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Studies on the Mating Flights of the Ephemeroptera I. The Mating Flights of Ephoron album (Say) and Stenonema canadense (Walker)

1958; Florida Entomological Society; Volume: 41; Issue: 1 Linguagem: Inglês

10.2307/3492627

1938-5102

Thomas B. Thew,

Fish Ecology and Management Studies

During the evenings of July 23 and 24, 1956, the author was fortunate in being able to observe the mating flights of Ephoron album (Say) and Stenonema canadense (Walker). They occurred at the same locality-a highly commercial area of the waterfront along the Mississippi River in Rock Island, Illinois. The exact area was a rocky bank approximately 100 feet in length. In both instances the sun had just begun to set. On July 23 the sky had scattered clouds, but the air was warm and still; while on July 24, large thunderheads were beginning to appear and a gentle breeze had commenced to blow. The time of the first observation on July 23 was 7:20 p.m.; on July 24 it was 7:15 p.m. The first flight to be observed on both evenings was that of Ephoron album; the males were seen to fly from the water to the rocky bank, where they shed their subimagal pellicle. On July 24th some time was spent observing this phenomenon. The mayflies would fly from the water and alight on the rocks or anything available (including people). A firm grasp on the substrate was necessary before the process could begin. In some cases a specimen was seen alighting in several places before it found a substrate which suited it. Then followed a period of from ten to fifteen seconds in which the specimen gently shook its wings, evidently to separate the imagal wings from the subimagal pellicle. After this, the thorax was slowly arched and the wings folded against the body, thereby commencing the release of the forewings and forelegs. The long forelegs appeared to be greatly compressed within the short subimagal ones. Soon the mesoand metathoracic legs were free and the insect began to crawl forward. The subimagal skin was not cast off the head, the pronotum, and mesoscutum, although it was shed from the remaining parts of the body. The posterior portion of the abdomen was freed at the same time as the posterior portion of the wings. A few seconds were then taken to release the genitalia. The time period from the first arching of the thorax to the freeing of the genitalia varied from forty to fifty seconds. The mayfly then flew off with the cast pellicle of the abdomen and wings, which had remained in one piece, still attached to the caudal filaments and trailing behind like a white banner. The time element from first alighting to the resumption of flight was almost invariably one minute.