was Hemaris sp., Bombus sp., or Papilio glaucus. That individual was observed for the duration of its visit to the patch. We counted the number of probes into each C. discolor inflorescence. If the next flower visited was within the patch, the number of probes taken in the inflorescence was recorded. Observations continued until the pollinator exited the patch. This procedure was repeated each time a Hemaris, Bombus, or P. glaucus entered the patch. Observations totaled 100 foraging bouts/field day.


Though they mimic Bombus in morphology, Hemaris do not forage in the same manner as Bombus in this system, nor do they forage like Papilio glaucus. ANOVAs indicate that Hemaris visit significantly fewer flowers per foraging bout than either Bombus or P. glaucus, and probe flowers significantly fewer times than either of the other pollinator types. However, a comparison with other Sphingidae foraging shows that Hemaris also do not forage like their nocturnal relatives. Hemaris moths move from flower to flower quickly, taking few probes in each C. discolor inflorescence and visiting few inflorescences within the patch.  Implications of this work for plant reproduction are that Hemaris may facilitate less inbreeding and more outcrossing for plants, and disperse pollen farther than Bombus or P. glaucus.

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