GRASSHOPPER GLACIER OF MONTANA — GURNEY 319 



August 1. Flights occurred both near ground level and at considerable 

 altitudes. The grasshoppers usually fly into the wind, unless it is too 

 strong to make headway against it. Winds which approach 10 

 miles per hour are probably strong enough in most instances to stop 

 the grasshoppers or effect a change of direction. Since it is well 

 known that air currents play an important part in the spread of in- 

 sects, I consulted Weather Bureau records covering the period im- 

 mediately prior to August 1, 1949, for the area concerned. Through 

 the kind cooperation of several Weather Bureau officials, it can be 

 stated that apparently the meteorological conditions on and just 

 before August 1 favored a movement to the glacier from the southwest. 

 On July 29-30 there was a 10-mile wind over southern Idaho blow- 

 ing toward the east and northeast; this was strongest at high levels 

 and may have carried the grasshoppers eastward. On July 31 there 

 were strong eastward-blowing winds at 12,000 feet and above, weaker 

 below. Over eastern Oregon on July 30 there was a 10- to 20- 

 mile wind toward the northeast at 10,000 feet above sea level. (The 

 base level of much of southeastern Oregon is 5,000 to 6,000 feet above 

 sea level.) Reports from Boise, Idaho, and Ogden, Utah, indicate 

 strong upward convection currents over southern Idaho July 30-31. 



Archer B. Carpenter, supervising forecaster of the Salt Lake City, 

 Utah, office of the Weather Bureau wrote (letter of September 8, 

 1949) : "Several days prior to August 1, 1949, the winds at 10,000 

 feet (above sea level) were sufficient to carry the grasshoppers from 

 southeastern Oregon into southern Montana if they were able to reach 

 that altitude. Winds below 10,000 feet were of a similar pattern but 

 lower velocities, and at higher altitudes a similar pattern but usually 

 higher velocities." 



One of the Grasshopper Glacier collectors, Mr. Hall, has reported 

 to me his conversation with an air-line pilot who at about the same 

 time saw a swarm of grasshoppers while he was flying in the vicinity 

 of eastern Oregon. The circumstances suggested that the species 

 might be rugglesi. 



OTHER LONG-DISTANCE MOVEMENTS OF GRASSHOPPERS BY AIR 



In considering the possibilities of a several-hundred-mile flight of 

 rugglesi to Grasshopper Glacier, probably aided by air currents, it is 

 helpful to review records of long flights by other species. These 

 records show that flights of several hundred miles actually occur when 

 circumstances are favorable. An example for which weather condi- 

 tions were known and apparently times and points of departure and 

 arrival also, is that discussed by Waloff (1946) for the desert locust 

 of Africa, Schistocerca gregaria. Many individuals of this grass- 

 hopper were found in Portugal October 12, 1945, and the circumstan- 

 tial evidence, which Waloff explains in detail, and which I have sum- 



