Meteorological factors influencing host-seeking activity of female Simulium luggeri (Diptera: Simuliidae).

The influence of selected meteorological variables on host-seeking activity of parous and nulliparous female Simulium luggeri at cattle bait was studied in central Saskatchewan. Variability in the pattern of diurnal host-seeking probably was attributable to the secondary influence of meteorological parameters on endogenous rhythms that are primarily stimulated by illumination. Although some differences occurred, nulliparous and parous female S. luggeri activity was similarly influenced by the meteorological factors measured. The most important limiting factors were wind speeds greater than 15 km/h, followed by temperatures less than 20 degrees C. When values were outside of these thresholds, saturation deficit, cloud cover, barometric pressure, and illumination became influential. Parous S. luggeri appeared to be more tolerant of dry conditions than nulliparous individuals. Seasonal differences, site location (exposed versus protected), and varied interactions among environmental factors contributed to the inconsistent relationships among meteorological variables and black fly host-seeking activity.

Residues of methoxychlor and other chlorinated hydrocarbons in water, sand, and selected fauna following injections of methoxychlor black fly larvicide into the Saskatchewan River, 1972.

In May 1972, 0.309 ppm methoxychlor black fly larvicide was applied in a single test on the North Saskatchewan River. Eight to nine days later residues of 0.05-0.10 ppm methoxychlor occurred in sand 21-22 km downstream from the point of injection. Methoxychlor was not detected in water, insect larvae, shellfish, or muscle tissues of three fish species on the same sampling date. Perhaps because of relatively high oil content in goldeye fish, methoxychlor residues in muscle tissues were 1.0-1.5 ppm in 8 percent of those sampled, 0.21-0.99 in 21 percent, and 0.02-0.20 in 37 percent. In 34 percent of the goldeye fish no residues were detected. Goldeye and other fish collected before or 17 weeks after this injection did not contain detectable levels of methoxychlor. River water in two samples of the injected slug of water collected 6.5 km downstream from the point of injection contained 0.14 and 0.16 ppm methoxychlor. The suspended solids filtered from these sample contained 40 and 47 percent of this methoxychlor (437 and 892 ppm, respectively). Thus methoxychlor may act selectively against filter-feeding species, especially black fly larvae.