Sweep sampling capture rates for rangeland grasshoppers (Orthoptera: Acrididae) vary during morning hours

摘要

Rangeland grasshoppers have long been considered pests of serious economic importance and are key components of grassland food webs. Sampling protocols inform decisions to control grasshoppers. Preliminary observations while sampling rangeland grasshoppers indicated differences in species diversity and numbers captured, depending upon time of day. To test these differences, we used USDA-APHIS sweep-net sampling protocols at various times at four rangeland sites during 2006-2007 and compared mean numbers collected. Sweep sampling every hour from 06: 00 to 12:00 revealed that adult and nymphal grasshopper numbers were significantly higher at 06:00 than either 07:00 or 08:00. Captures were similar throughout the afternoon. These patterns were also observed for adults of the most common species, Melanoplus femurrubrum (DeGeer). The results of this study have important implications for rangeland pest management decisions and ecological studies that estimate insect biomass as an indicator of food availability. Our results indicate that standardized sampling of grasshoppers in mixed-grass prairie rangeland should be conducted between 10:00 and 16:00.