The back-and-forth movement of the hindwings directs a predator's attention to the less vital part of the hairstreak's body. It is better to have a chunk missing from the pretty wings than to give up the head.

Red-banded Hairstreak (Calycopis cecrops) on a warm (82 F) and pleasantly breezy November day at the U.S. National Arboretum.

Nine other butterfly species observed including two White-M Hairstreaks, four Azures, Ocola Skippers, Fiery Skippers, Sachems and one Checkered Skipper.

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Some studies of butterfly behavior suggest that male butterflies determine their potential mate by sight looking for a specific wing pattern and color. When a male sees a female he releases special chemicals known as pheromones (contained in his wings) while vigorously fluttering his wings. The male may perform a courtship dance flying close behind or above the female to get her attention. Each species has a unique courtship dance. If the female is interested she may join the suitor in the dance. If successful, they fly away to a secluded location to mate.

I have not been able to find information about the speed of their fluttering wings. Post your answer if you know, please.

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Driving over the Penobscot Narrows River Bridge in Maine.

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