Perhaps it is the sunlight on the water that lures semaphore flies into the small aquarium at the end of the garden, the arena in which they perform their entertaining courtship ritual.
Poecilobothrus nobilitatus is small but exquisite, 7 mm long, with emerald green eyes that burn in the sun with an internal crimson fire, a bronze colored body that is streaked with green and purple iridescence, and in males white spots on the wing tips. It can walk comfortably on water, long legs, supported by surface tension, where its feet leave tiny dimples.
Their performance might have gone unnoticed, but the aquarium is at eye level so our grandchildren can watch the unfolding water dramas through its transparent sides.
The male semaphore fly’s courtship dance follows a predictable pattern. He spots a female eating on the surface of the water, and a brief dogfight ensues, which is fought with such speed and agility that it is impossible for the naked eye to follow. She settles back down on the water and he lands in front of her, white wingtips whirling in a desperate attempt to announce his intentions, which is often met with utter indifference. Usually she continues to feed and rarely turns to face him. I have observed these rituals over the swimming duckweed many times and have not yet seen a successful mating.
Throughout the afternoon, schools of water fleas perform their own jerky dance right under the flies’ feet, sometimes falling prey to female semaphore flies which fish for them through the meniscus. Silver, sunlit oxygen bubbles from pondweed surge to the surface. Diving beetles race into the depths while their limbs paddle frantically to counter the buoyancy of the scuba tank air bubble trapped under their wing cases. Water saddles, the pond’s garbage recycler, tumble through the mud on the bottom. Pond life in summer revealed by the simple magic of glass.
And everything is suddenly haunted by chaos, in the form of the blackbird bathing in the tank on hot afternoons. Spray flies in all directions, but when it’s gone before the waves subside, the never-giving semaphore flies have returned to their wobbly dance floor.
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