EMERGENCE PHENOLOGIES AND PATTERNS OF AQUATIC INSECTS INHABITING A PRAIRIE POND

Abstract

Emergence traps were used to investigate aquatic insect emergence patterns and densities in a prairie pond in Saskatchewan. Hill's numbers, percent dissimilarity and Morisita's Index were used to measure the diversity of each insect order and changes that occurred between 1987 and 1988. Emergence between submerged vegetation habitats and emergent vegetation habitats were compared. One hundred and fifteen species belonging to six orders were identified: three Ephemeroptera, 16 Odonata, one Neuroptera, 17 Trichoptera, eight Hymenoptera, and 70 Diptera. One new species was identified. Another was a new record for the genus in Canada. Twelve species are new records for Saskatchewan. The emergence patterns of the abundant species ranged from unimodal for the Odonata, including Lestes congener, to multimodal for many of the chironomids: eg. Corynoneura cf scutellata. Some species, including Psectrocladius simulans, had long emergence periods of over three months while others, such as Cladopelma viridulus, had short emergence periods of two weeks. Diversity and abundance of the insect community declined between 1987 and 1988. These decreases were attributed to the pond changing from a permanent, nonaestival pond in 1986, to a permanent, aestival pond in 1987, and to a temporary pond in 1988. These changes in physical conditions of the pond reduced the numbers of adults collected for most species in 1988 because the immatures did not survive the aestival conditions. Diversity and abundance were reduced further in 1988 because the pond dried up in mid July, restricting the species collected to those emerging in spring and early summer. significant differences in the number of adults collected from the submerged vegetation and emergent vegetation were recorded for some species including Callibaetis pallidus, Aeshna interrupta, and Mesosmittia acutistylus? These were due to differences in microhabitats of immature stages, eclosion requirements and water depth at the trap stations. The insect communities of 1986 and 1987, particularly Chaoborus americanus, Callibaetis pallidus, and the Zygoptera species, were used to predict the physical conditions of the pond a year prior to the study. Knowledge of life histories and habitat requirements of the species were used to predict the insect community in 1989 based on the conditions of the pond in 1988.