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- Title
Timing of Hexagenia (Ephemeridae: Ephemeroptera) mayfly swarms.
- Authors
Corkum, Lynda D.; Ciborowski, Jan J.H.; Dolan, David M.
- Abstract
Although degree-days can be used to determine when insect emergence begins, peak swarming events in species that exhibit extended emergence periods are difficult to estimate. With the aid of logistic regression, we estimated the probability of adult mayfly swarms (≥50 individuals/m2), occurring on any given night in western Lake Erie, using meteorological data. We sampled adult Hexagenia Walsh, 1863 from 2130 (sunset) to 2300 on 18 dates in 2000 (2 June – 18 July), with the largest numbers retrieved between 13 June and 2 July. Water temperature (20 °C) was the cue to the onset of swarming (subimagos). Highest mean (±SE) density of all Hexagenia adults (subimagos and imagos) was 24 740 ± 8 757 individuals/m2. Overall, 10-fold more imagos (mostly females) than subimagos were attracted to lights. Of the factors examined (air and water temperature, Julian day, dew point, heat index, humidity, moon phase, wind chill, wind direction, wind speed), onshore wind speed (0–9.2 km/h) on calendar dates for which the water temperature exceeded 20 °C was the most significant factor to account for total adult swarms. Eighty-three percent of the 18 swarming events observed in 2000 were correctly predicted. Validity of the model was confirmed with data collected in 2002, during which 5 of 6 swarming events were correctly predicted from the logistic model. Wind promotes adult aggregation at the land–water interface, the effect of which facilitates mating success and predator swamping.
- Subjects
MAYFLIES; HEXAGENIA; EPHEMERIDAE; ANIMAL species; HEAT index; WIND speed; DEW point
- Publication
Canadian Journal of Zoology, 2006, Vol 84, Issue 11, p1616
- ISSN
0008-4301
- Publication type
Article
- DOI
10.1139/z06-169