Maybe we had gathered the whole mosquito product of many acres. This is shown by the facts that if one rushes through thick bushes for a distance, into a clear space, the mosquitoes seem absent at first. One must wait a minute or so to gather up another legion. When landing from a boat on the Northern Lakes there are comparatively few, but even in a high wind, a walk to the nearest hilltop results in once again moving in a cloud of tormentors.
How does this paragraph refine the author’s idea about mosquitoes?