Sampling Methods for E122

Since sweep-net samples give excellent estimates of relative abundance within orders, and good estimates of relative abundance between orders, the main method of sampling the insects in the prairies and savannas was sweep-net. Insects were also collected using pitfalls in some of the prairies and savannas. Once during the growing season ants were sampled using scent plates.

Sweep-net sampling occurred within each field using 100 sweeps per sample.

Pitfall traps were placed at the end of 4 permanently marked transects within the sites sampled. Five scent plates were placed evenly from end to end along the transects, thus providing 20 samples per site. The transects were parallel to each other, 25m apart, and in the prairies 40m long and in the savannas 50m long.

Insects were sampled 7 to 9 times throughout the 1992 growing season. All specimens were manually sorted and identified to species (89.8% of specimens) or morphospecies within known genera or families. 

Species biovolume, an index of biomass, was calculated as the average product of length (from tip of head to top of abdomen), width (maximum width of body or head) and thickness (maximum thickness of body or head) for 5 specimens in the oldest life stage for each Orthoptera species. Even though body size increases greatly during development, this method seemed justified since most species (84%) only occurred as adults in the samples taken.  To minimize counting a species twice, all larvae were examined by outside experts and, if they might have been the same species as an adult insect, they were counted as a single species.

Voucher specimens were deposited in the Cedar Creek insect collection.



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