Modeling visual-based pitch, lift and speed control strategies in hoverflies

<div><p>To avoid crashing onto the floor, a free falling fly needs to trigger its wingbeats quickly and control the orientation of its thrust accurately and swiftly to stabilize its pitch and hence its speed. Behavioural data have suggested that the vertical optic flow produced by the fall and crossing the visual field plays a key role in this anti-crash response. Free fall behavior analyses have also suggested that flying insect may not rely on graviception to stabilize their flight. Based on these two assumptions, we have developed a model which accounts for hoverflies´ position and pitch orientation recorded in 3D with a fast stereo camera during experimental free falls. Our dynamic model shows that optic flow-based control combined with closed-loop control of the pitch suffice to stabilize the flight properly. In addition, our model sheds a new light on the visual-based feedback control of fly´s pitch, lift and thrust. Since graviceptive cues are possibly not used by flying insects, the use of a vertical reference to control the pitch is discussed, based on the results obtained on a complete dynamic model of a virtual fly falling in a textured corridor. This model would provide a useful tool for understanding more clearly how insects may or not estimate their absolute attitude.</p></div

Eagle Lake Pollution Control Project

This report describes the cooperative efforts that a lake community and several governmental agencies undertook to alleviate increasing cultural eutrophication in Eagle Lake, Kandiyohi County, Minnesota. Two non-point nutrient sources were identified: agricultural runoff and domestic sewage. A lake-encircling collection line now diverts the sewage to a treatment plant. Earthen dams with soil absorption fields have been tested as a means of removing nutrients from part of the watershed runoff. Coincident with initiation of these anti-pollution measures, a comprehensive research project was initiated. Detailed studies of the chemical, physical, and biological conditions in the lake were conducted before the sewage system was completed. Water and nutrient budget estimates have been made. Eagle Lake can be classified as moderately eutrophic. Socio-economic surveys of lakeshore residents, other watershed residents, and non-resident ice fishing users resulted in a base line data profile of recreation use of Eagle Lake and of attitudes toward the lake and toward the anticipated improvements. Hopefully these data will suggest a model of community action. These benchmark studies, while of intrinsic interest, will reach their ultimate utility as a reference for comparison with conditions in the watershed after the pollution control measures have been in operation. Such further studies are anticipated.Water Resources Research Cente