Aquatic insect life histories partition resources temporally as species whose life cycles reach completion are replaced by newly hatched species. Biological monitoring programs that use benthic macroinvertebrates as a means of evaluating water quality often sample only once or twice during a year. Thus, evaluations that are made based on the basis of only a few samples may be inaccurate if important community shifts are not realized. A series of metrics is used collectively to measure particular attributes of a community when making assessments. A suite of metrics was calculated and evaluated using the coefficient of variation (CV) for samples that were collected at 10 evenly spaced dates during one year at a reference stream in central Missouri. The CVs indicated that some metrics are more stable than are others over the annual period and are probably better candidates for biomonitoring. Closer examination of individual metrics revealed that particular taxa are responsible for the resultant variability. Degree days are suggested as a means of calibrating highly variable metrics.