Temperature and population density effects on feeding activity of Stomoxys calcitrans (Diptera: Muscidae) on cattle.

The relationship of population density and temperature to feeding activity of stable flies, Stomoxys calcitrans (L.), on cattle was studied by placing cattle in constant temperature chambers with controlled fly density and temperature. The number of flies per front leg declined within hours after release but increased with fly density and temperature. The time flies spent on the host during a 5.5-h exposure period ranged from < 2.5 min at temperature < 16 degrees C to > 34 min when temperature was > 20 degrees C. Estimates of the temperature threshold for flight ranged from 10.7 to 20.1 degrees C and were influenced by density and time after release. Nearly 45% of the feeding flies were on the front legs, and this proportion was unaffected by density, temperature, and time after release. In the field, the number of flies per foreleg also was influenced by density and temperature. Estimated flight threshold was 10.7 degrees C, low enough to allow flight during 41-95% of the daylight hours from May through October in southern Alberta.