On a Migration of Tarnetrum corruptum (Hagen) (Odonata) in Western Oregon

Extract

On the warm afternoon of August 29, 1948, as I was walking through a wheat stubble-field on my farm located six miles southwest of McMinnville, Oregon, I became aware that I was in the midst of a dragonfly migration. I could see them all about me for a radius of perhaps seventy-five feet which was about the limit of my vision for an insect of this size. When first seen there was a considerable number passing toward the west with from thirty-five to fifty of the insects visible at any given moment but after about five minutes they began to thin out until only a few were visible. I then walked south for two hundred feet at which place another heavy concentration was encountered. After a short interval these thinned to a few stragglers. Thinking that the migration was about over I retraced my steps only to meet with another wave. It soon became apparent that the migration was taking place orer a wide front and that the insects tended to fly in groups over the valley floor.