Aquatic habitats with immature populations of the Culicoides variipennis (Coquillett) complex were sampled across the United States and tested for soil chemistry parameters. Indicators of organic loading, phosphate, percentage of organic matter, and nitrate were high for C. variipennis and C. sonorensis, reflecting the common occurrence of larvae in sediments contaminated with livestock waste; these factors were low in western playa lake habitats with immature C. occidentalis. Levels of salt-forming ions and indicators of salinity, notably sodium, chloride, magnesium, sulfate, boron, and conductivity, were elevated in substrates supporting all 3 species, with values that declined from very high to high across the arid west to moderate east of the Mississippi river, and differed significantly among species. Concentrations of boron differed most strongly among habitats of the respective species, ranging from exceptionally high values in playa lake substrates with C. occidentalis, to high and moderate levels in western and southeastern sites with C. sonorensis, to moderate levels for substrates in the east with C. variipennis. The presence of C. sonorensis in dairy wastewater lagoons and saline springs in geographic regions that are otherwise inhabited by C. variipennis may reflect salinity factors that regulate the distribution of the C. variipennis complex.

Culicoides variipennis adults were reared from media with nine concentrations of rubidium (Rb) ranging from 0.0 to 1,000 ppm. Rubidium levels were measured using an atomic absorption spectrophotometer. Concentrations of 500 and 1,000 ppm of Rb reduced pupal production, adult emergence, and adult longevity; lower levels of Rb had no noticeable effects. Adult females reared from media containing 15.6 ppm Rb were marked for a period of at least 13 d, and Rb levels were unaffected by a blood meal on day 3. One marked fly was readily detected in a pool of five. This technique should be useful in studying the dispersal behavior of C. variipennis under field conditions.

Selenium (Se) content of elk, mule deer, bison and beef skeletal muscle was measured and compared. Selenium content was determined by graphite furnace after wet nitric acid digestion. Game samples did not differ in Se content but contained more Se than beef (wet weight) (PcO.05). On dry weight basis, deer contained more Se than elk, bison or beef (PcO.05). Within samples from male elk and deer, and elk and bison of both genders, there were interactions between species and muscles (PcO.05). Type of muscle and gender did not influence Se content (P